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Nutrition

NUTRITION

NUTRITION. Food is comprised of nutrients that are classified by their role in the body: the energy-yielding macronutrients (carbohydrates, protein, and fat), the essential micronutrients (vitamins, minerals, and water), and numerous other components. Although micronutrients do not supply energy to fuel the body, they are indispensable for the proper functioning of the metabolic and regulatory activities in the body. Other nonessential nutrients, such as flavonoids, phytoestrogens, carotenoids, and probiotics, also may have important health-promoting properties, and investigations are ongoing. The daily intake of a variety of foods provides energy and nutrients that are essential to the health and well-being of an individual. The relationships among food intake, nutrition, and health define the field of nutrition. More fully, nutrition is the study of food, its nutrients and chemical components, and how these constituents act and interact within the body to affect health and disease.

The scope of the field has grown in recent years and the boundaries between the science of nutrition and many other biological sciences have blurred. For example, the science of nutrition includes chemistry to study how food ingredients interact with each other; physiology to investigate how nutrients within food are assimilated into body tissues; engineering to design new fortified foods; anthropology to explore why we chose to eat certain foods in centuries past; and psychology to determine what attitudes and behaviors influence our dietary patterns today. Nutritionists often have either a college or advanced degree in nutrition or a related field, whereas clinical (human) nutrition specialists will have graduate degrees, which may include medicine, and have completed an examination for certification. Registered dietitians are nutrition professionals who are often responsible for applying nutritional science to clinical practice to promote health and treat disease. Dietitians frequently work in hospitals but also may be employed in universities, public health departments, restaurants, the food industry, and exercise facilities. Similarly, given the broad scope of the field, other nutrition professionals include but are not limited to physicians, biochemists, anthropologists, epidemiologists, geneticists, food scientists, and engineers.

For this review, the field of nutrition is divided into three major categories: (1) nutrition in research, (2) nutrition in clinical practice, and (3) nutrition in policy and education. An overview of nutritional research is presented, from how nutrients interact within the body and among themselves (nutritional biochemistry), to the investigation of the relationships between specific foods or food groups and the health status of populations (nutritional epidemiology). Research findings in the field provide the information needed to guide nutrition practice for the care of individuals as well as large groups of people. The development of nutrition policy comes from both research and clinical practice advances. Concise descriptions of each are given and a brief history of the field and projected directions of the future of the field are offered.

Nutrition: A Historical Perspective

Numerous advances in the field of nutrition have occurred within the last century. The major focus of nutrition research and practice shifted from concern over which foods are required to avoid nutritional deficiencies and overt illness, to what foods and supplements may be consumed to promote optimal health. Functional foods are a part of the vocabulary, and energy bars, herbal remedies, and nutritional supplement products are now widely available.

In biblical times certain foods were understood to have special healing properties; however, the concept of nutrients as essential for health is relatively new. Recent discoveries in the field have been dependent on the development of scientific methods to analyze nutrient content and interactions. Therefore, though some vitamins were understood to be essential in the early part of the twentieth century, trace elements such as zinc and selenium were not considered essential for humans until the 1970s.

As the field of nutrition has developed, it has also expanded. In 1950 the history of nutrition science during the two previous centuries was summarized by Dr. Elmer McCollum in just under five hundred pages. It would likely take ten volumes of such texts to encapsulate the nutrition-related findings and proceedings from the latter half of the twentieth century. Accomplishments in the field of nutrition over the last century are highlighted in five major eras: (1) food as energy, (2) micronutrient deficiency diseases, (3) nutrition in public policy, (4) nutrition and chronic disease, and (5) nutrition for optimal health.

Food as energy (18801920). By the end of the nineteenth century the major, energy-yielding components of foodprotein, fat, and carbohydratehad been identified, and nutrition research, especially concerning the metabolism of proteins and the energy composition of foods, was flourishing. Much of this work had been conducted in animals; therefore, the human nutrition experiments performed by Dr. W. O. Atwater (18441907) and colleagues were particularly novel. From their studies, the energy yield of carbohydrate, protein, and fat was derived (4, 4, and 9 kcal per gram, respectively), values that are still used today. Dr. Atwater also developed the first human calorimeter in the United States to measure energy expenditure. However, it was a pair of medical doctors, James Harris and Francis Gano Benedict, who perfected this methodology to establish standards for the energy needs of healthy individuals. Energy expenditure was measured in approximately 250 healthy men and women at the Carnegie Institute Laboratory in Washington, D.C., and equations were derived from the data. The Harris-Benedict energy expenditure prediction equations for men and women, published in 1919, remain some of the most useful tools in clinical nutrition assessment today.

Micronutrient deficiency diseases (19201940). The period between 1920 and 1940 brought about a paradigm shift in the understanding of the etiology of some common diseases. Until this time it was thought that all disease resulted from poor sanitation and hygiene; therefore, bacteria, mold, and toxins were identified as the likely cause of disease. As Alfred Harper has suggested, "the concept that a disease might be caused by a deficit of a substance that was nutritionally essential was beyond the grasp even of most nineteenth-century physicians and scientists" (p. 217). In order to combat disease as well as increase shelf life, food was sterilized, milled, and polished to reduce the danger of ingesting bacteria, mold, and toxins. Despite these efforts, pellagra, beriberi, and infantile scurvy actually increased in prevalence. In a number of studies conducted by Dr. Joseph Goldberger from 1914 to the 1920s, where the diets of individuals suffering from pellagra were compared to those of healthy individuals, foods that decreased the presence of diarrhea and dementia in pellagrous individuals were identified. From his work it was later determined that pellagra was due to a diet poor in the vitamin niacin and not infection. At approximately the same time, Dr. Christiaan Eijkman (18581930) won a Nobel Prize in medicine (1929) for the discovery of the "antineuritic" vitamin thought to be responsible for curing beriberi. Through his experiments, in which chickens were fed human hospital diets, combined with studies of beriberi in prisoners who survived on polished rice, he hypothesized that the hull of the rice grain contained an antidote to the neurological disorder. Although not completely correct, his observations led to the discovery of the essential vitamin thiamin.

As Kenneth J. Carpenter summarized, "new technologies of food processing that have obvious advantages may also have a downside" (p. 227). While technology decreased infectious disease and increased the shelf life of food products, it inadvertently led to nutritional deficiencies. The heat-sterilization of cow's milk, which destroyed vitamin C, was related to the outbreak of infantile scurvy in well-to-do families. The practices of polishing rice and degerming corn to increase grain stability also led to increased prevalence of beriberi (thiamin deficiency) and pellagra (niacin deficiency), respectively.

Nutrition in public policy (19201964). One of the most fruitful periods in the history of public health nutrition followed on the coattails of World War I. It became possible to manufacture the micronutrients that had been identified by chemists as essential for health cheaply and efficiently. In 1922 the first of a series of public health efforts at eradicating nutrient deficiency in the United States was initiated by the voluntary addition of iodine to salt (see Table 1). The fortification of other foods was used to address rampant public health problems such as rickets (vitamin D), beriberi (thiamin), pellagra (niacin), and dental caries (fluoride). Since the initiation of fortification policies in the United States, clinically evident nutritional deficiencies have been virtually eliminated.

The first attempt at defining nutritional requirements was directed toward the prevention of nutrient deficiencies in military personnel during World War II. In the early 1940s the Food and Nutrition Board of the National Academy of Sciences reviewed the scientific evidence and developed the Recommended Dietary Allowances for energy, protein, and eight essential vitamins and minerals. The first national food supplementation program was initiated in 1946 (National School Lunch Act) to improve the dietary intake of children from economically disadvantaged families. Other national food assistance programs were added over the next fifty years.

Nutrition and chronic disease (19601990). The last forty years of the twentieth century saw continued discovery in the field of nutritional biochemistry and a new research emphasis on the role of nutrition in the cause of and treatment for chronic disease. Disease patterns shifted from infectious and nutrient deficiency diseases to increasing rates of cardiovascular disease, diabetes, cancer, and osteoporosis. Nutrient deficiencies, when present, were often secondary to restrictive dietary habits, economic deprivation, or the presence of another disease that altered nutrient metabolism. The more pressing problem now was the change in the American lifestyle and a dietary shift from too little to too much. Modern household technologies increased productivity in housework but decreased physical activity, and the home-cooked family meal became a thing of the past. Varied diets consisting of whole grains, fruits, and vegetables gave way to convenience foods resulting in a much higher consumption of fat and sugar. Results from the Framingham Heart Study were perhaps the first glimpse into the relationship between fat intake and cardiovascular disease and the realization that each type of fat plays a specific role in health and disease. During this era, links among fat intake, serum cholesterol, and cardiovascular disease were studied thoroughly, and the reasons for the increasing prevalence of obesity in the United States were explored. In 1985 Michael Brown and Joseph Goldstein were awarded the Nobel Prize in medicine for their work on the regulation of cholesterol metabolism and its influence on arteriosclerosis.

The essentiality of macrominerals (e.g., calcium, phosphorus, sodium) was understood in the 1850s. However, it was not until technological advances triggered an explosion of new research that trace and ultra-trace elements were identified as essential for humans. Working together, nutritionists, biochemists, biologists, immunologists, geneticists, and epidemiologists uncovered the mysteries behind minerals such as zinc, selenium,

Significant policies and recommendations in nutrition (19012001)
Date Nutrition policies and recommendations Description
1917 Food Guide, "5 Food Groups" Food groups included flesh foods, breads/cereals, butter/fats, fruits and vegetables, and sweets (USDA).
1922 Iodine fortification Iodized salt was initially added to salt (60 mg/g salt) in Michigan, goiter virtually eradicated by 1927.
1932 Vitamin D fortification Vitamin D was added to milk at a minimum of 400 IU/quart. Was also added to some margarine.
1941 Enrichment with iron, niacin, riboflavin, and thiamin Iron, niacin, riboflavin, and thiamin were added to refined wheat flour, and eventually to bread, pasta, rice, and cereal grain products.
1943 Recommended Dietary Allowances, 1st edition (United States) Purpose: "To serve as a guide for planning an adequate diet for every normal person." (FNB/NRC)
1945 Fluoride fortification Voluntary artificial fluoridation of municipal water supply in the United States; currently, 62 percent of U.S. population drinks fluoridated water.
1946 Food Guide, "Basic 7" Food groups included milk, meat, green/yellow vegetables, citrus fruits, potatoes/other vegetables, bread/cereal, and butter/margarine (USDA).
1946 National School Lunch Act It provides nutritionally balanced, low-cost, or free lunches to nearly 27 million children each school day. The program was established under the National School Lunch Act, signed by President Harry S Truman.
1958 Daily Food Guide, "Basic 4" Food groups included meat/eggs/fish, milk/dairy, fruit/vegetables, and bread/cereals (USDA).
1964 Food Stamp Act The first Food Stamp Act was started as a pilot project in 1961. The current law was enacted in 1977 and is amended regularly by the Congress. Purpose is to end hunger and improve nutrition and health. It helps low-income households buy food for a nutritionally adequate diet.
1975 National School Breakfast Program The School Breakfast program began as a pilot project in 1966 under the Child Nutrition Act. The purpose was to ensure that all children have access to a healthy breakfast at school to promote learning readiness and healthy eating behaviors. It provides nutritionally balanced, low-cost, or free breakfasts to 7.4 million children each school day.
19711974 National Health and Nutrition Examination Survey (NHANES) The first of a series of surveys to assess the health and nutritional status of the U.S. population (NCHS/CDC).
1974 Special Supplementary Nutrition Program for Women, Infants, and Children (WIC) Nonentitlement program designed to improve the intake of protein, vitamins A and C, calcium, and iron, to low-income, pregnant, and lactating women and children less than 5 years old.
1980 Dietary Guidelines for Americans: Nutrition and Your Health First set of recommendations for individuals to guide food choices without specifying amounts (USDA/DHHS).
1985 Continuing Survey of Food Intakes of Individuals (CSFII) The first of a series of surveys to provide information on the dietary status of the U.S. population and monitor changes in dietary intakes (ARS).
19881994 NHANES III National Health and Nutrition Examination Survey, noted the significant increase in obesity in the United States (NCHS/CDC).
1989 RDA, 10th edition Definition: the level of intake of essential nutrients that . . . meet the known nutrient needs of practically all healthy persons.
1989 VI. Diet and Health: Implications for Reducing Chronic Disease Risk Thorough review of the evidence on which dietary guidelines are based. Specific evidence provided on intake of fat, fruit and vegetables, protein, salt, alcohol, calcium, fluoride, and physical activity (FNB).
1990 VII. Nutrition Labeling and Education Act (NLEA) This act made standardized nutrition labeling on food products in the United States mandatory. There are now 11 health-related claims that are approved to be used in advertising on food packages (FDA).
1992 Food Guide Pyramid Eating guide based on the RDA that also considered salt, fat, and sugar intake (USDA/HNIS).
1994 Dietary Supplement Health and Education Act (DSHEA) Exempts any product labeled as a dietary supplement from FDA regulatory approval. Permits structure/function claims without prior FDA authorization.
1997 Dietary Reference Intakes (DRI) This was the first in a series of revised recommendations now called DRI, which replaces the RDA. This report included recommendations for calcium, phosphorus, magnesium, vitamin D, and fluoride.
1998 Folate fortification Fortification of all breads, pasta, rice, flour, and breakfast cereals with folate to decrease the risk of neural tube defects in women of childbearing age. Program initiated in United States, Mexico, and Canada.
1998 Dietary Reference Intakes (DRI) Second series of the DRI for thiamin, riboflavin, niacin, vitamins B6 and B12, folate, pantothenic acid, biotin, and choline.
2000 Dietary Guidelines for Americans, 4th edition The dietary guidelines are updated about every 5 years. They provide nontechnical suggestions for healthy dietary patterns and activity (USDA/DHHS).
2001 Dietary Reference Intakes (DRI) Third series of the DRI for vitamins A and K, arsenic, boron, chromium, copper, iodine, iron, manganese, molybdemum, nickel, silicon, vanadium, and zinc.

copper, molybdenum, and chromium. Scientists first recognized human zinc deficiency in the mid-1960s. Severely growth-retarded, young Middle Eastern men were anemic, extremely lethargic, and hypogonadal. Their diet consisted mainly of wheat bread with little animal protein. When their diets were supplemented with zinc, their lethargy, growth, and genital development improved.

Nutrition for optimal health (1990present). In the understanding of nutrition, the American public experienced yet another paradigm shift in the 1990s. They wondered if all nutrients that provided a health benefit needed to fit the traditional definition of "essential nutrient." As a result of this question, herbal and botanical extracts, phytochemicals, and other alternative nutritional therapies to promote optimum health were explored. In 1999 the U.S. market for functional foods alone was estimated to be $6 billion (Hasler, p. 504) and it continues to grow by approximately 12 percent each year. The explosion of this market is likely due to the increase in social acceptance, changes in regulations, the booming economy of the 1990s, and the targeting of products to particular populations. The scientific validation of some therapies also is of increasing interest.

Pharmacological uses (larger amounts than required to prevent deficiencies) of essential nutrients are being explored. Although much of the current interest in megavitamin supplementation began in the 1990s, the work of Dr. Linus Pauling in the 1970s initiated the movement. Pauling was the only individual to be awarded two unshared Nobel prizes for his work in chemistry (1954) and peace (1962). In the field of nutrition, however, he is noted most for his unproven theories regarding the potential protective role of vitamin C on the common cold, cancer, and heart disease. Pauling himself reportedly took up to six hundred times the recommended daily amount of vitamin C. Given that many individuals also practice a "more must be better" approach, the national recommendations for nutrient intake now include guidelines for safe upper limits for individual nutrient intakes.

Nutrition in Research

Experimental nutrition research is one aspect of the science of nutrition. Nutrition research is conducted to answer questions raised both in clinical practice and policy. Research in nutrition can focus on individual cells, whole animals or humans, or entire populations, and often overlaps with research in genetics, biochemistry, molecular biology, toxicology, immunology, physiology, and pharmacology.

Nutritional biochemistry. Nutritional biochemistry is the backbone to the understanding of the structure and function of nutrients within food and the body. Nutrients serve as cofactors for enzymes, components of hormones, and participants in oxidation/reduction reactions through metabolic processes. Though required in small amounts, nutrients are essential for body growth, sexual development and reproduction, psychological well-being, energy level, and the normal functioning of most organ systems in the body. Nutritional biochemists study the functional roles of vitamins and minerals in the body, metabolic blocks that occur from deficiencies, the effects of hormones on nutrient metabolism, and interactions among nutrients within the body. In the 1990s a whole new area of research emerged that focuses on relationships between nutrition and genetics. An example of this type of study includes the identification of a genetic defect in folate metabolism (C677T), which increases a woman's risk of delivering a baby with a neural tube defect.

Food science. Food science is the study of the composition of food materials and the reaction of food to processing, cooking, packaging, and storage. Food science integrates knowledge of the chemical composition of food materials; their physical, biological, and biochemical behavior; the interaction of food components with each other and their environment; pharmacology and toxicology of food materials, additives, and contaminants; and the effects of manufacturing operations, processes, and storage conditions.

The potential beneficial role of functional foods in the American diet has gained attention and recent food science research focuses on the development of such foods. Functional foods are generally defined as those that provide health benefits beyond basic nutrition, and include fortified, enriched, or enhanced foods, and whole foods, which have high levels of protective nutrient components. Examples of these foods include orange juice with added calcium or echinacea, or snack foods with antioxidants, fruit-flavored candy with vitamin C, various soy products, and margarine with added plant sterols. Factors that drive the market for such foods include a growing general public interest in nutrition and its impact on health, an aging population that is more concerned with health, research findings receiving media attention, and an increasingly unregulated consumer food market.

Human nutrition. Human nutrition, or clinical nutrition, research is that which focuses on the study of nutrients within the living human body. Although biochemical studies are extremely informative, until the nutrient is added to or depleted from the diet, the effects on individuals can only be hypothesized. Human nutrition research includes the study of individual nutrient requirements (e.g., nutrient intake assessment, energy expenditure assessment, nutrient turnover balance studies, and nutrient bioavailability), the effects of nutrients on body growth (e.g., body composition techniques, anthropometry, pubertal assessment), and the dietary, physiological, or disease factors that influence nutrient requirements. In the 1990s one important human nutrition study found that increasing folic acid intake in young women reduces the incidence of neural tube defects (spina bifida) in their babies.

Nutritional epidemiology. Nutritional epidemiology is the science of systematically studying the relationships between food choices and health status. Epidemiological studies are particularly valuable in understanding complex relationships between food intake (dietary exposure) and determinants of diseases with multiple etiologies and long latent periods. Examples of such studies include the relationships between low folic acid intake and increased incidence of spina bifida, and elevated saturated fat intake and elevated risk of arteriosclerosis. There are, however, limitations to these studies in that they describe relationships rather than prove cause and effect. Frequently, clinical trials and intervention studies are used as follow-up studies to evaluate more fully the questions raised by epidemiological evidence.

Nutrition in Clinical Practice

Scientific evidence continues to mount regarding the key roles that nutrients and their metabolism play in the prevention of the most common chronic diseases. Half of the leading causes of death in the United States (heart disease, cancer, stroke, and diabetes) are associated strongly with unhealthy eating habits. Clinical nutrition is the practice of applying research evidence to aid in the care of individuals with or at risk for diet-related diseases. These principles are used to develop individualized nutrition care plans. Generally, diseases may affect nutritional status by (a) decreasing the intake of nutrients, (b) altering the metabolism of nutrients (or unusual losses), or (c) altering energy expenditure. Alternatively, as mentioned briefly above, poor nutritional status can lead to disease. For example, zinc deficiency can decrease the function of the immune system that in turn leads to increased risk for diarrhea and infectious diseases.

Assessment of nutritional status is essential for identifying undernourished and overnourished states (obesity is now a major health problem) and estimating the optimum intake to promote normal growth and well-being. Nutritional assessment has several components, including the evaluation of dietary intake, growth status, body composition, energy expenditure, and biochemical measures of nutritional status in the context of a medical history, diagnoses, and current therapy. These data are used to develop individualized nutritional care plans, which may include recommendations for total energy intake, adjustments in the diet to increase or decrease the consumption of certain foods, and possibly the inclusion of nutrient supplements. For patients who cannot be fed orally, more technology-based nutritional support is used to maintain or improve nutrient intakes and nutritional status. This involves either feeding the patient through a tube directly into the stomach or intestine (enteral) or through an intravenous line directly into the bloodstream (parenteral). Because malnutrition will add to complications of illness and prolong the illnesses and hospitalization, appropriate assessment of the patient is extremely important. In the complex and rapidly changing context of critical illness, individualized nutrition assessments are crucial and require the sequential monitoring of all patients to maintain appropriate nutritional care plans.

It is unlikely that individuals who have not been seriously ill have had the opportunity to seek the counsel of a trained nutritional professional for developing an individualized diet plan. The average American displays a keen interest in how nutrition affects his or her health, and is disappointed with the information physicians are able to provide because traditional medical training has limited nutrition content. Therefore, greater numbers of individuals are seeking nutrition information for themselves, and using the information to self-diagnose and self-prescribe. The advances in communications technology, particularly the explosion of information on the World Wide Web, allow the ready accessibility of sound nutritional advice, and substantial amounts of quackery. Without training and a significant amount of time dedicated to the task, it is difficult to decipher truth from fraud. Future directions in nutritional education likely will include tools to aid Americans in deciphering information, particularly from the Internet, in order to make educated choices to optimize their diets and live healthier lives (see Table 2).

Nutrition in Public Policy: Monitoring and Education

Nutrition in public health or nutrition policy generally is regarded as the combined efforts taken toward improving

Credible sources of nutrition information on the World Wide Web
Professional Organizations
American Dietetic Association: www.eatright.org
American Society for Clinical Nutrition: www.faseb.org/ascn
Society for Nutrition Education: www.sne.org
American College of Sports Medicine: www.acsm.org
Institute of Food Technologists: www.ift.org
Government Organizations
Centers for Disease Control: www.cdc.org
Office of Food Labeling: www.cfsan.gda.gov
Center of Food Safety and Applied Nutrition: www.vm.cfsan.fda.gov/list.html
Food and Nutrition Information Center: www.nal.usda.gov/fnic
Center for Nutrition Policy and Promotion: www.usda.gov/fcs/cnpp.htm
International Food Information Council: www.ificinfo.health.org
National Center for Complementary and Alternative Medicine: http://nccam.nih.gov/
Office of Dietary Supplements of NIH: http://odp.od.nih.gov/ods/
Private Organizations
Quack Watch: http://www.quackwatch.com/
Gatorade Sports Science Institute: www.gssiweb.com
National Dairy Council: www.dairyinfo.com
The Dannon Company: www.dannon.com
United Fresh Fruit and Vegetable Association: www.uffva.org

nutrition and health status of populations. With increasing emphasis on health promotion and disease prevention, there is a proliferation of nutrition-related disease prevention, screening, and education programs targeted at increasing fiber, fruit, and vegetable intake, and reducing saturated fat intake. Additionally, a number of food assistance programs and mandated food fortification programs have been instituted, all promoting a healthy diet and lifestyle.

Nutrition research, public policy programs, and nutrition surveillance systems work synergistically like spokes on a wheel. Evidence obtained from scientific research is used to set nutritional recommendations such as the Dietary Reference Intakes and the Dietary Guidelines for Americans. These standards are used to judge the adequacy of the American diet, provide the basis for nutrition labeling of foods, formulate special diets, and guide the development of food fortification and nutrition policy developed to assist those who are at nutritional risk. Specific food assistance programs (such as, food stamps, Special Supplementary Nutrition Program for Women, Infants, and Children) are targeted at specific economically disadvantaged and nutritionally at-risk populations. Fortification programs generally are less specific, but some target at-risk populations through specific foods, for example, vitamin Dfortified milk to prevent rickets in young children. Finally, the wheel is completed by nutrition monitoring programs that are used to evaluate the effectiveness of instituted policies. The National Health and Nutrition Examination Survey (NHANES) and the Continuing Survey of Food Intake of Individuals (CSFII) are ongoing monitoring tools used to assess the population's nutrient intakes, nutrition and health status, and knowledge and attitudes about health.

Perhaps most important, public health nutrition includes the dissemination of scientific findings, the explanation of dietary recommendations, and outreach of federal assistance programs. The responsibility of communicating experimental findings in an understandable form falls on nutrition scientists, journalists, educators, and the public. The scientists are responsible for interpreting the research findings into a form that is understandable to the general public. Journalists are responsible for communicating the scientific message in an objective way, and the public is responsible for pursuing an accurate understanding of the issues. Various government agencies have the responsibility to organize and administrate the myriad of nutritional policies and programs, and to communicate information regarding these programs to the public.

The Future of Nutrition and Food Science

In the twentieth century nutrition research, practice, and public policy shifted from a focus on the quantitative aspectsto ensure food security and eradicate nutritional deficienciesto a greater attention on the qualitative aspectsto achieve optimal, balanced, dietary intakes. In the twenty-first century nutrition research, practice, and policy will likely explore the following areas:
relationships between human genetics and nutrition, the role of genetically modified foods in human health,
the relationship of nonfood substances in the promotion of health and the bioengineering of functional foods,
the promotion of economic growth and food security in developing nations to prevent or delay the undesirable health effects of malnutrition, and
the prevention and treatment of the obesity epidemic in children and adults.

Relationships between food intake and human health will continue to be of great public interest, and nutrition and food scientists will face new challenges in a fasterchanging environment.

See also Assessment of Nutritional Status; Dietary Assessment; Dietary Guidelines; Dietary Systems: A Historical Perspective; Dietetics; Enteral and Parenteral Nutrition; Food Stamps; Functional Foods; Malnutrition; Nutrients; Nutritionists; Nutrition Transition: Worldwide Diet Change; Obesity; Physical Activity and Nutrition; Vitamins; WIC (Women, Infants, and Children's) Program.

BIBLIOGRAPHY

American Dietetic Association. "Position of the American Dietetic Association: Domestic Food and Nutrition Security." Journal of the American Dietetic Association 98 (1998): 337342.

American Dietetic Association. Nutrition and You: Trends 2000. Chicago, Ill.: American Dietetic Association, 2000.

Carpenter, Kenneth J. "Vitamin Deficiencies in North America in the 20th Century." Nutrition Today 34 (1999): 223228.

Committee on Diet and Health, Food and Nutrition Board, National Research Council. Diet and Health: Implications for Reducing Chronic Disease Risk. Washington, D.C.: National Academy Press, 1989.

Dupont, Jacqueline. "The Third Century of Nutrition Research PolicyShared Responsibility." Nutrition Today 34 (1999): 234241.

Food and Nutrition Board. Recommended Dietary Allowances. National Research Council Reprint and Circular Series No. 115. Washington, D.C.: National Research Council, 1943.

Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes. Washington, D.C.: National Academy Press, 1997. Studies on calcium, phosphorus, magnesium, vitamin D, and fluoride.

Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes. Washington, D.C.: National Academy Press, 1988. Studies on thiamin, riboflavin, niacin, vitamin B 6, folate, vitamin B 12, pantothenic acid, biotin, and choline. Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes. Washington, D.C.: National Academy Press, 2001. Studies on vitamins A and K, arsenic, boron, chromium, copper, iodine, iron, manganese, molybdemum, nickel, silicon, vanadium, and zinc.

Harper, Alfred E. "Nutritional Essentiality: Evolution of the Concept." Nutrition Today 34 (1999): 216222.

Hasler, Clare M. "The Changing Face of Functional Foods." Journal of the American College of Nutrition 19 (2000): 499S506S.

Intersociety Professional Nutrition Education Consortium. "Bringing Physician Nutrition Specialists into the Mainstream: Rationale for the Intersociety Professional Nutrition Education Consortium." American Journal of Clinical Nutrition 68 (1998): 894898.

McCollum, Elmer V. A History of Nutrition. Boston, Mass.: Houghton Mifflin, 1957.

Mertz, Walter. "Food Fortification in the United States." Nutrition Reviews 55 (1997): 4449.

Parascandola, Mark. "The History of Clinical Research." Journal of Clinical Research Practice 1 (1999): 720.

Shils, Maurice E, James A. Olson, Moshe Shike, and A. Catherine Ross. Modern Nutrition in Health and Disease, 9th ed. Philadelphia: Lippincott, Williams, and Wilkins, 2000.

Walker, W. A., and J. B. Watkins. Nutrition in Pediatrics, 2d ed. London: Decker, 1997.

Willett, Walter. Nutritional Epidemiology, 2d ed. Oxford: Oxford University Press, 1998.

Ellen B. Fung Virginia A. Stallings


Professional Nutrition Credentials in the United States

Certification Board Type of Certification*
Commission on Dietetic Registration DTR: Dietetic Technician (A.A., B.S., B.A.)
RD: Registered dietitian (B.S.)
CSP or CRD: Board certified specialist in pediatric or renal nutrition
FADA: Fellow of the ADA (R.D. and Ph.D., M.S.)
American Board of Nutrition Clinical Nutrition Specialist (M.D.)
Human Nutrition Specialist (Ph.D.)
National Board of Nutrition Support Certification CNSP: Certified Nutrition Support Physician (M.D.)
CNSD: Certified Nutrition Support Dietitian (R.D.)
Certification Board for Nutrition Specialists CNS: Certified Nutrition Specialist (Ph.D., M.S.)
* Type of education required for certification indicated in parentheses.
Italicized acronyms denote the professional credentials required for certification.


Definition of Terms

Nutrition: the study of foods, their nutrients, and other chemical components; their actions and interactions in the body; and their influence on health and disease.

Nutritional Science: the body of scientific knowledge that relates to the processes involved in nutrition.

Health: a state of optimal well-beingphysical, mental, and social; relative freedom from disease.

Functional Foods: foods that provide a health benefit beyond basic nutrition.

Essential Nutrient: a substance that must be obtained from the diet because the body either cannot make it or cannot make adequate amounts.

Enteral Nutrition: nutrient solutions delivered into the gastrointestinal tract (e.g., stomach, small intestine) through a tube inserted through the nose or directly into the stomach.

Parenteral Nutrition: nutrient solutions delivered directly into the bloodstream through an intravenous catheter.


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Nutrition

NUTRITION

Few subjects are more important to public health than food. One of the major ways in which humans interact with their environment is through our food. The science of nutrition has developed through the study of the components of foods that are required to sustain life and to maintain health. Improper diet can cause disease if important nutrients are missing from the diet, and inappropriate dietary practices can increase the risk of certain diseases.

Essential nutrients are substances that must be in the human diet to support life. These essential nutrients include vitamins, inorganic elements, essential amino acids, essential fatty acids, and a source of energy, and water. A lack of a nutrient or an insufficient amount of a nutrient can result in a deficiency disease that can be life threatening in extreme cases. The essential nutrients are widely distributed in foods and most people can obtain sufficient amounts of them if they consume a varied diet.

ELEMENTS OF HUMAN NUTRITION

Energy. Most of the food consumed is used by the body to supply energy. The body is able to digest and absorb into the blood stream components of carbohydrates, fats, and protein that can be metabolized by the body to release energy. Energy is used to maintain body temperature, support metabolic processes, and to support physical activity. People are generally in a state of energy balance, that is, they consume as much energy as they use to support their bodies and daily living. They tend to gain weight if they are in positive energy balance, or lose weight if they take in less than they expend. Most excess energy is stored by the body as fat. Energy needs are usually expressed in kilocalories, but in much of the world's scientific literature, energy expenditure is expressed in joules or kilojoules (1 kilocalorie equals 4.184 kilojoules).

The energy expended by the body when at rest is quite constant between individuals and can be

Table 1

Energy Expenditure during Selected Activities
Activity Kcal expended per hour 1
1These values represent above resting metabolic rate for a 70 kg person.
source: Powers, S. K., and E. T. Howley, eds. (2000). Exercise Physiology, 4th ed., New York: McGraw-Hill.
Walking, 2 to 2.5 miles per hour (mph) 185255
Walking, 5 mph 555
Jogging 5.5 mph 655
Tennis 400
Aerobic exercise 275
Cross country skiing 600

estimated quite closely by prediction equations that take into account age, sex, and body weight. The resting metabolic weight of a 70-kilogram (154-lb.) man, for example, is estimated to be 1750 kilocalories per day, and for a 58-kilogram (128-lb.) woman, 1350 kilocalories per day. The total daily energy needs are related to the amount of physical activity expended in the course of everyday life. A person whose life style involves light amounts of activity may have a total energy expenditure of about one and one-half times their resting metabolic rate, while a person who is engaged in very intense physical activity may expend over twice as much energy as their resting metabolic rate in the course of twenty-four hours. Exercise can increase the metabolic rate considerably, depending on the type and duration of the activity. The amount of energy expended by certain types of physical activity is shown in Table 1.

Protein. The principal structural components of body soft tissues are proteins, which are made by the body from amino acids. The amino acids along with the nucleic acids are the principle nitrogen-containing components of the body and of most foods. The enzymes that regulate most body processes are also proteins. The body can synthesize many of the amino acids needed for protein syntheses, but some amino acids must be obtained from the proteins in the diet. The dietary essential amino acids for humans are threonine, valine, leucine, isoleucine, methionine, lysine, histidine, and tryptophan. Two others can only be formed from essential amino acids: tryosine from phenylalanine, and cystine from methionine. Human dietary protein requirements are quite modest. An adult man of average weight is estimated to need about sixty-three grams of protein per day, while an average woman is estimated to need about fifty grams. The protein must supply the essential amino acids required by humans and sufficient total nitrogen to allow syntheses of the other amino acids required for protein synthesis.

Fats. Fats are synthesized from carbohydrates, but the body is unable to make certain fatty acids, which are components of fats. These essential fatty acids, notably linoleic and linolenic acid, must be supplied by dietary fats. Fats that are solid at room temperature, such as butter or lard, usually contain high amounts of saturated fatty acids such as palmitic or stearic acid. Fats that are liquid at room temperature such as vegetable oils are higher in unsaturated fatty acids, which include oleic acid as well as the linoleic and linolenic acid. Fat is the most concentrated source of energy available to humans, supplying about nine kilocalories per gram of dietary fat, compared to four kilocalories per gram of carbohydrate and protein. Fat is also the principal storage form of energy in the body.

Vitamins. Vitamins are a diverse group of dietary essentials that have important functions in the body. The vitamins known to be required by humans are listed in Table 2. Many of them are components of co-enzymes, molecules that are required for some enzymes to carry out certain metabolic processes. Others, such as vitamin E and vitamin C, act as antioxidants, protecting body components from damage from oxygen needed by the body for metabolism. Some are more like hormones, such as vitamin D, which regulates the absorption of calcium from the intestine and the formation of bones. Vitamin D can actually be formed by the action of ultraviolet light from the sun on vitamin D precursors found in the skin, but since this synthesis may not be sufficient at times, humans need a dietary source of vitamin D. Vitamin A is a component of visual pigments in the eye that respond to light stimuli and are essential for sight.

A deficiency of a vitamin may result in a characteristic deficiency disease related to the body function affected by the lack of the vitamin. Vitamin D deficiency can cause soft bones in children, a condition called rickets; vitamin A deficiency

Table 2

Vitamins and Inorganic Elements Required in Human Diets to Support Life and Maintain Health
Vitamins Inorganic Elements
source: Powers, S. K., and E. T. Howley, eds. (2000). Exercise Physiology, 4th ed., New York: McGraw-Hill.
Vitamin A (retinol, retinal, retinoic acid) Calcium
Phosphorus
Vitamin C (ascorbic acid) Potassium
Vitamin D (D3 cholecalciferol, D2 ergocalciferol) Sodium
Chlorine
Vitamin K (menaquinones, phylloquinone) Magnesium
Iron
Vitamin E (tocopherols) Iodine
Vitamin B6 (pyridoxine) Zinc
Vitamin B12 Selenium
Biotin Copper
Riboflavin Manganese
Niacin Chromium
Folacin Fluorine
Thiamin Molybdenum
Choline1 Boron
1Choline can be synthesized by the body but recent evidence suggests that dietary choline may be needed at some stages of the life cycle. In addition to these elements, substantial evidence indicates that arsenic, nickel, silicon, and vanadium have important physiological functions that may make them nutritional essentials. They are required in very small amounts and a dietary deficiency has not been convincingly described.

may cause night blindness and even blindness in its more severe form. Many of the vitamins have multiple functions in the body, and deficiency diseases can be severely debilitating in severe cases. Vitamins are required in very small amounts by the body. Only a few micrograms of vitamin B12is required each day, while vitamin C requirements may be from sixty to one hundred milligrams per day.

Inorganic elements. Humans also require several inorganic elements as components of the diet. The inorganic elements known to be required by humans are listed in Table 2. These elements may have a structural function, such as calcium and phosphorus, which are needed for bone synthesis, or they may have a catalytic function similar to some of the vitamins. They are required for the action of many enzymes in the body. Sodium and potassium are essential for fluid balance. Iodine is an essential component of thyroxin, the hormone produced by the thyroid gland. Some of the inorganic elements are required in extremely small quantities, only micrograms per day, while other elements may be needed in higher amounts. Soils vary in their content of some of the trace elements, and plants grown in some areas may be deficient in an essential element. This has been true for iodine, where a deficiency is still observed in many areas of the world, and selenium, where geographically based human deficiency disease has been observed.

NUTRITION RECOMMENDATIONS

In the United States, the National Academy of Sciences, through the National Research Council and The Institute of Medicine, has convened expert groups since 1941 to establish nutrition recommendations to be used by individuals and institutions for planning nutritionally adequate diets. These groups have established recommended dietary allowances (RDAs) as the daily dietary intake level for a specific nutrient that is sufficient to meet the nutritional requirements of nearly all (9798 percent) individuals in the life stage and gender group specified. In the most recent recommendations, dietary reference intakes (DRIs) have been specified that have attempted to estimate average nutrient requirements, RDAs, and an upper limit of safe nutrient intake. Where data are not sufficient to set a precise RDA, new recommendations called adequate intake (AI) define a recommendation for some nutrients.

The RDAs and AIs are used to plan diets for groups in hospitals, the military, large institutions, to set standards for government food programs such as school lunches, to establish nutritional labeling, and for counseling individuals. Similar dietary recommendations have been made by expert groups convened in many countries and also by international organizations such as the World Health Organization and the Food and Agricultural Organization of the United Nations. These recommendations are periodically revised to include information from most recent research findings. The latest recommendations for dietary reference intakes can be obtained in the United States from the National Academy Press, 2101 Constitution Avenue, NW, Washington, D.C. 20418.

Recommendations have been established for most nutrients where sufficient research data are available to make reliable estimates. The nutrient recommendations are given for different age groups and are differentiated by sexes because of different nutritional needs at different stages of life. Infants and young children who are growing rapidly have different nutrient needs compared to adults. Women who are menstruating need more iron to replace blood lost in the menstruation compared to postmenopausal women or men. Similarly, there are special needs for pregnant and lactating women. There is increasing evidence accumulating about the needs of the elderly, and nutrition recommendations now include a category for individuals over seventy years of age.

Recent revisions of nutrition recommendations have taken into account public health concerns about osteoporosis, a condition in which bone mineral is lost and older individuals become more vulnerable to bone fractures. New recommendations stress the importance of maintaining a high level (1200 mg/day) of calcium intake by both men and women over fifty years of age in an attempt to reduce loss of bone mineral. Similarly, recommendations for folic acid intake have also been revised to stress the importance of sufficient folic acid consumption by women who may become pregnant. Insufficient folic acid has been associated with a higher incidence of birth defects. The concern for adequate intake of folic acid led to the fortification of enriched grain products with folic acid in the United States beginning in 1998.

Nutrient recommendations also take into consideration the efficiency by which nutrients are digested and absorbed from foods. The form in which iron is ingested has a major influence on how much food iron is absorbed into the body. Iron in animal products is well absorbed because it is found as a component of hemoglobin or muscle pigments, while iron in plants, found as inorganic salts, is poorly absorbed. Some components of plants, such as phytic acid and tannins, also interfere with iron absorption. Therefore, dietary recommendations for iron intake must consider the availability of iron in the foods being consumed.

PUBLIC HEALTH ISSUES

In the early part of the twentieth century, nutritional disorders were common. Pellagra, a disease caused by a deficiency of nicotinic acid, was widespread in the southern United States. Rickets, from vitamin D deficiency, was common, and goiters from iodine deficiency were widespread. Iron-deficiency anemia and riboflavin deficiency were frequently observed. In parts of Asia, beriberi, a disease caused by thiamin deficiency, was a public health problem. The discovery and characterization of the vitamins made it possible to produce them in large amounts, and the enrichment of grain products with niacin, riboflavin, thiamine, and iron largely eliminated B-vitamin deficiencies in the United States as a public health problem. Similarly, the addition of vitamins A and D to milk provided protection from deficiency of the nutrients. The use of iodized salt essentially eliminated goiter from the U.S. population.

Unfortunately, nutritional deficiencies have not been eliminated from much of the world even today. A combination of poor diet, poor sanitation, and lack of safe water leading to frequent intestinal infections, causes more than 200 million of the world's children to be shorter and weigh less than children in good environments at the same age. These malnourished children are often born underweight from mothers who are also underweight and of poor nutritional status. Measures of the degree of malnutrition that are frequently used include a comparison of a child's weight for age, height for age, and weight for height with norms established by similar measurements on a well-nourished population of children. A usual convention classifies a child whose weight for age is more than two standard deviations below the standard as malnourished, and those three standard deviations below the standard are usually considered severely malnourished. The most vulnerable time for growth faltering in children is the period from six months of age to two years, when breast feeding stops and weaning foods are introduced. A combination of poor weaning foods, exposure to contaminated water, and poor sanitation that results in frequent bouts of diarrhea and the occurrence of other childhood diseases contributes to the poor growth of children after weaning.

The United Nations estimates that more than two-hundred million of the world's children are stunted, with the largest numbers being found in South Asia and in Africa. Similarly, about 4 percent of the world's population is considered at risk for iodine deficiency disorders including goiter, cretinism, and mental retardation. Vitamin A deficiency is estimated to affect about 3.3 million children in the world. Iron deficiency anemia is also the most prevalent nutritional deficiency in the world. Over 90 percent of those effected live in developing countries. The United Nations has estimated that severe anemia is a contributing factor to 50 percent of maternal deaths in developing countries.

Nutritional deficiencies are common in the refugees displaced by wars and natural disasters. Assistance is provided by the United Nations High Commissioner for Refugees to more than 26 million people world wide, and there are other internally displaced people in the world that may number as many as 31 million. The difficulty of providing food for these displaced groups puts them at risk for nutritional deficiencies.

Nutritional deficiencies are rare in most industrialized nations in Europe, Asia, and the Americas, and among the higher income groups of the developing world. The public health issues related to nutrition in these nations are concerned with overconsumption of energy, inadequate levels of activity, and improper food choices. Dietary practices are known to be risk factors for severe chronic diseases, including hypertension, atherosclerotic cardiovascular disease, and several types of cancers. The amount and type of fats seem to influence the risk of atherosclerotic cardiovascular diseases and to risk of certain forms of cancer. The consumption of saturated fatty acids and trans fatty acids found in certain hydrogenated cooking fats increases the levels of serum total cholesterol and cholesterol associated with serum low density lipoproteins (LDL) and thus increases the risk of artheriosclerosis and coronary heart disease. Diets high in fruits, vegetables, legumes, and cereal products are associated with a lower occurrence of coronary heart disease and certain cancers.

Genetic variations occur among individuals in their response to food. Variations in various blood lipoprotein components can effect an individual's response to dietary fat and cholesterol, and risk of coronary heart disease. There appears to be a genetic component to susceptibility to obesity. As more information is known about the human genome, it may be possible to predict more accurately individual risks for disease, and the dietary factors that may modify this risk.

Obesity. Dietary patterns that are characterized by the consumption of energy-rich, high-fat foods are considered to be factors contributing to obesity, particularly when the high intake of energy is not accompanied by appropriate physical activity. Obesity in adults is defined by reference to the body mass index (BMI), a relationship that takes into account both height and body weight. The BMI is calculated as weight in kilograms/height in meters squared. In pounds and inches it is calculated by weight (pounds)/height (inches)2× 704.5. A person with a body mass index between 20 to 25 is considered in the normal range, while a body mass index of 25 to 30 is considered overweight, and over 30 is considered obese.

The prevalence of obesity in the United States has increased markedly in recent years. The prevalence of overweight children ages six to eleven in surveys conducted in the early 1970s was 6.5 percent of males and 4.9 percent for females. By 19881994, the prevalence of overweight in this age grouping had increased to 11.4 percent and9.9 percent for males and females respectively. On the basis of surveys carried out between the years 1988 and 1994, more than 50 percent of American adults were considered overweight on the basis of having a BMI greater than 25. In further surveys, 17.9 percent of U.S. adults were considered obese in 1988, compared with 12 percent in 1991. The increasing prevalence of obesity is of considerable public health concern as excess weight is associated with greater risk of mortality, non-insulin dependent Type II diabetes mellitus, hypertension, stroke, osteo-arthritis, and some cancers. The annual number of deaths attributed to obesity in the United States has been estimated at more than 280,000 persons.

The control of obesity is difficult, and weight reduction is difficult to maintain. The most effective weight loss schemes seem to be those that reduce weight slowly, from one-half to one pound per week, and that involve both reduction in energy intake and an increase in physical activity. For overweight individuals, a reduced intake of from 300 to 500 kilocalories per day should result in a loss of one-half to one pound per week, while severely obese individuals may need to reduce energy intake by 500 to 1000 kilocalories per day to achieve a one to two pound per week weight loss.

Table 3

Dietary Guidelines for Americans
source: From the United States Department of Agriculture/Department of Human Services: Dietary Guidelines for Americans 2000.
Aim for fitness
  • Aim for a healthy weight
  • Be physically active each day
Build a Healthy Base
  • Let the Pyramid guide your food choices
  • Choose a variety of grains daily, especially whole grains
  • Choose a variety of fruits and vegetables
  • Keep food safe to eat
Choose sensibly
  • Choose a diet that is low in saturated fat and cholesterol and moderate in total fat
  • Choose beverages and foods to moderate your intake of sugar
  • Choose and prepare foods with less salt

Dietary guidelines. The concern for appropriate food choices have led many countries to issue dietary guidelines that provide advice that goes beyond the recommendations for individual nutrients covered by the recommended dietary allowances. The year 2000 dietary guidelines for Americans are shown in Table 3. These are issued by the U.S. Department of Agriculture and the U.S. Department of Health and Human Services and are revised about every five years. This publication represents the only official dietary advice to consumers by the U.S. Government. The full text of the bulletin provides more detailed advice on food choices. Many countries have published similar dietary guidelines to guide food choices to reduce the dietary risk factors associated with chronic disease.

To give advice to consumers regarding appropriate food choices to implement dietary guidelines, food guides have been developed. One of the most popular representations of a food guide is the dietary pyramid that has been published by the U.S. Department of Agriculture and the Department of Human Services. This food guide illustrates the importance of building a healthy diet on a base of cereal-based foods supplemented liberally with fruits and vegetables. Foods high in protein and fat should be consumed sparingly. The pyramid provides the number of recommended daily servings of the food groups.

Food supplies. The world population is projected to increase about 25 percent from the year 2000 to 2020, to about seven and one-half billion people. Most of this increase is projected to be in developing countries located in the tropical zones of the earth. The population of Asia is projected to increase by 800 million, and the population of Africa is projected to double. The International Food Policy Research Institute (IFPRI) has projected that food production will be able to increase such that the world per capita food available will supply about 2,900 kilocalories per person per day in the year 2020, compared to 2,700 kilocalories in 1993. The equitable distribution of food supplies will remain a major problem. The daily food available in sub-Saharan Africa is projected to supply only about 2,300 kilocalories per capita in the year 2020, barely sufficient to support a productive life. IFPRI estimates that one out of every four of the world's children will be malnourished in the year 2020. To achieve the projected increase in food supplies, continued improvements in crop yields will be necessary.

In contrast to the limited food supplies in many developing nations, developed countries are projected to have a food supply that will provide 3,470 kilocalories per capita per day in the year 2020. The U.S. Department of Agriculture indicates that the available food in the United States in 1994 provided 3,800 kilocalories per capita. This food supply provided annually 193 pounds of red meat, poultry, and fish, 585 pounds of dairy products, 194 pounds of cereal products, 151 pounds of fresh, canned, or dried fruits, 208 pounds of fresh, canned, frozen, dried, or fried vegetables and pulses, and 147 pounds of sugar. These figures represent food availability and do not represent actual consumption or account for wastes and losses in marketing and food preparation. Even with the variety of food available, consumers in the United States do not generally meet the dietary guidelines and food guide recommendations. For example, in food consumption surveys, only 38 percent of those surveyed reported consuming the recommended number of servings per day of cereals, 41 percent of the servings of vegetables (heavily weighted toward potatoes and starchy vegetables), and 23 percent of the servings of fruits. The reported diets provided 33 percent of the energy from fats and 11 percent from saturated fats. Food choices by consumers appear to depend on a variety of factors, such as cost, food preferences, convenience of preparation, and cultural norms, in addition to perception as to effects on health.

Food safety. In addition to providing nutrients, food can also potentially be a source of harm to a consumer. Hazards associated with food include microbiological pathogens, naturally occurring toxins, allergens, intentional and unintentional additives, modified food components, agricultural chemicals, environmental contaminants, and animal drug residues. It has been estimated that more than 80 million cases of food-borne illness occur annually in the United States, resulting in more than 9,000 deaths, primarily from microbiological contamination. The transformation of a safe food into a potentially dangerous one can occur anywhere in a food system that consists of producers, shippers, processors, wholesalers, retailers, and consumers.

An effective food safety system requires regulation, surveillance, consumer education, and continued research to detect and prevent food-borne illnesses. The increase in world trade in food also involves international dimensions in food safety issues. Import regulations dealing with food safety may also have the effect of restricting access to markets, and food safety becomes an issue in world trade.

The United States has a complex system of food-safety regulation. The Food and Drug Administration (FDA) is responsible for domestic and imported foods in interstate commerce except for poultry and meat products. The FDA has responsibility for standards for food labeling, inspects food-processing plants, and regulates food animal drugs and feed additives and all food additives. The Food Safety and Inspection Service (FSIS) of the U.S. Department of Agriculture (USDA) inspects meat and poultry products to ensure they are safe and correctly marked, labeled, and packaged. The Environmental Protection Agency (EPA) licenses pesticide products and establishes tolerances for pesticide residues in food products and animal feeds. The Centers for Disease Control and Prevention (CDC) are responsible for surveillance of illnesses associated with food consumption in association with the FDA and the USDA. These agencies also collaborate with state and local public health agencies that are concerned with food safety.

The consumption and preparation of food also has great social and cultural significance, contributing to the daily enjoyment of life. Public health concerns about dietary practices often must compete with these values as an individual makes food choices. This makes the issues associated with food and nutrition more complex than the medical and public health issues discussed here.

Malden C. Nesheim

(see also: Blood Lipids; Energy; Foods and Diets; Nutrition in Health Departments )

Bibliography

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(1997). Dietary Reference Intakes for Calcium, Phosphorous, Magnesium, Vitamin D, and Fluoride. Washington, DC: National Academy Press.

(1997). Dietary Reference Intakes: Thiamin, Riboflavin, Niacin, Vitamin B 6, Folate, Vitamin B 12, Pantothenic Acid, Biotin, and Choline. Washington, DC: National Academy Press.

Institute of Medicine, National Research Council (1998). Ensuring Safe Food. Washington, DC: National Academy Press.

Mokdad, H. H.; Serdula, M. K.; Dietz, W. H.; Bowman, B. A.; Marks, J. S.; and Koplan, J. P. (1999). "The Spread of the Obesity Epidemic in the United States 19911998." Journal of the American Medical Association 282:15191522.

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National Research Council, Food and Nutrition Board (1989). Recommended Dietary Allowances, 10th edition. Washington, DC: National Academy Press.

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United States Department of Agriculture and the United States Department of Health and Human Services (2000). Nutrition and Your Health: Dietary Guidelines for Americans. Home and Garden Bulletin no. 232, 5th edition. Washington, DC: United States Government Printing Office.

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Nutrition

Nutrition

Definition

The process by which humans take in and use food in their bodies; also the study of diet as it relates to health.

Description

Good nutrition in childhood lays the foundation for good health throughout a person's lifetime. With the proliferation of fast food restaurants, the number of junk food commercials on television, and the increased trend toward eating out, it is more difficult than ever for parents to ensure that their children maintain a nutritious diet. Across the last decades of the twentieth century, increasing affluence and the widespread availability of vitamin-enriched foods have shifted the focus of nutritional concerns in the United States from obtaining minimum requirements to cutting down on harmful elements in one's diet. Parents need to be as concerned about high levels of fat, cholesterol, sugar, and salt, as well as adequate intake of vitamins , minerals , and other nutrients.

The American Academy of Pediatrics, the National Academy of Sciences, the American Heart Association, and other health-care organizations agree that fat should not account for more than 30 percent of the calorie intake of children over the age of two, and saturated fat should account for under 10 percent. The main dietary sources in children's diets of saturated fat are whole milk, cheese, hot dogs, and luncheon meats. Recommendations for dietary change include switching to 1 percent or skim milk, low-fat cheese, and meats from which the fat can be trimmed. Since fat is important for growth, experts also caution that fat intake should not be under 25 percent of daily calorie intake and that parents of children under age two should not restrict fat in their diets.

The amount of refined sugar in children's dietstypically accounting for 14 percent of calorie intake by adolescenceis another cause for concern. Although sugar is known to cause tooth decay and also may be associated with behavior problems, the greatest danger in consuming foods high in added sugar is that these "empty calories" may replace the more nutritious foods that children need in order to maintain good health. (Soft drinks, perhaps the single greatest source of refined sugar in the diet of children and teenagers, get virtually all their calories from sugar and offer no nutrients.) This high intake of fat can lead to excess weight and, potentially, obesity .

Another element that needs to be restricted in children's diets is the intake of sodium through salted foods. Sodium has been closely linked to hypertension (high blood pressure), which increases a person's risk of heart disease and stroke . It has been determined that 18-year-olds need only 500 milligrams of sodium daily. In addition to limiting the amounts of fat, cholesterol, salt, and sugar in their children's diets, health authorities also recommend that parents concerned about nutrition ensure that children obtain a generous supply of complex carbohydrates (found in such foods as beans, potatoes, whole-grain products, and pasta) and have at least five servings of fresh fruits and vegetables daily.

Infancy

The first nutritional decision that must be made for a child by a parent or primary caregiver is whether to breastfeed or bottle feed. Breast milk is generally considered the best food for an infant up to the age of six to nine months. It has virtually all the nutrients that babies need and in the right balance. In addition, it contains important antibodies that help protect infants from infection at a time when their own immune systems are not yet fully developed.

The composition of breast milk actually changes during the first two weeks after a baby is born. Initially, it consists largely of colostrum, a substance that has more protein than complete breast milk and lower amounts of fat and sugar. It is also rich in the antibody immunoglobin A, which helps protect against infections. By the tenth day after birth, the regular breast milk, containing more carbohydrates and fat and less protein, is produced. The amounts of carbohydrates and fat gradually continue to increase, as will the quantity of the milk itself, to match the needs of the growing baby. Although most full-term infants get all the necessary nutrients from breastfeeding, some may need supplements of vitamins D and K.

Women who are either unable to breastfeed or who choose not to do so usually feed their babies formula made from processed cow's milk, generally reconstituted skim milk with vegetable oils added to substitute for the missing butterfat, which is difficult for infants to digest. Lactose (milk sugar) is also added, and some formulas contain whey protein as well. For infants who demonstrate sensitivity to cow's milk, formulas based on soy protein are available.

Breast milk or formula provides all the nutrients an infant needs up to the age of four to six months. Contrary to past beliefs, it has been found that not only do babies not need solid foods before then, introducing solids too early may lead to food allergies or overfeeding. Regular grocery-store cow's milk, which cannot be adequately digested by infants and can cause gastrointestinal bleeding, should not be introduced until a child is a year old. As the first solid food, pediatricians often recommend cereal made from a grain other than wheat, such as rice. The first solid foods may be either commercial baby food or strained foods prepared at home. Once solid foods have been introduced, infants still need to receive most of their nourishment from either breast milk or formula during their first year.

Toddlerhood

During children's second year, their growth rate slows dramatically compared to the prior period. In the first year, their birth weight triples, their length increases by 50 percent, and the size of their brain doubles. After that first year, it takes several years for their weight to even double. They will grow in spurts, with each spurt followed by a period of weight gain. This decreased growth leads to a decreased demand for food, often manifested in a newfound pickiness. As long as a child consumes an adequate, varied diet over a period of several days, parents are cautioned against becoming unduly concerned over a single day of unbalanced eating. Toddlers need to eat more than three times a day, either five or six small meals or three major ones with snacks in between.

Preschool

Preschoolers are still growing relatively slowly. Their weight increases about 12 percent between the ages of three and five, although their appearance changes considerably as they lose the baby fat of infancy and toddlerhood. They are still picky eaters, generally eating lessand less consistentlythan their parents would like. Although their fat requirement is not as high as that of infants, preschoolers still require more fat and fewer carbohydrates than adults. Fat is needed both for growth and for regulation of body temperature. Also, preschoolers need more than twice as much protein as adults. If the nutritional recommendations of the National Academy of Sciences are followed, a preschooler's diet will consist of 40 percent carbohydrates, 35 percent fats, 20 percent protein, and 5 percent fiber.

Between the ages of three and five, children's tastes expand considerably, and they are willing to consider foods they would have refused as toddlers. Four-year-olds can generally eat whatever foods the rest of the family is having. Preschoolers still cannot eat enough at three meals to meet their nutritional needs, and nutritious snacks are important. By this age, children's food choices can be strongly influenced by others. They will imitate good eating habits they see practiced by their parents, but they can also be easily swayed by television commercials for junk food.

School age

The diet of young school-age children, like that of preschoolers, should contain, in order of importance, carbohydrates, fat, and protein. A recommended proportion of these nutrients is 55 percent of the daily calorie intake from carbohydrates, 30 percent from fats, and 15 percent from protein. Once children begin spending a full day in school, a substantial, nutritious breakfast becomes more important than ever. Breakfast has been shown to affect the concentration and performance of elementary school children. Ideally, a balanced breakfast for a school-age child contains food high in protein as well as fruit and bread or another form of grain.

A major change affecting the nutrition of school-age children is the growth of opportunities to eat outside the home. The carefully packed homemade lunch may be traded for a salty snack or cupcake, and parts of it may be discarded. Vending machines and stores offer more temptations. In addition, school lunch programs differ widely in quality; even the nutritional value of a single food, such as a hamburger, can vary significantly depending on how it is prepared and what ingredients are used.

Adolescence brings its own set of nutritional needs and challenges. Beginning with the pre-teen years, children undergo their most intensive period of physical growth since infancy and need more food than at any other stage of life, particularly if they participate in sports . Teenagers, especially boys, are notorious for being able to empty the refrigerator of food, usually without gaining excess weight. Early adolescence in particular is a time of increased nutritional requirements for girls, who experience their greatest growth spurt at this time and also begin menstruating. It is difficult for weight-conscious teenage girls to eat enough to satisfy their minimum daily iron requirement of 18 milligrams, and they should try to eat either foods that are naturally rich in iron, such as turkey, beef, liver, and beans, or foods made from iron-enriched cereals. Adequate calcium intake is essential for the rapidly growing bones of teenagers, but milk has often been replaced by soft drinks as the beverage of choice among this age group. Parents should encourage adolescents, especially girls, to eat other foods rich in calcium, such as cheese, salmon, and broccoli.

As adolescents grow more independent, the number of meals and snacks eaten away from home increases as they spend more time with friends and take increased responsibility for arranging their own meals, with fast foods, soft drinks, and sweets often prominent on the menu. In addition to the natural appeal of these foods, peer pressure contributes to the choice of a diet soft drink over milk or juice, or pizza over broccoli. Although parents cannot control the eating habits of their teenagers, they can influence them by consistently making nutritious foods available at home and, at least in some cases, by discussing the benefits of good nutrition with them, especially if a relative or friend has had an illness, such as heart disease or colon cancer , that has known links to diet.

Common problems

A special problem that may affect childhood nutrition is the presence of food allergies , which are more common in children than in adults. They are most likely to begin when a child is very young and the immune system is still sensitive, usually in infancy. Food allergies also tend to run in families: if one parent has food allergies, a child has a 40 percent likelihood of developing one. This figure rises to 75 percent if both parents have food allergies. Common symptoms of food allergies include hives and rashes ; swelling of the eyes, lips, and mouth; respiratory symptoms; and digestive problems. Foods that most often produce allergic reactions in infants are cow's milk, soy products, and citrus fruits. Other common childhood allergens include wheat, nuts, chocolate, strawberries, tomatoes, corn, and seafood. In time, childhood food allergies are often outgrown. Feeding a child with food allergies is a challenging but not impossible task for parents. A variety of foods can be substituted for those to which a child is allergic: soy products for milk and other dairy products; carob for chocolate; and, in the case of wheat allergies, products or flour made from grains such as rice or oats.

Parental concerns

Vegetarian kids

About 2 percent of Americans ages six to 17 (about 1 million) are vegetarian, the same percentage as among American adults, and 0.5 percent are vegan, according to a 2002 survey by the Vegetarian Resource Group (VRG). Six percent of six- to 17-year-olds do not eat meat but eat fish and/or poultry. Teens who follow a vegetarian diet are more likely to meet recommendations for total fat, saturated fat, and number of servings of fruits and vegetables as compared to non-vegetarians. They also have higher intakes of iron, vitamin A, fiber, and diet soda, and lower intakes of vitamin B12, cholesterol, and fast food. Most teens, whether they are vegetarian or not, do not meet recommendations for calcium, according to the VRG survey. The study concluded that rather than viewing adolescent vegetarianism as a phase or fad, the diet could be viewed as a healthy alternative to the traditional American meat-based diet. The study also said that vegetarian diets in adolescence could lead to lifelong health-promoting dietary practices. The study was reported in the July-August 2002 issue of the VRG publication Vegetarian Journal.

Parents should closely monitor their vegetarian child's height, weight, and general health. A child who is not getting enough vitamins and nutrients may have symptoms such as skin rashes, fatigue, a painful and swollen tongue, irritability, pale skin, mental slowness, or difficulty breathing. The diets of vegetarian adolescents should be monitored closely to make sure they include a variety of foods, including fruits, vegetables, beans, whole grains, and non-meat protein sources. For vegetarians who do not eat fish, getting enough omega-3 essential fatty acids may be an issue, and supplements such as flax-seed oil should be considered, as well as walnuts and canola oil. Another essential fatty acid, omega-6, found in fish, can be obtained from borage oil or evening primrose oil supplements.

When to call the doctor

Parents should consult their child's pediatrician or physician if they are unsure the child's diet is nutritionally adequate. A doctor should also be consulted if a child's weight or height is not appropriate for their age.

KEY TERMS

Colostrum Milk secreted for a few days after birth and characterized by high protein and antibody content.

Essential fatty acid (EFA) A fatty acid that the body requires but cannot make. It must be obtained from the diet. EFAs include omega-6 fatty acids found in primrose and safflower oils, and omega-3 fatty acids oils found in fatty fish and flax-seed, canola, soybean, and walnuts.

Immunoglobin A A sugar protein with a high molecular weight that acts like an antibody and is produced by white blood cells during an immune response.

Resources

BOOKS

Evers, Connie Liakos. How to Teach Nutrition to Kids. Portland, OR: 24 Carrot Press, 2003.

Salmon, Margaret Belais. Food Facts for Teenagers: A Guide to Good Nutrition for Teens and Preteens. Springfield, IL: Charles C. Thomas Publisher Ltd., 2002.

Schlosser, Eric. Fast Food Nation: The Dark Side of the All-American Meal. Wilmington, MA: Houghton Mifflin Company Trade & Reference Division, 2001.

Shield, Jodie, and Mary Catherine Mullen. The American Dietetic Association Guide to Healthy Eating for Kids: How Your Children Can Eat Smart from Five to Twelve. Hoboken, NJ: Wiley, 2002.

PERIODICALS

Feskanich, Diane, et al. "Modifying the Healthy Eating Index to Assess Diet Quality in Children and Adolescents" 104 Journal of the American Dietetic Association (September 2004): 137583.

Mangels, Reed. "Good News about Vegetarian Diets for Teens" Vegetarian Journal (July-August 2002): 201.

Nicklas, Theresa A., et al. "Children's Meal Patterns Have Changed Over 21-Year Period: The Bogalusa Heart Study" 104 Journal of the American Dietetic Association (May 2004): 75361.

Nicklas, Theresa A., et al. "The Importance of Breakfast Consumption to Nutrition of Children, Adolescents, and Young Adults" Nutrition Today 39 (January-February 2004): 309.

Onderko, Patty. "The (Not So) Great American Baby Diet: A New Study Sheds Light on What Our Babies and Toddlers are Eating TodayAnd How You Can Improve Their Diet for Tomorrow" Baby Talk 69 (February 1, 2004): 45.

ORGANIZATIONS

American Dietetic Association. 120 South Riverside Plaza, Suite 2000, Chicago, IL 606066995. Web site: <www.eatright.org>.

International Food Information Council. 1100 Connecticut Ave. NW, Suite 430, Washington, DC 20036. Web site: <www.ific.org>.

WEB SITES

"Children's Nutrition Guide." Available online at <www.keepkidshealthy.com/nutrition> (accessed November 12, 2004).

"Kids Nutrition." Baylor College of Medicine. Available online at <www.kidsnutrition.org/> (accessed November 12, 2004).

Ken R. Wells

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Nutrition

Nutrition

Definition

Good nutrition can help prevent disease and promote health. There are six categories of nutrients that the body needs to acquire from food: protein, carbohydrates, fat, fibers, vitamins and minerals, and water.

Proteins

Protein supplies amino acids to build and maintain healthy body tissue. There are 20 amino acids considered essential because the body must have all of them in the right amounts to function properly. Twelve of these are manufactured in the body but the other eight amino acids must be provided by the diet. Foods from animal sources

FOODS HIGH IN SUGAR
Chewing gum
Chocolate bar
Chocolate milk
Fruit yogurt
Jelly beans
Ice cream
Liqueurs
Peanut butter and jelly sandwich
Pork and beans
Soda

such as milk or eggs often contain all these essential amino acids while a variety of plant products must be taken together to provide all these necessary protein components.

Fat

Fat supplies energy and transports nutrients. There are two families of fatty acids considered essential for the body: the omega-3 and omega-6 fatty acids . Essential fatty acids are required by the body to function normally. They can be obtained from canola oil, flaxseed oil, cold-water fish, or fish oil , all of which contain omega-3 fatty acids , and primrose or black currant seed oil , which contain omega-6 fatty acids. The American diet often contains an excess of omega-6 fatty acids and insufficient amounts of omega-3 fats. Increased consumption of omega-3 oils is recommended to help reduce risk of cardiovascular diseases and cancer and alleviate symptoms of rheumatoid arthritis, premenstrual syndrome, dermatitis , and inflammatory bowel disease .

Carbohydrates

Carbohydrates are the body's main source of energy and should be a major part of total daily caloric intake. There are two types of carbohydrates: simple carbohydrates (such as sugar or honey) or complex carbohydrates (such as grains, beans, peas, or potatoes). Complex carbohydrates are preferred because these foods are more nutritious yet have fewer calories per gram compared to fat and cause fewer problems with overeating than fat or sugar. Complex carbohydrates also are preferred over simple carbohydrates for diabetics because they allow better blood glucose control.

Fiber

Fiber is the material that gives plant texture and support. Although it is primarily made up of carbohydrates, it does not have a lot of calories and usually is not broken down by the body for energy. Dietary fiber is found in plant foods such as fruits, vegetables, legumes, nuts, and whole grains.

There are two types of fiber: soluble and insoluble. Insoluble fiber, as the name implies, does not dissolve in water because it contains a high amount of cellulose. Insoluble fiber can be found in the bran of grains, the pulp of fruit and the skin of vegetables. Soluble fiber is the type of fiber that dissolves in water. It can be found in a variety of fruits and vegetables such as apples, oatmeal and oat bran, rye flour, and dried beans.

Although they share some common characteristics such as being partially digested in the stomach and intestines and have few calories, each type of fiber has its own specific health benefits. Insoluble fiber speeds up the transit of foods through the digestive system and adds bulk to the stools, therefore, it is the type of fiber that helps treat constipation or diarrhea and helps prevent colon cancer. On the other hand, only soluble fiber can lower blood cholesterol levels. This type of fiber works by attaching itself to the cholesterol so that it can be eliminated from the body, preventing cholesterol from re-circulating and being reabsorbed into the bloodstream.

Vitamins and minerals

Vitamins are organic substances present in food and required by the body in a minute amount for regulation of metabolism and maintenance of normal growth and functioning. The most commonly known vitamins are A, B1 (thiamine ), B2 (riboflavin ), B3 (niacin ), B5 (pantothenic acid ), B6 (pyridoxine ), B7 (biotin ), B9 (folic acid ), B12 (cobalamin), C (ascorbic acid), D, E, and K. The B and C vitamins are water-soluble, excess amounts of which are excreted in the urine. The A, D, E, and K vitamins are fat-soluble and will be stored in the body fat.

Minerals are vital to our existence because they are the building blocks that make up muscles, tissues, and bones. They also are important components of many life-supporting systems, such as hormones, oxygen transport, and enzyme systems.

There are two kinds of minerals: the major (or macro) minerals and the trace minerals. Major minerals are the minerals that the body needs in large amounts. The following minerals are classified as major: calcium, phosphorus, magnesium, sodium, potassium, sulfur , and chloride. They are needed to build muscles, blood, nerve cells, teeth, and bones. They also are essential electrolytes that the body requires to regulate blood volume and acid-base balance.

Unlike the major minerals, trace minerals are needed only in tiny amounts. Even though they can be found in the body in exceedingly small amounts, they are also

very important to the human body. These minerals participate in most chemical reactions in the body. They also are needed to manufacture important hormones. The following are classified as trace minerals: iron, zinc, iodine, copper, manganese , fluoride, chromium, selenium , molybdenum, and boron .

Many vitamins (such as vitamins A, C, and E) and minerals (such as zinc, copper, selenium, or manganese) act as antioxidants . They protect the body against the damaging effects of free radicals. They scavenge or mop up these highly reactive radicals and change them into inactive, less harmful compounds. In so doing, these essential nutrients have been claimed to help prevent cancer and many degenerative diseases, such as premature aging, heart disease , autoimmune diseases, arthritis, cataracts, Alzheimer's disease , and diabetes mellitus .

Water

Water helps to regulate body temperature, transport nutrients to cells, and rid the body of waste materials.

Origins

Unlike plants, human beings cannot manufacture most of the nutrients they need to function. They must eat plants and/or other animals. Although nutritional therapy came to the forefront of the public's awareness in the late Twentieth century, the notion that food affects health is not new. John Harvey Kellogg was an early health food pioneer and an advocate of a highfiber diet . An avowed vegetarian, he believed that meat products were particularly detrimental to the colon. In the 1870s, Kellogg founded the Battle Creek Sanitarium, where he developed a diet based on nut and vegetable products.

Benefits

Good nutrition helps individuals achieve general health and well-being. In addition, dietary modifications might be prescribed for a variety of complaints including allergies, anemia , arthritis, colds, depression, fatigue , gastrointestinal disorders, high or low blood pressure, insomnia , headaches, obesity, pregnancy , premenstrual syndrome (PMS), respiratory conditions, and stress .

Nutritional therapy also may be involved as a complement to the allopathic treatments of cancer, diabetes, and Parkinson's disease . Other specific dietary measures include the elimination of food additives for attention deficit hyperactivity disorder (ADHD), gluten-free diets for schizophrenia , and dairy-free diets for chronic respiratory diseases.

A high-fiber diet helps prevent or treat the following health conditions:

  • High cholesterol levels. Fiber effectively lowers blood cholesterol levels. It appears that soluble fiber binds to cholesterol and moves it down the digestive tract so that it can be excreted from the body. This prevents the cholesterol from being reabsorbed into the bloodstream.
  • Constipation. A high-fiber diet is the preferred nondrug treatment for constipation. Fiber in the diet adds more bulk to the stools, making them softer and shortening the time foods stay in the digestive tract.
  • Hemorrhoids. Fiber in the diet adds more bulk and softens the stool, thus reducing painful hemorrhoidal symptoms.
  • Diabetes. Soluble fiber in the diet slows down the rise of blood sugar levels following a meal and helps control diabetes.
  • Obesity. Dietary fiber makes a person feel full faster.
  • Cancer. Insoluble fiber in the diet speeds up the movement of the stools through the gastrointestinal tract. The faster food travels through the digestive tract, the less time there is for potential cancer-causing substances to work. Therefore, diets high in insoluble fiber help prevent the accumulation of toxic substances that cause cancer of the colon. New studies released in 2003 seemed to confirm these findings. Because fiber reduces fat absorption in the digestive tract, it also may prevent breast cancer .

A diet low in fat also promotes good health and prevents many diseases. Low-fat diets can help treat or control the following conditions:

  • Obesity. High fat consumption often leads to excess caloric and fat intake, which increases body fat.
  • Coronary artery disease. High consumption of saturated fats is associated with coronary artery disease.
  • Diabetes. People who are overweight tend to develop or worsen existing diabetic conditions due to decreased insulin sensitivity.
  • Breast cancer. A high dietary consumption of fat is associated with an increased risk of breast cancer.

Description

The four basic food groups, as outlined by the United States Department of Agriculture (USDA) are:

  • dairy products (such as milk and cheese)
  • meat and eggs (such as fish, poultry, pork, beef, and eggs)
  • grains (such as bread, cereals, rice, and pasta)
  • fruits and vegetables

The USDA recommendation for adults is that consumption of meat, eggs, and dairy products should not exceed 20% of total daily caloric intake. The rest (80%) should be devoted to vegetables, fruits, and grains. For children age two or older, 55% of their caloric intake should be in the form of carbohydrates, 30% from fat, and 15% from proteins. In addition, saturated fat intake should not exceed 10% of total caloric intake. This low-fat, highfiber diet is believed to promote health and help prevent many diseases, including heart disease, obesity, and cancer.

Allergenic and highly processed foods should be avoided. Highly processed foods do not contain significant amounts of essential trace minerals. Furthermore, they contain lots of fat and sugar as well as preservatives, artificial sweeteners and other additives. High consumption of these foods causes buildup of these unwanted chemicals in the body and should be avoided. Food allergy causes a variety of symptoms including food cravings, weight gain, bloating, and water retention. It also may worsen chronic inflammatory conditions such as arthritis.

Preparations

An enormous body of research exists in the field of nutrition. Mainstream Western medical practitioners point to studies that show that a balanced diet, based on the USDA Food Guide Pyramid, provides all of the necessary nutrients. However, the USDA is working to revise the pyramid for the first time in a decade. Other pyramids are suggested by various research agencies, many of which emphasize different nutrition areas. A Harvard University researcher emphasizes whole grains and plant oils over meat, dairy and refined carbohydrates. Some nutritionists believe that the USDA will modify the Food Pyramid to reflect similar modifications. The basic pyramid will likely not change, but explanations about the types of fats, grains and carbohydrates that are best to choose are likely.

In the first revision of the Food Guide Pyramid in 2003, the USDA proposed new patterns about how much Americans eat. Calorie recommendations and vitamin intake will be based on a person's age, sex, and activity level. The complete revision was proposed for final publishing in the winter of 2005. As of early 2004, the Food Guide Pyramid recommends the following daily servings in six categories:

  • grains: Six or more servings
  • vegetables: Five servings
  • fruits: Two to four servings
  • meat: Two to three servings
  • dairy: Two to three servings
  • fats and oils: Use sparingly

A new food guide pyramid for various vegetarian diets has been released by the American Dietetic Association (ADA). The guide helps vegetarians obtain the vitamins and minerals they need from whole grains, vegetables, fruits, legumes, nuts and other protein-rich foods.

Precautions

Individuals should not change their diets without the advice of nutritional experts or health care professionals. Certain individuals, especially children, pregnant and lactating women, and chronically ill patients should only change their diets under professional supervision.

Side effects

It is best to obtain vitamins and minerals through food sources. Excessive intake of vitamins and mineral supplements can cause serious physiological problems. 2001 guidelines to help nutritionists counsel cancer patients in use of complementary and alternative medicine reported that 73% of cancer patients used these therapies in addition to their allopathic treatment. Of those, only about 38% discussed the alternative therapies with their physicians. Patients using dietary supplements should document their use, discuss them with their doctor or nutritionist, and watch standard cautions like possible interactions with prescribed drugs, cumulative effects of several supplements containing the same vitamin or mineral, and to stop taking the supplements if adverse reactions occur.

The following is a list of possible side effects resulting from excessive doses of vitamins and minerals:

  • vitamin A: Birth defects, irreversible bone and liver damage
  • vitamin B1: Deficiencies in B2 and B6
  • vitamin B6: Damage to the nervous system
  • vitamin C: Effects on the absorption of copper; diarrhea
  • vitamin D: Hypercalcemia (abnormally high concentration of calcium in the blood)
  • phosphorus: affects the absorption of calcium
  • zinc: affects absorption of copper and iron; suppression of the immune system

Research & general acceptance

Due to a large volume of scientific evidence demonstrating the benefits of the low-fat, high-fiber diet in disease prevention and treatment, this diet has been accepted and advocated by both complementary and allopathic practitioners.

Resources

BOOKS

Bruce, Debra Fulghum, and Harris H. McIlwain. The Unofficial Guide to Alternative Medicine. New York: Macmillan, 1998.

Cassileth, Barrie R. The Alternative Medicine Handbook. New York: W.W. Norton, 1998.

Credit, Larry P., Sharon G. Hartunian, and Margaret J. Nowak. Your Guide to Complementary Medicine. Garden City Park, New York: Avery Publishing Group, 1998.

U.S. Preventive Services Task Force Guidelines. "Counseling to Promote a Healthy Diet." Guide to Clinical Preventive Services, 2nd edition. http://cpmcnet.columbia.edu/texts/gcps/gcps0066.html.

Winick, Myron. The Fiber Prescription. New York: Random House, Inc., 1992.

PERIODICALS

Halbert, Steven C. "Diet and Nutrition in Primary Care: From Antioxidants to Zinc." Primary Care: Clinics in Office Practice (December 1997): 825-843.

Mangels, Reed. "New Vegetarian Food Guide." Vegetarian Journal (JulyAugust 2003): 12.

Shapiro, Alice C., et al. "Guidelines for Responsible Nutrition Counseling on Complementary and Alternative Medicine." Nutrition Today (November-December 2001): 291 -297.

Sugarman, Carole. "USDA Proposes New Intake Patterns for Food Guide Pyramid." Food Chemical News (Sept. 15, 2003): 1.

Turner, Lisa. "Good 'n Plenty." Vegetarian Times (February 1999):48

"Two Studies Find High-fiber Diet Lowers Colon Cancer Risk." Ca (JulyAugust 2003): 201.

VanBeusekom, Mary. "Converted Food Pyramid: the USDA Revises its Decade-old Food Guidelines." MPLS-St. Paul Magazine (August 2003): 6064.

Vickers, Andrew, and Catherine Zollman. "Unconventional approaches to nutritional medicine." British Medical Journal (November 27, 1999): 1419.

ORGANIZATIONS

American Association of Nutritional Consultants. 810 S. Buffalo Street, Warsaw, IN 46580. (888) 828-2262.

American Dietetic Association. 216 W.Jackson boulevard, Suite 800, Chicago, IL 60606-6995. (800) 366-1655. http://www.eatright.org/.

Teresa G. Odle

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Odle, Teresa. "Nutrition." Gale Encyclopedia of Alternative Medicine. 2005. Encyclopedia.com. 27 Sep. 2016 <http://www.encyclopedia.com>.

Odle, Teresa. "Nutrition." Gale Encyclopedia of Alternative Medicine. 2005. Encyclopedia.com. (September 27, 2016). http://www.encyclopedia.com/doc/1G2-3435100571.html

Odle, Teresa. "Nutrition." Gale Encyclopedia of Alternative Medicine. 2005. Retrieved September 27, 2016 from Encyclopedia.com: http://www.encyclopedia.com/doc/1G2-3435100571.html

Nutrition

Nutrition

Definition

Good nutrition can help prevent disease and promote health. There are six categories of nutrients that the body needs to acquire from food: protein, carbohydrates, fat, fibers, vitamins and minerals, and water.

Proteins

Protein supplies amino acids to build and maintain healthy body tissue. There are 20 amino acids considered essential because the body must have all of them in the right amounts to function properly. Twelve of these are manufactured in the body but the other eight amino acids must be provided by the diet. Foods from animal sources such as milk or eggs often contain all these essential amino acids while a variety of plant products must be taken together to provide all these necessary protein components.

Fat

Fat supplies energy and transports nutrients. There are two families of fatty acids considered essential for the body: the omega-3 and omega-6 fatty acids. Essential fatty acids are required by the body to function normally. They can be obtained from canola oil, flaxseed oil, cold-water fish, or fish oil, all of which contain omega-3 fatty acids, and primrose or black currant seed oil, which contains omega-6 fatty acids. The American diet often contains an excess of omega-6 fatty acids and insufficient amounts of omega-3 fats. Increased consumption of omega-3 oils is recommended to help reduce risk of cardiovascular diseases and cancer and alleviate symptoms of rheumatoid arthritis, premenstrual syndrome, dermatitis, and inflammatory bowel disease.

Carbohydrates

Carbohydrates are the body's main source of energy and should be the major part of total daily intake. There are two types of carbohydrates: simple carbohydrates (such as sugar or honey) or complex carbohydrates (such as grains, beans, peas, or potatoes). Complex carbohydrates are preferred because these foods are more nutritious yet have fewer calories per gram compared to fat and cause fewer problems with overeating than fat or sugar. Complex carbohydrates also are preferred over simple carbohydrates by diabetics because they allow better blood glucose control.

Fiber

Fiber is the material that gives plants texture and support. Although it is primarily made up of carbohydrates, it does not have a lot of calories and is usually not broken down by the body for energy. Dietary fiber is found in plant foods such as fruits, vegetables, legumes, nuts, and whole grains.

There are two types of fiber: soluble and insoluble. Insoluble fiber, as the name implies, does not dissolve in water because it contains high amount of cellulose. Insoluble fiber can be found in the bran of grains, the pulp of fruit and the skin of vegetables. Soluble fiber is the type of fiber that dissolves in water. It can be found in a variety of fruits and vegetables such as apples, oatmeal and oat bran, rye flour, and dried beans.

Although they share some common characteristics such as being partially digested in the stomach and intestines and have few calories, each type of fiber has its own specific health benefits. Insoluble fiber speeds up the transit of foods through the digestive system and adds bulk to the stools, therefore, it is the type of fiber that helps treat constipation or diarrhea and prevents colon cancer. On the other hand, only soluble fiber can lower blood cholesterol levels. This type of fiber works by attaching itself to the cholesterol so that it can be eliminated from the body. This prevents cholesterol from recirculating and being reabsorbed into the bloodstream. In 2003, the World Health Organization released a new report specifically outlining the link of a healthy diet rich in high-fiber plant foods to preventing cancer.

Vitamins and minerals

Vitamins are organic substances present in food and required by the body in a small amount for regulation of metabolism and maintenance of normal growth and functioning. The most commonly known vitamins are A, B1 (thiamine), B2 (riboflavin), B3 (niacin), B5 (pantothenic acid), B6 (pyridoxine), B7 (biotin), B9 (folic acid), B12 (cobalamin), C (ascorbic acid), D, E, and K. The B and C vitamins are watersoluble, excess amounts of which are excreted in the urine. The A, D, E, and K vitamins are fat-soluble and will be stored in the body fat.

Minerals are vital to our existence because they are the building blocks that make up muscles, tissues, and bones. They also are important components of many life-supporting systems, such as hormones, oxygen transport, and enzyme systems.

There are two kinds of minerals: the major (or macro) minerals and the trace minerals. Major minerals are the minerals that the body needs in large amounts. The following minerals are classified as major: calcium, phosphorus, magnesium, sodium, potassium, sulfur, and chloride. They are needed to build muscles, blood, nerve cells, teeth, and bones. They also are essential electrolytes that the body requires to regulate blood volume and acid-base balance.

Unlike the major minerals, trace minerals are needed only in tiny amounts. Even though they can be found in the body in exceedingly small amounts, they are also very important to the human body. These minerals participate in most chemical reactions in the body. They also are needed to manufacture important hormones. The following are classified as trace minerals: iron, zinc, iodine, copper, manganese, fluoride, chromium, selenium, molybdenum, and boron.

Many vitamins (such as vitamins A, C, and E) and minerals (such as zinc, copper, selenium, or manganese) act as antioxidants. They protect the body against the damaging effects of free radicals. They scavenge or mop up these highly reactive radicals and change them into inactive, less harmful compounds. In so doing, these essential nutrients help prevent cancer and many other degenerative diseases, such as premature aging, heart disease, autoimmune diseases, arthritis, cataracts, Alzheimer's disease, and diabetes mellitus.

Water

Water helps to regulate body temperature, transports nutrients to cells, and rids the body of waste materials.

Origins

Unlike plants, human beings cannot manufacture most of the nutrients that they need to function. They must eat plants and/or other animals. Although nutritional therapy came to the forefront of the public's awareness in the late twentieth century, the notion that food affects health is not new. John Harvey Kellogg was an early health-food pioneer and an advocate of a high-fiber diet. An avowed vegetarian, he believed that meat products were particularly detrimental to the colon. In the 1870s, Kellogg founded the Battle Creek Sanitarium, where he developed a diet based on nut and vegetable products.

Purpose

Good nutrition helps individuals achieve general health and well-being. In addition, dietary modifications might be prescribed for a variety of complaints including allergies, anemia, arthritis, colds, depressions, fatigue, gastrointestinal disorders, high or low blood pressure, insomnia, headaches, obesity, pregnancy, premenstrual syndrome (PMS), respiratory conditions, and stress.

Nutritional therapy may also be involved as a complement to the allopathic treatments of cancer, diabetes, and Parkinson's disease. Other specific dietary measures include the elimination of food additives for attention deficit hyperactivity disorder (ADHD), gluten-free diets for schizophrenia, and dairy-free for chronic respiratory diseases.

A high-fiber diet helps prevent or treat the following health conditions:

  • High cholesterol levels. Fiber effectively lowers blood cholesterol levels. It appears that soluble fiber binds to cholesterol and moves it down the digestive tract so that it can be excreted from the body. This prevents the cholesterol from being reabsorbed into the bloodstream.
  • Constipation. A high-fiber diet is the preferred nondrug treatment for constipation. Fiber in the diet adds more bulk to the stools, making them softer and shortening the time foods stay in the digestive tract.
  • Hemorrhoids. Fiber in the diet adds more bulk and softens the stool, thus, reducing painful hemorrhoidal symptoms.
  • Diabetes. Soluble fiber in the diet slows down the rise of blood sugar levels following a meal and helps control diabetes.
  • Obesity. Dietary fiber makes a person feel full faster.
  • Cancer. Insoluble fiber in the diet speeds up the movement of the stools through the gastrointestinal tract. The faster food travels through the digestive tract, the less time there is for potential cancer-causing substances to work. Therefore, diets high in insoluble fiber help prevent the accumulation of toxic substances that cause cancer of the colon. Because fiber reduces fat absorption in the digestive tract, it also may prevent breast cancer.

A diet low in fat also promotes good health and prevents many diseases. Low-fat diets can help treat or control the following conditions:

  • Obesity. High fat consumption often leads to excess caloric and fat intake, which increases body fat.
  • Coronary artery disease. High consumption of saturated fats is associated with coronary artery disease.
  • Diabetes. People who are overweight tend to develop or worsen existing diabetic conditions due to decreased insulin sensitivity.
  • Breast cancer. A high dietary consumption of fat is associated with an increased risk of breast cancer.

Description

The four basic food groups, as outlined by the United States Department of Agriculture (USDA) are:

  • dairy products (such as milk and cheese)
  • meat and eggs (such as fish, poultry, pork, beef, and eggs)
  • grains (such as bread cereals, rice, and pasta)
  • fruits and vegetables

The USDA recommendation for adults is that consumption of meat, eggs, and dairy products should not exceed 20% of total daily caloric intake. The rest (80%) should be devoted to vegetables, fruits, and grains. For children age two or older, 55% of their caloric intake should be in the form of carbohydrates, 30% from fat, and 15% from proteins. In addition, saturated fat intake should not exceed 10% of total caloric intake. This low-fat, high-fiber diet is believed to promote health and help prevent many diseases, including heart disease, obesity, and cancer.

Allergenic and highly processed foods should be avoided. Highly processed foods do not contain significant amounts of essential trace minerals. Furthermore, they contain lots of fat and sugar as well as preservatives, artificial sweeteners and other additives. High consumption of these foods causes build up of unwanted chemicals in the body and should be avoided. Food allergies causes a variety of symptoms including food cravings, weight gain, bloating, and water retention. They also may worsen chronic inflammatory conditions such as arthritis.

Preparations

An enormous body of research exists in the field of nutrition. Mainstream Western medical practitioners point to studies that show that a balanced diet, based on the USDA Food Guide Pyramid, provides all of the necessary nutrients.

In 2004, the USDA was working on a revision of the Food Guide Pyramid to reflect changes in American lifestyle habits. The new eating guide was due for release in January 2005. The World Health Organization (WHO) also was weighing in on the obesity and nutrition issue, even struggling with objections from member nations that supply goods such as sugar, to endorse a global strategy in spring 2004 on diet, physical activity and health.

The Food Guide Pyramid recommends the following daily servings in six categories:

  • grains: six or more servings
  • vegetables: five servings
  • fruits: two to four servings
  • meat: two to three servings
  • dairy: two to three servings
  • fats and oils: use sparingly

Precautions

Individuals should not change their diets without the advice of nutritional experts or health care professionals. Certain individuals, especially children, pregnant and lactating women, and chronically ill patients, only should change their diets under professional supervision.

Side effects

It is best to obtain vitamins and minerals through food sources. Excessive intake of vitamins and mineral supplements can cause serious health problems. Likewise, eating too much of one type of food, as can happen with fad diets, can be harmful. The key to nutrition is moderation. If a person feels they are short on iron, for example, he or she should not go too far to the extreme in getting more iron through diet and supplements. A 2003 report said that too much stored iron in the body has possibly been linked with heart disease, cancer and diabetes.

The following is a list of possible side effects resulting from excessive doses of vitamins and minerals:

  • vitamin A: birth defects, irreversible bone and liver damage
  • vitamin B1: deficiencies in B2 and B6
  • vitamin B6: damage to the nervous system
  • vitamin C: affects the absorption of copper; diarrhea
  • vitamin D: hypercalcemia (abnormally high concentration of calcium in the blood)
  • phosphorus: affects the absorption of calcium
  • zinc: affects absorption of copper and iron; suppresses the immune system

Research and general acceptance

Due to a large volume of scientific evidence demonstrating the benefits of the low-fat, high-fiber diet in disease prevention and treatment, these recommendations have been accepted and advocated by both complementary and allopathic practitioners.

Resources

BOOKS

U.S. Preventive Services Task Force Guidelines. "Counseling to Promote a Healthy Diet." Guide to Clinical Preventive Services. 2nd ed. http://cpmcnet.-columbia.edu/texts/gcps/gcps0066.html.

PERIODICALS

Clapp, Stephen. "World Health Assembly Adopts Global Anti-obesity Strategy." Food Chemical News May 31, 2004: 26.

Halbert, Steven C. "Diet and Nutrtion in Primary Care: From Antioxidants to Zinc." Primary Care: Clinics in Office Practice December 1997: 825-843.

Mangels, Reed. "How Can You Avoid Having Too Much Iron?" Vegetarian Journal March-April 2003: 17.

Turner, Lisa. "Good 'n Plenty." Vegetarian Times February 1999: 48.

"U.N. Report Supports Key Role for Diet, Activity in Cancer Prevention." Cancer Weekly March 25, 2003: 154.

Vickers, Andrew, and Catherine Zollman. "Unconventional approaches to nutritional medicine." British Medical Journal November 27, 1999: 1419.

ORGANIZATIONS

American Association of Nutritional Consultants. 810 S. Buffalo Street, Warsaw, IN 46580. (888) 828-2262.

American Dietetic Association. 216 W. Jackson boulevard, Suite 800, Chicago, IL 60606-6995. (800) 366-1655. http://www.eatright.org.

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Tran, Mai; Odle, Teresa. "Nutrition." Gale Encyclopedia of Medicine, 3rd ed.. 2006. Encyclopedia.com. 27 Sep. 2016 <http://www.encyclopedia.com>.

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Nutrition

Nutrition

The term nutrition refers to the sum total of all the processes by which an organism takes in and makes use of the foods it needs to survive, grow, move, and develop. The word nutrition is also used to refer to the study of the substances an organism needs in order to survive. Those substances are known as nutrients.

Some organisms, such as plants, require nothing other than a supply of light, water, and simple chemicals in order to thrive. Such organisms are known as autotrophs, or self nourishers. Autotrophs build all the molecules they need and capture energy in the process. A few nonplant autotrophic organisms live in the deep oceans near hydrothermal vents (cracks in the ocean floor caused by volcanic activity). These organisms are able to build their own nutrients without using sunlight from sulfur compounds found around the vents.

While green plants get the energy they need directly from sunlight, animals must get the energy they need for life functions from plants.

Nutrients

The major classes of nutrients are carbohydrates, proteins, lipids (or fats), vitamins, and minerals. Animals also need other substances, such as water, fiber, and oxygen, in order to survive. But these substances are not usually regarded as nutrients.

Proteins. Proteins are large molecules built from different combinations of simpler compounds known as amino acids. Human proteins consist of 20 different amino acids. Of these 20 amino acids, the human body is able to manufacture 12 from the foods we eat. The body is unable, however, to make the remaining 8 amino acids it needs for protein production. These 8 amino acids are said to be essential because it is essential that they be included in the human diet.

Proteins that contain all of the essential amino acids are said to be complete proteins. Good sources of complete proteins include fish, meat, poultry, eggs, milk, and cheese. Proteins lacking one or more essential amino acids are incomplete proteins. Peas, beans, lentils, nuts, and cereal grains are sources of incomplete proteins. Anyone whose diet consists primarily of corn and corn products would be at risk for developing health problems because corn lacks two essential amino acids: lysine and tryptophan.

The function of proteins is to promote normal growth, repair damaged tissue, make enzymes, and contribute to the body's immune system.

Carbohydrates. The carbohydrates include sugar and starchy foods, such as those found in cereal grains, potatoes, rice, and fruits. Their primary function in the body is to supply energy. When a person takes in more carbohydrates than his or her body can use, the excess is converted to a compound known as glycogen. Glycogen is stored in liver and muscle tissue and can be used as a source of energy by the body at future times.

Words to Know

Amino acid: A chemical compound used in the construction of proteins.

Autotroph: An organism that can build all the food and produce all the energy it needs with its own resources.

Carbohydrate: A chemical compound, such as sugar or starch, used by animals as a source of energy.

Complete protein: A protein that contains all essential amino acids.

Edema: An abnormal collection of fluids in body tissues.

Essential amino acids: Amino acids that cannot be produced by an animal, such as a human, and that must, therefore, be obtained from that animal's regular diet.

Food pyramid: A diagram developed by the U.S. Department of Agriculture that illustrates the relative amounts of various nutrients needed for normal human growth and development.

Glycogen: A chemical compound in which unused carbohydrates are stored in an animal's body.

Incomplete protein: A protein that lacks one or more essential amino acids.

Indigestible fiber: Fiber that has no nutritional value, but that aids in the normal functioning of the digestive system.

Lipid: A chemical compound used as a source of energy, to provide insulation, and to protect organs in an animal body; a fat or oil

Micronutrient: A nutrient needed in only small amounts by an organism.

Mineral: An inorganic substance found in nature.

Night blindness: Inability to see at night due to a vitamin A deficiency.

Nutrient: A substance needed by an organism in order for it to survive, grow, and develop.

Nutrient deficiency disease: A disease that develops when an organism receives less of a nutrient than it needs to remain healthy.

Protein: A complex chemical compound that consists of many amino acids attached to each other that are essential to the structure and functioning of all living cells.

Vitamin: A complex organic compound found naturally in plants and animals that the body needs in small amounts for normal growth and activity.

Lipids. The term lipid refers to both fats and oils. Lipids serve a number of functions in the human body. Like carbohydrates, they are used to supply energy. In fact, a gram of lipid produces about three times as much energy as a gram of carbohydrate when it is metabolized (burned). The release of energy from lipids takes place much more slowly than it does from carbohydrates, however.

Lipids also protect the body's organs from shock and damage and provide insulation for the body.

Vitamins and minerals. Vitamins and minerals are substances needed by the body in only very small amounts. They are also substances that the body cannot produce itself. Thus, they must be included in a person's diet on a regular basis. Vitamins and minerals are sometimes known as micronutrients because they are needed in such small quantities.

An example of a vitamin is the compound known as vitamin A. Vitamin A is required in order for a person to be able to see well at night. An absence of the vitamin can result in a condition known as night-blindness as well as in dryness of the skin. Vitamin A occurs naturally in foods such as green and yellow vegetables, eggs, fruits, and liver.

An example of a mineral is calcium, an element needed to build strong bones and teeth. Calcium is also involved in the normal function of nerve and muscle activity. Good sources of calcium include milk and eggs.

The food pyramid

The food pyramid is a diagram developed by the U.S. Department of Agriculture (USDA) to illustrate the components needed in a healthy diet. The bottom level of the pyramid contains the cereal foods, such as breads, pastas, and rice. This group of foods consists primarily of carbohydrates and is, therefore, a major source of energy. The USDA recommends 6 to 11 servings per day from this group. A serving consists of 30 to 60 grams (1 to 2 ounces) of the food. The exact number of servings depends on the age, gender, weight, and degree of activity for any given person.

The second level of the food pyramid consists of fruits and vegetables. These foods are especially important in supplying vitamins and minerals. A second benefit derived from this group comes from indigestible

fiber. Indigestible fiber has been shown to improve the functioning and health of the large intestine. Five to nine servings a day are suggested from this group.

The third level of the pyramid consists of proteins in the form of meats, eggs, beans, nuts, and milk products. This level is smaller than the first and second levels to emphasize that the percentage of these foods should be smaller in comparison to a person's total food intake.

The tip of the pyramid contains the lipids. The small space allotted to the lipids emphasizes that fats and oils should be consumed in small quantities for optimum health.

Nutrient deficiency diseases

The lack of any nutrient can lead to some kind of disease. For example, people who do not have enough protein in their diets may develop a condition known as kwashiorkor. Kwashiorkor (pronounced kwah-shee-OR-kor) is characterized by apathy (lack of interest), muscular wasting, and edema (collection of water in the body). Both the hair and skin lose their pigmentation, and the skin becomes scaly. Diarrhea and anemia (a blood disorder characterized by tiredness) are common, and permanent blindness may result from the condition. Experts estimate that millions of infants die every year worldwide from kwashiorkor.

Rickets is an example of a vitamin deficiency disorder. Rickets develops when a person does not receive enough vitamin D in his or her diet. As a result, the person's bones do not develop properly. His or her legs become bowed by the weight of the body, and wrists and ankles become thickened. Teeth are also badly affected and may take much longer than normal to mature, if they do so at all. Rickets is common among dwellers in slums, where sunlight is not available. (Sunlight causes the natural formation of vitamin D in the skin.) Rickets is no longer a threat in many nations because milk and infant formulas have vitamin D added to them artificially.

[See also Amino acid; Carbohydrate; Lipids; Malnutrition; Protein; Vitamin ]

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nutrition

nutrition, study of the materials that nourish an organism and of the manner in which the separate components are used for maintenance, repair, growth, and reproduction. Nutrition is achieved in various ways by different forms of life. Plants that contain the green pigment chlorophyll can synthesize their food from inorganic substances in the process called photosynthesis. Organisms such as plants that can thus manufacture complex organic compounds from simple inorganic nutrients are termed autotrophic. Organisms that must obtain "prefabricated" organic compounds from their environment are heterotrophic, and these include the fungi, some other plants, and animals. Heterotrophic plants may be saprophytic (obtaining nutrients from dead organisms) or parasitic (obtaining nutrients from living organisms while living on or in them). Heterotrophic animals may be parasites, herbivores (plant eaters), carnivores (meat eaters), or omnivores (obtaining nutrition from both plants and animals).

Human Nutrition

Humans require food substances to supply the components necessary to build tissues, to repair tissues as they wear out and die, to keep the body in good working condition, and to supply fuel for energy. For good nutrition a person should eat a well-balanced diet, that is, one that provides an adequate amount of each of the classes of nutrients each day, furnishing at the same time an adequate but not excessive number of calories for the body's energy needs. Children require relatively larger amounts of nutrients and calories because of their rapid growth. The foods required for proper nutrition fall roughly into three major groups: proteins, carbohydrates, and fats; vitamins, minerals, and water are also important.

Proteins

Protein in the diet provides amino acids for forming body proteins, including the structural proteins for building and repairing tissues, and the enzymes for carrying out the metabolic processes. In addition, protein may be used as a source of energy when the preferred fat and carbohydrate supply runs low. A body that is in the process of building itself (such as that of a growing child or an adult recovering from illness) will need a greater proportion of protein to weight than one that is fully grown and utilizes protein merely for repair of worn-out tissues. The average adult requires 1 gram of protein per kilogram of body weight per day; children may require two to three times this amount. Human proteins consist of up to 22 different amino acids, of which 9 (called essential amino acids) must be supplied by food protein; the other 13 are synthesized by human cells. Complete protein sources—those foods containing all 22 amino acids—include animal products such as meat, eggs, cheese, and milk. Incomplete protein sources, such as vegetables, beans, and grains, may be combined to create complete proteins.

Carbohydrates

Carbohydrates (starches and sugars) provide a readily available energy source. Surplus carbohydrates are also converted by the body to glycogen and fat, the storage forms of calories for energy, and to some of the amino acids used in protein synthesis. Most health professionals recommend that carbohydrates comprise 50% to 60% of the dietary calories, of which most (c.80% of all carbohydrates eaten) should be complex carbohydrates, such as cereals and vegetables. Complex carbohydrates are preferred because the fast-acting simple carbohydrates, such as honey and sugar, are difficult for the body (especially the pancreas) to handle in large doses. Simple carbohydrates also lack the vitamins, minerals, proteins, and fiber that generally accompany foods rich in complex carbohydrates. Cereals, fruits, vegetables, legumes, and pasta are good sources of complex carbohydrates.

Fats

Fats (see fats and oils) in the diet provide a concentrated source of energy; 1 gram of fat supplies about 9 calories as opposed to only 4 calories per gram of carbohydrates and protein. Fats in the body, in addition to acting as a source of stored energy, supply physical protection and insulation for tissues and form important portions of cell membrane structure. Fats also aid in the absorption of the fat-soluble vitamins (vitamins A, D, E, and K) from the intestine. Milk, butter, meat, and oils are important sources of fat.

Vitamins, Minerals, and Water

To keep the body functioning properly it is necessary to have, in addition to the basic foods, a sufficient intake of accessory substances such as vitamins, minerals (see mineral, dietary), and enough water to carry nutrients to the tissues and waste products away from them. A minimum of about 2 liters of liquid per day are recommended for the average adult. Vitamins function as coenzymes in important body processes, with the exception of vitamin D, which is synthesized upon exposure to sunlight. A large variety of minerals are required, some in trace amounts and others, such as calcium and iron, in relatively large amounts. Milk, cheese, and dark, leafy green vegetables are excellent sources of calcium; liver, meat, and egg yolks are good sources of iron. Minerals are vital to the development of teeth and bones (calcium, phosphorus, and fluoride) and to the functioning of a number of the body's metabolic systems. Iron is a necessary part of hemoglobin in the blood; various metals are required in many enzymes; sodium and potassium are essential to maintenance of fluid balance and functioning of the nervous system; magnesium is needed for the normal functioning of nerves and muscles; and iodine is required for thyroid hormone. The usefulness of vitamin and mineral supplements for a person of good health who eats a well-balanced diet continues to provoke debate among health experts.

Importance of Good Nutrition

Good nutrition is reflected not only in the growth and function of the body but also in its appearance. The eyes, skin, hair, and teeth indicate whether body nourishment is good or poor. A poorly nourished child will fail to grow properly; a poorly nourished adult will have a decreased resistance to infection and disease. A diet deficient in proteins causes a disease called kwashiorkor in children; a diet deficient in both protein and calories results in marasmus, with lethargy, abdominal enlargement, and wasting—the classical malnutrition syndrome. Poor nutrition may result from excesses in the diet as well as deficiencies; excess of certain vitamins or minerals can produce potentially lethal disease states, and excess of carbohydrates or fat can result in obesity.

The Food Guide Pyramid

The U.S. Dept. of Agriculture (USDA) illustrates a well-balanced diet with the Food Guide Pyramid (1992), which emphasizes the need to eat less fat and proportionally more complex carbohydrates. At the base of the pyramid is the grains group, which should be eaten in the largest quantity (6–11 servings per day). Just above are the two groups fruits (2–4 servings) and vegetables (3–5 servings). Near the top are the meat products (2–3 servings) and dairy products (2–3 servings). At the apex are the fats, oils, and sweets, which are not considered a food group and should be consumed sparingly. See also food pyramid.

Specialized Diets

Specialized diets are useful in the treatment of certain disease states; the most common is a low-calorie diet to produce weight loss in obese persons. A diet low in phenylalanine is used to treat phenylketonuria. A diet low in cholesterol and saturated fats seems to be useful in the treatment and prevention of heart disease. Elimination of certain foods from the diet may be necessary to control allergies in some individuals. In all cases, however, specialized diets must provide all classes of essential nutrients in adequate amounts to maintain health in adults and support growth in children.

Bibliography

See J. Brody, Jane Brody's Nutrition Book (1981); S. Gershoff, The Tufts University Guide to Total Nutrition (1990); J. Mayer, Jean Mayer's Diet and Nutrition Guide (1990).

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Nutrition

Nutrition

BIBLIOGRAPHY

Nutrition is a vital physiologic process necessary for the development and maintenance of the human body, its organs, and its physiological processes. In order to maintain good health, individuals require daily intake of protein, fat, and carbohydratesnutrients that provide energy, vitamins, minerals, and water. Nutrition provides necessary nutrients that are not produced by the body. The daily requirements of these nutrients vary depending on individuals age, sex, and physiologic state (that is, pregnancy).

In the United States dietary guidelines are updated every five years and are the basis for the Food Guide Pyramid. These guidelines are issued by the U.S. Department of Agriculture (USDA) and the U.S. Department of Health and Human Services (HHS). The Food Guide Pyramid groups foods into major categories (fruit, vegetable, dairy, grain, meat, and bean) and recommends serving sizes and the number of servings needed to achieve balanced nutrition and health. In 2005, to address the dramatic rise in obesity, the USDA modified the Food Guide Pyramid to emphasize lower energy intake and more physical activity and provide an individualized approach. The USDA promotes nutrition based on the fact that certain dietary patterns may place individuals at risk of chronic diseases, such as cardiovascular disease, diabetes, and cancer. Diets rich in saturated fat and low in fruits and vegetables are associated with heart disease, cancer, and diabetes, while diets rich in fruits and vegetables may protect individuals from these conditions.

The balance between energy intake and energy expenditure determines weight maintenance or weight gain and loss. When regular energy intake is greater than the expenditure, the body stores the surplus of energy as extra body fat or adipose tissue. Energy expenditure is a result of the basal metabolic rate, the thermic effect of food (energy spent in processing food), and the energy spent in physical activity. The contribution of physical activity to energy balance is small compared to food intake. Energy intake and dietary patterns are influenced by hormonal mechanisms and psychosocial factors. People eat in response to hunger signals that the body creates, such as changes in blood glucose levels. Hunger can also be experienced in response to sensory cues, such as the smell or sight of favorite foods.

Satiety is regulated by a complex hormonal signaling system with input from proteins secreted by the brain, the gastrointestinal tract, and the liver. In the brain the hypothalamus secretes small proteins called neuropeptides. The neuropeptides inhibit food intake after receiving input from hormones and proteins synthesized in the stomach and intestines. Ghrelin, which is synthesized predominantly by the stomach, stimulates feeding. In the fasting state ghrelin levels are high, and levels fall after eating. The intestine releases cholecystokinin (CCK) after a meal, which stimulates gut motility, the contractions of gastrointestinal muscles that enable food to move along the digestive tract and ensure absorption of nutrients and inhibits food intake by signals to the brain. Other organs and hormones are also involved in the regulation of food intake and satiety. After a meal, the pancreas secretes insulin, which in turn signals the brain to inhibit feeding. Leptin is a hormone synthesized in adipose (fat) cells, and its secretion is regulated by the obese (ob) gene. Leptin levels are low during starvation and high when nutrients are plentiful and in obesity. High levels of leptin signal the brain to reduce appetite. In obesity people are resistant to the effects of leptin. The hormone adiponectin is secreted by adipose cells, and its secretion is stimulated by food restriction. Adiponectin is also a factor that increases energy expenditure, and low levels may contribute to the development of obesity.

The body seems to tolerate positive energy balance, that is, when energy intake is higher than expenditure. The mechanisms described above strongly defend from weight loss but not from weight gain because of an evolutionary process that favored intake of nutrients when food was easily accessible and in preparation of times when food was scarce. This evolutionary perspective can explain in part the obesity epidemic that emerged during the last decades of the twentieth century when, in developed countries, there was abundance of food without periods of scarcity.

Nutrition is not only influenced by biological factors. Environment, culture, and social factors also play important roles in nutrition. The environment determines the type and quality of foods accessible to individuals and communities. A diet rich in refined sugars, carbohydrates, and fat is related to increased availability of fast foods, sugared beverages, and low-nutritional value snacks and decreased access to produce (fruits and vegetables). A positive energy balance in turn is caused by increasing calorie intake, especially when reinforced with a sedentary lifestyle. Social factors, such as low income and low socioeconomic status, are associated with less healthy dietary patterns with higher saturated fat intake and lower intake of fruits and vegetables possibly due to the facts that low-income individuals are more likely to live in communities with less access to healthy foods and that healthier food items are proportionally more expensive that unhealthy ones. Industrialized societies eat a diet rich in meat and saturated fat and lower in fiber compared to agrarian societies, who consume more fruits, vegetables, and grains. Research indicates that immigration changes dietary patterns of individuals, who over time adopt the diet of their host country.

In people with excess weight, a diet restricting calories but maintaining balanced nutrient composition can achieve healthy weight loss and reduce the risk of diabetes and cardiovascular disease, which are conditions associated with obesity. However, when the calorie restriction is severe and the diet does not allow for sufficient amounts of essential nutrients, dieting can lead to metabolic and heart problems and even death. The psychological factors that are associated with nutrition are best exemplified by obesity and eating disorders. Obese individuals frequently have low self-esteem and depression. Whether these are causes or consequences of obesity is still under debate. Some individuals may increase their food intake in response to feelings of stress, loneliness, and anxiety, which place them at risk of overweight and obesity. Eating disorders include anorexia, characterized by being severely underweight from excessive food intake restriction, and bulimia, characterized by purging. Either disorder may also have periods of binge eating. Eating disorders, especially anorexia, are associated with body image dissatisfaction, depression, and low self-esteem.

SEE ALSO Body Image; Depression, Psychological; Disease; Food; Malnutrition; Obesity; Overeating; Self-Esteem; Stunted Growth; Undereating

BIBLIOGRAPHY

Geissler, Catherine, and Hilary Powers. 2005. Human Nutrition. Edinburgh: Elsevier Churchill Livingstone.

Shils, Maurice E., James A. Olson, Moshe Shike, et al., eds. 2005. Modern Nutrition in Health and Disease. Baltimore, MD: Lippincott Williams and Wilkins.

Temple, Norman J., Ted Wilson, and David R. Jacobs. 2006. Nutritional Health: Strategies for Disease Prevention. Totowa, NJ: Humana.

U.S. Department of Agriculture. 2005. My Pyramid: Steps to a Healthier You. http://www.MyPyramid.gov.

U.S. Department of Health and Human Services and U.S. Department of Agriculture. 2005. Dietary Guidelines for Americans 2005. http://www.healthierus.gov/dietaryguidelines.

Wynnes, Katie, Sarah Stanley, Barbara McGowan, and Steve Bloom. 2005. Appetite Control. Journal of Endocrinology 184: 291318.

Carmen R. Isasi

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Nutrition

NUTRITION

Adequate research plays a crucial role in preserving the health status and functional independence of older adults. Conversely, malnutrition is associated with an increased rate of morbidity, mortality, and a failure to thrive in the elderly population.

Factors affecting adequate nutrition in elderly individuals

There are a number of factors that manifest in older age that may adversely effect nutritional status and promote significant weight and muscle loss. This weight loss, or anorexia of aging, is associated with further deterioration in nutritional status, increased hospitalization and disease rates, and premature death.

Factors influencing nutritional status in elderly persons may be divided into three categories: psychological, social, and medical. For instance, psychological disorders such as depression and dementia are highly correlated with loss of body weight in nursing homes and are the major causes of weight loss in free-living elderly individuals. In addition, numerous studies have suggested that social isolation, low socioeconomic status, and poverty are also associated with reduced dietary intake and weight loss. Moreover, numerous medical factors such as the use of prescription medicines, poor dentition, institutionalization, a decrease in taste and smell sensations, and an inability to regulate food intake have all been suggested to decrease appetite and adversely affect nutritional status in older adults.

Challenges in assessing energy requirements

There are numerous problems that have hindered the establishment of nutritional recommendations in older adults. These problems are due, in part, to the reliance on measuring caloric intake to derive daily energy needs. Research has shown that when validated against newly developed techniques, the older methods used to assess caloric intake, such as self-recorded diaries, dietary interviews, and twenty-four-hour dietary recalls, consistently underestimate actual daily energy needs. In addition, the heterogeneity of the elderly population presents additional challenges. For instance, the current recommended daily allowances (RDAs) are suggested for individuals up to age fifty and to those over fifty-one years of age. However, this broad categorization of persons over fifty-one years does not take into consideration the numerous physiological differences and differing nutritional needs of individuals within this broad age group.

An alternative to assessing energy requirements by using energy intake methodologies is the utilization of daily energy expenditure, or the sum of calories burned throughout the course of a day. When an individual is weight stable, daily energy expenditure can be used as a proxy measure of daily energy needs.

Daily energy expenditure is comprised of three components: resting metabolic rate, the thermic effect of feeding, and the thermic effect of physical activity. Resting metabolic rate represents the greatest proportion of daily energy expenditure (6075 percent), and is a measure of the energy required to sustain homeostasis and basic physiological functions. The thermic effect of feeding constitutes approximately 10 percent of daily energy expenditure and represents the energy cost of digesting, absorbing, storing, and metabolizing a meal. The most variable component of daily energy expenditure is the thermic effect of physical activity (1550 percent), which includes the energy expended through both voluntary exercise and involuntary activities, such as shivering, fidgeting, and postural control. Research has suggested that age is associated with a decrease in all three of these components of daily energy expenditure.

A new and more accurate method to assess energy expenditure is the doubly labeled water technique, which was first validated for use in humans in the 1980s. This technique involves the oral administration of two isotopes of water (deuterium and oxygen-18), and is based on the fact that deuterium labeled water is lost from the body through the usual routes of water loss (urine, sweat, evaporation), whereas oxygen-18 labeled water is eliminated from the body not only as water, but also as carbon dioxide. Approximately one to three weeks following administration of the isotopes, urine samples are collected and analyzed to calculate carbon dioxide production, which is determined by the difference in the turnover rates of the two isotopes. Carbon dioxide production, in turn, is used to determine oxygen consumption, and hence energy expenditure.

The advantages of the doubly labeled water technique are: 1) it provides an accurate, noninvasive assessment of daily energy expenditure in the free-living environment; 2) measurements are performed over extended periods of time (two to three weeks), which helps account for the daily perturbations in energy expenditure; and 3) when used in combination with indirect calorimetry, it is possible to assess the thermic effect of physical activity. The disadvantages of the method lie mainly in its cost, which makes it impractical for widespread use in large-scale studies. Despite this limitation, however, doubly labeled water provides a more accurate measure of energy requirements than previous methods.

To support this claim, a 1996 summary of six studies utilizing doubly labeled water concluded that energy requirements in older individuals may be higher than the given recommendations. Other studies have also concluded that current recommendations underestimate energy needs of older, Caucasian men and women and African American men, but not African American women. These studies suggest that doubly labeled water may help us understand true energy needs and alleviate the various problems that have hindered the development of adequate nutritional recommendations for elderly persons. Furthermore, studies highlight the heterogeneity of the elderly population and the necessity to focus on the development of individual, rather than group, recommendations.

Summary and future considerations

Due to the pivotal role proper nutrition plays in preserving health, preventing morbidity and premature death in older adults, and the myriad of factors that can compromise nutritional status in older age, there is a critical need to provide well-founded recommendations for age-related changes in energy requirements. However, the heterogeneity of the aging population, along with the inaccuracy of traditional energy intake methods to assess energy requirements, have hindered the development of such recommendations.

The development of the doubly labeled water technique has enabled the accurate measurement of daily energy expenditure in free-living individuals. The majority of doubly labeled water studies have suggested that current recommendations may underestimate the actual energy needs of the elderly population. Despite the cost, long-term longitudinal studies utilizing this new method are needed to accurately assess the age-related changes in energy requirements.

Christopher L. Gentile Eric T. Poehlman

See also Congregate and Home-Delivered Meals; Malnutrition; Sarcopenia; Taste and Smell.

BIBLIOGRAPHY

Roberts, S. B. "Energy Requirements of Older Individuals." European Journal of Clinical Nutrition 50 (1996): S112S118.

Starling, R. D., and Poehlman, E. T. "Assessment of Energy Requirements in Elderly Populations." European Journal of Clinical Nutrition 54 (2000): S104S111.

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nutrition

nutrition (new-trish-ŏn) n.
1. the study of food in relation to the physiological processes that depend on its absorption by the body. The science of nutrition includes the study of diets and deficiency diseases.

2. the intake of nutrients and their subsequent absorption and assimilation by the tissues. Patients who cannot be fed in a normal way can be given either nutrients by tubes into the intestines (enteral n. or feeding) or a nutrient solution that does not require digesting by infusion into a vein (parenteral n. or feeding). total parenteral n. (TPN) the provision of all the essential nutrients to a patient by intravenous infusion of a solution containing amino acids, glucose, fat, electrolytes, trace elements, and vitamins via a central venous catheter.
http://www.nutrition.org.uk Independent evidence-based advice on healthy eating from the British Nutrition Foundation

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Nutrition

Nutrition

Nutrition refers to the manner in which the body makes use of food. It not only includes eating the correct amounts and kinds of foods, but also the processes by which the body uses food substances for growth, repair, and maintenance of body activities. Nutrition also concerns the role that food plays in our lives and the many factors that determine our food choices.

Good nutrition during adolescence is very important for the achievement of full growth potential and optimal health as well as for the prevention of certain adult chronic (frequently recurring) diseases. Poor eating habits formed during childhood and the teen years may, in combination with other factors, increase the risk for chronic diseases later in life such as heart disease, osteoporosis (a disease that causes bones to become fragile), and some forms of cancer. Eating habits also affect the risk for immediate health problems including iron deficiency anemia (a blood disease), high blood pressure, and tooth decay.

Food is basic to survival, and people have built-in mechanisms in their bodies that work to control how much they eat, when they eat, and what they eat. In addition to these built-in mechanisms, there are many other factors that affect the way people eat. What, when, and how much people eat is greatly influenced by emotional, social, cultural, and economic factors. However, eating too much, too little, or not eating some of each type of food can make people unhealthy.

Good nutrition is a complex issue that not only has immediate benefits but also is an investment in a person's future health. Adolescence is a critical period for establishing the foundation for healthful eating patterns.

EATING WELL: WHY IT'S IMPORTANT


Throughout history humans have written about food and its effect on the body. In recent years people have learned more and more about nutrition through laboratory studies conducted on animals and humans. The role of nutrition in health and disease has been recognized from research as early as 1900, although much remains to be learned.

Eating Well: Why It's Important: Words to Know

Body set-point theory:
The set point theory of weight control holds that the body will defend a certain weight regardless of external factors, such as calorie intake or exercise.
Calcium:
A mineral in the body that makes up much of the bones and teeth, helps nerve and muscle function, as well as the body's ability to convert food into energy.
Calorie:
A unit of energy contained in the food and liquids that people consume.
Carbohydrate:
The body's primary energy source, carbohydrates are the body's fuel.
Cholesterol:
A cousin to fat, is a steroid found only in foods that come from animals, such as egg yolks, organ meats, and cheese.
Chronic disease:
An illness that is present for a long time. A frequently recurring disease, such as asthma.
Enzyme:
Protein molecules that further chemical reactions in the body.
Fat:
Part of every cell membrane and the most concentrated source of energy in one's diet, fat is used by the body to insulate, cushion, and support vital organs.
Gallstone:
Stones made up of cholesterol or calcium that form in the gallbladder.
Heart disease:
When arteries become clogged with a fatty buildup; this can cause a heart attack or a stroke.
Hormone:
Substances found in the body's glands that control some of the body's functions, such as growth.
Iron-deficiency anemia:
When the body is lacking in the right amount of red blood cells, caused by a deficiency of iron.
Kidney stone:
Stones made of calcium or other minerals that form in the kidney or the ureter, which leads to the bladder.
Metabolism:
The rate at which the body uses energy.
Mineral:
A nutrient that helps regulate cell function and provides structure for cells.
Nutrient:
Food substances that nourish the body.
Obesity:
A condition marked by too much body fat.
Osteoporosis:
A disease that causes bones to become fragile.
Protein:
An organic substance made of amino acids that are necessary for human life.
Saturated fat:
Fat that is solid at room temperature.
Unsaturated fat:
Fat that is liquid at room temperature, like vegetable oil.
Vegan:
A strict vegetarian who doesn't eat any animal by-products or any dairy.
Vegetarian:
A person who lives on a diet free of meat products; some vegetarians will eat eggs or dairy products, while others will not.
Vitamin:
A nutrient that enables the body to use fat, protein, and carbohydrates effectively.

By choosing healthy eating habits, people will gain many rewards. Eating healthy foods helps people maintain a healthy weight while also providing them with plenty of energy. Not only will people feel better and have more energy when eating well, but their skin, teeth, and hair will also reflect their good choices. The choices people make now can also affect their health later in life. People's risk for developing major health problems such as heart disease, stroke, diabetes, and cancer can be reduced if they make the right food choices a part of their lives. Good nutrition will help people to look and feel their best today and help prevent some of the deadliest health problems in the future. An unhealthy diet, lack of regular physical activity, smoking, and the over-consumption of alcohol are the leading contributors to premature death in the United States. It's important to eat wellgood nutrition can save lives.

To better understand the diet link in health and disease, government agencies continue to study nutrition. Many controversies remain and a lot still needs to be explained; however, general guidelines have been developed to illustrate what Americans can do through proper diet to ensure good health.

Nutrients

Just as a car needs gasoline, a form of fuel, to run, people need food for fuel every day. Food is the source of all nutrients needed for life. Nutrients are substances used by the body for fuel, growth, and all body processes. The body needs more than fifty different nutrients every day to maintain proper health. Nutrient needs are higher in adolescence than any other time in the life cycle because the body is experiencing its biggest growth spurt at this time.

The nutrients people get from food are vitamins, minerals, carbohydrates, fats, protein, and water. People's bodies need all of these nutrients to remain healthy. Calories people eat come from fat, carbohydrates, and protein. Fat, carbohydrates, and protein are essential nutrients, which means people need them for good health. Vitamins and minerals are necessary for good health but have no calories. The body depends on good food choices to get all of these nutrients in the right amounts every day.

FAT. Fat provides the most concentrated source of energy in our diet. It also provides flavor and texture to foods. Fat in the body functions to insulate, cushion, and support vital organs and is a part of every cell membrane. Fat in our diet mainly comes from fatty meats, whole milk and whole milk dairy products (such as yogurt), butter, and baked goods. Fat can be saturated (solid at room temperature) or unsaturated (liquid at room temperature).

CARBOHYDRATES. Carbohydrates are the fuel the body needs to function. The brain primarily uses carbohydrates as its energy source. Most carbohydrates are plant-based from grains, fruits, and vegetables. There are three types of carbohydrates: sugar, starch, and fiber.

PROTEIN. Proteins act as the building blocks of the body. The body uses protein to make and maintain body tissue such as muscles and organs. It also functions as the key component of enzymes and hormones. Milk, eggs, cheese, meat, and fish are the most common sources of protein, although beans and nuts are good sources as well.

VITAMINS. Vitamins are needed in the right amounts by the body for normal growth, digestion, mental alertness, and resistance to infections. They enable the body to use fat, protein, and carbohydrates. There are thirteen different vitamins, four of which are stored in fat.

MINERALS. Like vitamins, minerals are needed in small amounts by the body. They help regulate cell function and provide structure for cells. There are fifteen minerals needed by the body; the most common ones are calcium, phosphorous, and magnesium.

WATER. Next to oxygen, water is most important to life. A person's body is 50 to 70 percent water. Although people can live for weeks without food, they can exist for only a few days without water. People need eight to ten cups of water each day.

Calories

Calories are units of energy contained in the foods people eat. The amount of calories a food has reflects how much energy it supplies to the body. The more calories a food has, the more energy it contains. The body needs energy to do everything from breathing and pumping blood to walking and running. If people eat more calories than their body burns, their body stores the excess energy as body fat.

DIETARY GUIDELINES FOR AMERICANS

The Dietary Guidelines for Americans take into account all of the currently known information about nutrition as well as the various controversies. These guidelines were issued jointly by the United States Department of Agriculture and the United States Department of Health and Human Services in 1995. The guidelines contain general health suggestions and dietary recommendations to help promote and maintain wellness.

These dietary guidelines give people direction in making better food choices to improve their health but they don't answer all of the questions of how to eat a more healthful diet. The Food Guide Pyramid was created to help better explain how to achieve the dietary guidelines.

Dietary Guidelines for Americans

Eat a variety of foods. It is important to eat a variety of foods from the different food groups each day. No two foods contain exactly the same nutrients in the same amounts. Varying the types of fruits, vegetables, grains, milk, or protein foods eaten each day helps people get all of the important nutrients their body requires.

Balance good nutrition with physical activity. Being an active person is just as important as eating healthful foods. Inactivity and poor nutrition are the leading risk factors associated with health problems later in life such as heart disease, high blood pressure, and diabetes. Being underweight can also pose serious health risks because it can mean the body isn't getting the essential nutrients it needs.

Choose a diet low in fat, saturated fat, and cholesterol. Eating a lot of foods high in saturated fat (fat that is solid at room temperature) can lead to the clogging of arteries, which can begin in the childhood years. When arteries become clogged with a fatty buildup, it is called heart disease. Heart disease can lead to a heart attack or stroke, two of the leading causes of premature death in the United States.

Choose a diet with plenty of grain products, vegetables, and fruits. Most grain foods, vegetables, and fruits are naturally low in fat and are packed with vitamins, minerals, and carbohydrates. Whole grain products, fruits, and vegetables also contain fiber, a nutrient important for good digestive health. A healthy diet is one that is based on these three food groups.

Choose a diet moderate in sugars. Filling up on sugary foods leaves less room for healthier foods with more vitamins and minerals. Foods high in sugar are often also high in fat and have been shown to cause tooth decay.

Choose a diet moderate in salt and sodium. Most people eat more salt than is needed. Excess salt in the diet has been shown to contribute to high blood pressure in people at a high risk for developing high blood pressure.

If you drink alcoholic beverages, do so in moderation. [Consumption of alcoholic beverages by minors is illegal and NOT recommended for children or teenagers under any circumstances.] Alcohol provides calories but few or no nutrients, can alter judgement, and can lead to a dependency or addiction. For adults, it is recommended that alcohol be consumed in moderate amounts.

Only the nutrients fat, protein, and carbohydrates contain calories and therefore provide energy. Vitamins and minerals don't actually supply calories but are vital in the processing of the energy-producing nutrients. Fat provides the most energynine calories per gram. Protein and carbohydrate both provide four calories per gram. A gram is roughly the same weight as a paper clip.

THE FOOD GUIDE PYRAMID


Adolescents need a practical guide to help them make food choices to meet their nutritional needs. During the twentieth century and especially in recent years, several food guides have been developed by a number of government agencies. Currently, the Food Guide Pyramid is the most widely accepted food guide that incorporates the recommendations of the Dietary Guidelines for Americans.

The Food Guide Pyramid was created to help Americans choose a healthful diet. The guide addresses two main dietary problems: diet excesses and diet deficiencies. Several of the major causes of death in the United States are linked to diets that contain too much fat, saturated fat, cholesterol, or sodium. On the other hand, bodies need enough protein, vitamins, minerals, and fiber to grow and stay healthy. People who eat too many foods with a lot of calories but few or no nutrients, like soft drinks and candy, can develop nutrient deficiencies.

The food pyramid depicts six food categories and emphasizes that the American diet should include greater amounts of grain foods, fruits and vegetables, and lesser amounts of fats and sugars. Its shape is very important to its message, as it visually represents how much food people need from each of the six categories. Each group is equally important, but people need foods from the bottom in larger amounts than foods closer to the top of the pyramid. The food pyramid emphasizes the following key points:

  • Eat a variety of foods every day.
  • Choose foods with less fat and sugar.
  • Eat plenty of whole grain foods, fruits and vegetables (preferably raw).

While the food pyramid divides foods into six categories, there are five major food groups. The food category at the tip of the pyramid is not considered a major food group since these foods should be used sparingly for good health. The food pyramid reminds people to eat a variety of foods to get all of the nutrients they need as well as the right amount of food to maintain

a healthy weight. The foods are grouped together according to the key nutrients they provide. Foods provide many more nutrients besides their key nutrients but by eating plenty of foods with key nutrients, people are more likely to get the correct balance of all nutrients.

The food pyramid also provides information on how much to eat from each group. It recommends a range of servings needed each day from each of the major food groups. The amount of calories and key nutrients people need determines how many servings they should have. A serving is a specific amount of food, which is different for each food category. The amount of calories or energy people need depends on how old they are, how active they are, and how much they weigh.

In general, boys need more energy than most girls and therefore more servings. This is due to the fact that boys have more muscle and bone growth during adolescence, which requires a higher consumption of protein, iron, calcium, and zinc. For girls, adolescence means a smaller increase in muscle mass and an increase in fatty tissue because the body is preparing for menstruation. This results in a lower need for girls than boys for certain nutrients. However, girls do need more iron and calcium because of the onset of menstruation.

As people age, they need fewer servings due to a decrease in activity level and other factors. To get all the nutrients and enough energy each day, almost everyone needs to eat at least the minimum number of servings for each group every day.

FOOD GROUP KEY NUTRIENTS SUPPLIED
Bread, Cereals, Rice and Pasta Complex carbohydrates, fiber
Vegetables Vitamins A and C
Fruits Vitamins A and C
Milk and Milk Products Calcium
Meat and Meat Alternatives Protein and iron

Bread, Cereal, Rice and Pasta Group

A healthy diet begins with plenty of foods from the bread, cereal, rice, and pasta group (which will be referred to as the grain group since all are made from grains such as wheat, oats, corn, or rice). It is recommended that people eat between six and eleven servings per day from this group. As such, this group is at the bottom of the pyramid and forms the base, or foundation, of a healthy diet. People need more servings each day from this group than from any other. The grain group of foods provides the nutrients complex carbohydrates (starch and fiber), vitamins, and minerals to the body.

The choices people make from this group are significant because carbohydrates, especially those from whole grain sources, can play an important part in healthful eating. Complex carbohydrates are the starches that come mainly from plant foods such as wheat, oats, and rice. Fruits and vegetables also provide complex carbohydrates. Complex carbohydrates provide your body with its preferred source of energy. There is a common misconception that the foods from this group are fattening. In fact, most grain group foods are low in fat and calories. Donuts, pastries, muffins and some crackers (butter or cheese flavored) can be quite high in fat and are the few exceptions. What can increase the amount of fat and calories is what people add to grain foods. For example, the butter or cream cheese people may use on a bagel can (depending on how much is used) nearly double the calories from this grain food.

Fiber is the tough or stringy part of plant foods like grains, fruits, and vegetables, therefore sometimes referred to as "roughage." People do not digest most dietary fiber, and so it gets pushed through the digestive tract helping the body rid of wastes. To get the fiber the body needs, the type of grain group foods people choose is very important. Grains high in fiber include whole wheat bread, brown rice, whole-wheat crackers, pasta, and whole grain cereals (like Cheerios, Raisin Bran, and Shredded Wheat).

Vegetable Group and Fruit Group

It is recommended that everyone eat at least five servings per day from this category. Fruits and vegetablesespecially raw (or uncooked) fruits and vegetableshelp reduce the risk for heart disease and some cancers by providing important vitamins and minerals as well as a good source of fiber. Fruits and vegetables are also naturally low in fat and calories, help maintain a healthy weight, and decrease the risk of diabetes and high blood pressure. Two of the vitamins that are particularly important to health that fruits and vegetables provide are Vitamins A and C.

GRAIN GROUP CHOICES

Typical grain foods include bread, cereal, popcorn, pretzels, flour tortillas, rice, noodles, and crackers. Each of the following counts as one serving from the grain group:

  • 1 slice of bread
  • 1/2 hamburger or hot dog bun
  • 1 ounce cold cereal
  • 1/2 cup of pasta, rice or hot cereal
  • 3 to 4 saltine-type crackers

Vitamin A is important for: night vision, healthy skin, gums and teeth. Good sources of Vitamin A are: carrots, sweet potatoes, spinach, grapefruit, cantaloupe, and nectarines. Vitamin C is important for healthy gums and teeth, healing cuts and scrapes, and strong bone development. Good sources of Vitamin C are: broccoli, tomatoes, green pepper, 100% orange juice, pineapple, and peaches.

Most Americans don't get enough servings of fruits and vegetables every day. The National Cancer Institute and Department of Health and Human Services has been promoting increased consumption of fruits and vegetables through a program called "5 A Day for Better Health." Research has suggested that people who eat lots of fruits and vegetables may have lower risks for some cancers than people who eat less. The fiber, vitamins, and other components in fruits and vegetables may be responsible for this lower risk.

Eating a variety of fruits and vegetables every day is important since they all don't provide the same vitamins and minerals in the same amounts. Besides the vast number of different fruits and vegetables, fruit juice and vegetable juice are also considered servings from these groups. Many beverages on the market today call themselves juice but are mostly based on a sugar-sweetened liquid with only a small amount of fruit juice added. Consumers should be sure to look for the words "100% fruit or vegetable juice" on the label of juices to be sure that they contain all of the benefits of a fruit or vegetable serving.

Milk and Milk Products Group

It is recommended that two to three servings from this group be consumed per day.

The milk and milk products group includes milk, yogurt, and cheese. The key nutrient supplied by this group is the mineral calcium, but milk and milk products also provide protein, carbohydrates, and other vitamins and minerals. Vitamin D is an important component in milk because a body needs vitamin D in order to properly absorb calcium. As a result, all milk sold in stores is fortified with Vitamin D.

FRUIT & VEGGIE CHOICES

Each of the following counts as a serving from the vegetable group:

  • 1/2 cup cooked or chopped raw vegetable
  • 1 cup lettuce or salad greens
  • 3/4 cup vegetable juice
  • 10 French fries

Each of the following counts as a serving from the fruit group:

  • 1 medium piece of fruit or melon wedge
  • 1/2 cup 100% fruit juice
  • 1/2 cup chopped, cooked or canned fruit

There are many choices when it comes to buying milk at the grocery store or even in the school cafeteria. There are four types of milk, which differ only in the amount of fat and calories they contain. All four types of milk provide the same amount of calcium and other nutrients. Water is not added to low fat or nonfat milk, although people tend to think this because the

milk may seem "watery" if they are used to drinking milk with higher fat content (milk with higher fat content tends to be thicker or creamier than nonfat milk).

MILK GROUP CHOICES

Each of the following counts as a serving from the milk and milk products group:

  • 1 cup milk or yogurt (preferably low-fat)
  • 1 cup frozen yogurt
  • 1-1/2 ounces of natural cheese (cheddar, Swiss)
  • 2 ounces of processed cheese

A WORD ABOUT CALCIUM

More than 80 percent of teenagers, particularly girls, do not get enough calcium. Calcium is very important for building strong bones, improving nerve impulses and blood clotting and muscle contractions. During the teen years, people need more calcium because they're growing taller and bone development shifts into high gear. Nearly half of all bone is formed during the teenage years. Calcium is deposited in bones when people eat food rich in calcium. Calcium is withdrawn from bones when people are not receiving enough calcium; similar to the way people do their banking, calcium is deposited and withdrawn from bones on a continual basis and it is perfectly normal to withdraw from time to time. Teens and others run into problems, though, when more calcium is continually withdrawn than is deposited, meaning that teens are not getting enough of this important nutrient. When teenagers do not meet the daily requirement for calcium, their bones may not reach their full potential. What results is bone that is less dense (like Swiss cheese) and less able to withstand the natural loss that comes with aging.

When bone loss is excessive, bones can become brittle and weak and are more likely to fracture or break. This condition is referred to as osteoporosis, or "porous bones." People are more likely to develop osteoporosis later in life if they do not reach their bone potential by getting enough calcium during the teen years. Nearly 25 million Americans have osteoporosis and four out of every five are women.

Most teenagers don't meet the requirement for calcium because of poor eating habits, meal skipping, and dieting. Two to three servings from the milk and dairy food groups each day are all that is needed to meet the daily requirement, although there is some debate over this; certain nutritionists believe that four servings of dairy a day may be more appropriate for teens. Milk drinking often declines during the teen years as soda and sweetened beverage intake goes up. Other foods in the food pyramid besides milk and dairy foods can also provide calcium, but milk is still the best source.

According to health experts, in order to get all of the nutrition milk has to offer without getting too much fat or calories, anyone above the age of two should be drinking low-fat milk. One cup of whole milk (4% fat) has the same amount of fat as three strips of bacon. Babies and children under two years of age need that extra fat in their diets for growth and development. Most adults, teens, and schoolage children should drink low fat or nonfat milk. Low-fat (1% fat) and nonfat milk (skim milk) are excellent sources of calcium without a lot of fat and calories.

Type of Milk Fat (per 1 cup) Calories (per 1 cup)
Whole milk (4%) 8 grams 150 calories
Reduced fat milk (2%) 5 grams 120 calories
Low-fat milk (1%) 2.5 grams 100 calories
Nonfat milk (skim) 0 80 calories

Experts recommend that if people find it difficult to adjust to drinking low-fat milk, they should try switching to reduced-fat milk (2%) first. Then, when they have adjusted to the change, they can make the healthy switch to low-fat or nonfat milk.

Meat and Meat Alternatives Group

The meat and meat alternatives group provides the key nutrients protein and iron. Protein is needed for maintaining muscles, and iron is needed for healthy blood. This is perhaps the most diverse food group of them all because it includes not only red meat, like steak or hamburger, but poultry, fish and seafood, eggs, beans, nuts, and peanut butter as well. These foods are considered alternatives or substitutes for meat because they are all good sources of the key nutrients protein and iron. It is recommended that two to three servings from this group be consumed each day.

In general, most Americans get enough protein each day, and usually more than they need. The foods in this group are often thought of as being high in fat and cholesterol. Some choices in this group are much higher in fat than others and should be chosen less often. Highest fat choices include bologna, salami, hot dogs, regular ground beef, fried chicken, and sausage. Lean meat, chicken and turkey without the skin, fish, and beans are the best to choose most often because they are lower in fat.

Individuals who follow a vegetarian (meatless) diet must take care to incorporate protein into their diets. People choose to be vegetarian for a variety of reasons: religion, culture, or love of animals. Whatever the reason, foods such as nuts, eggs, seeds, beans, peanut butter, tofu or possibly fish would replace meat or poultry as protein sources in their diet. If it is planned carefully to make sure important nutrients are not lacking, a vegetarian diet can be a healthy and adequate diet.

Fats, Oils, and Sweets

The small tip of the Food Guide Pyramid shows fats, oils, and sweets and is not considered a major food group. These foods provide fat, sugar, and calories but few nutrients and should be enjoyed as occasional extras, not in place of foods in the major food groups. The foods found in this group include salad dressing, butter, margarine, soda, candy, chips, and sweet desserts. Although fat is an essential nutrient needed for good health, there is no recommended number of servings provided for this group. Eating foods from the major food groups should provide all of the fat people need. The foods in this category should be used sparingly.

MEAT/PROTEIN GROUP CHOICES

Each of the following counts as a serving from the meat/protein group:

  • 3 ounces (about the size and thickness of a deck of cards) cooked meat or poultry or fish
  • 1/2 cup cooked beans
  • 1 egg
  • 2 tablespoons peanut butter

The Facts on Fat

Fat is an essential nutrient needed for good health. Most Americans, however, eat too much of it. Fat has been given a great deal of attention in recent years for two reasons. First, fat provides more calories than any other nutrient. Second, a fatty diet can promote heart disease, cancer, and obesity (being very overweight) and is the biggest nutrition concern among Americans. Not all fats are created equal, however. There are two major types of fat: saturated fat and unsaturated fat. There is also a substance known as cholesterol, but it is not the same as fat.

SATURATED FAT. Saturated fat is also referred to as the "bad" fat because it is the type that is responsible for clogging the arteries and raising blood cholesterol levels. Saturated fats are fats that are solid at room temperature, such as margarine, butter, lard, or the fats in and on meat. In comparison, unsaturated fats are liquids. Foods that contain a lot of saturated fat are ground beef, bacon, sausage, hot dogs, bologna, whole and 2% milk, cheese, ice cream, and butter. Many baked goods and snack foods are also high in saturated fats.

UNSATURATED FAT. Unsaturated fat is also known as the "good" fat because it does not clog arteries. But that does not mean people can eat all of the unsaturated fat they want. Too much fat of any kind can be unhealthy. Unsaturated fats are fats that are liquid at room temperature like vegetable oil.

CHOLESTEROL. Cholesterol, a cousin to fat, is a steroid found only in foods that come from animals, like egg yolks, organ meats, and cheese. Foods low in cholesterol are not necessarily low in fat. An example is vegetable oil; it is 100 percent fat but has no cholesterol because it comes from a plant and not an animal.

MORE ON IRON

The mineral iron is needed to keep your blood healthy. It delivers oxygen to all of your body tissues. A low iron level in the blood is called iron-deficiency anemia and is very common during the teenage years. It is more common in girls who are menstruating than in boys, but it remains a common nutrition problem among this age group. Having anemia (low iron levels in the blood) means that blood has the reduced ability to carry oxygen to the body's cells and tissues. This can result in feeling tired, an inability to tolerate a usual amount of activity or exercise, headaches, dizziness, and feeling short of breath. It can also affect schoolwork because being tired all the time makes it more difficult to perform well in school.

To prevent anemia, include iron-rich foods at every meal. Vitamin C helps the body absorb iron from foods better and should be eaten with ironrich foods. Not all foods from the meat and meat alternatives group are good sources of iron, however. The best sources are chicken and red meat. Beans, peanut butter, and foods from other food groups such as cereals, spinach, and raisins are also good sources of iron.

Saturated fat and cholesterol in food can raise the body's blood cholesterol level. A high blood cholesterol level is one of the risks for heart disease. Heart disease is the clogging of the arteries, and it happens over a long period of time. It starts in the teen years and can eventually lead to a heart attack or stroke if it goes unchecked. The American Heart Association recommends a diet that provides less than 30 percent of its calories from fat. People can slow down or stop the buildup of fat and cholesterol in their arteries by making good food choices now. On the other hand, people should remember that the body still needs some fat to be healthy. Following a completely fat-free diet is harmful to a person's overall health. A fat-free diet also won't guarantee that a person won't get heart disease.

Although people do need some fat in their diets, most people get too much, especially the saturated kind. For best health, people should try to eat fewer higher fat foods. If a person follows the guidelines of the food pyramid and eats plenty of whole grains, vegetables and fruits, it isn't difficult to eat the right amount of fat. In addition, one should select milk and dairy foods made from low-fat or skim milk as well as skinless poultry, fish, and lean cuts of meat. Higher fat food choices need to be balanced with lower fat ones so that it all evens out at the end of the day.

WHAT MAKES A HEALTHY DIET?


For a healthy diet, one should:

  • Eat more fruits and vegetables. Fruits and vegetables are naturally low in fat, are filling, and can help reduce cravings for higher fat snacks and treats.
  • Use low-fat or nonfat milk and milk products. Milk, yogurt, cheese, and frozen desserts made from low-fat or nonfat milk will help to reduce the intake of fat.
  • Eat lean meats that are baked, broiled, boiled or grilled instead of fried.
    Choose these more often: Choose these less often:
    Tuna packed in water Tuna in oil
    Baked fish and steamed seafood Fried fish and seafood
    White meat chicken and turkey Dark meat chicken and turkey
    Low-fat hot dogs Regular hot dogs
    Turkey or lean ham Bologna or salami lunchmeats
    Canadian bacon or lean ham Bacon
    Turkey or low-fat sausage Regular sausage
    Lean ground beef Regular ground beef
  • Try lower fat versions of some high-fat favorites:
    Try: Instead of:
    Low-fat frozen yogurt ice cream
    Low-fat salad dressing regular salad dressing
    Low-fat mayonnaise mayonnaise
    Baked tortilla chips fried tortilla chips
    Flavored rice cakes high-fat crackers
    Low-fat cream cheese cream cheese
    Low-fat fruit yogurt regular yogurt
  • Add less fat to foods. Mayonnaise, butter, cream cheese, gravy and salad dressings can add a hefty amount of fat to a meal. Try to use less of these products or find a replacement (mustard instead of mayo, jam instead of butter, etc.) or try the low-fat version to cut back on fat.

JUNK FOOD


Americans eat a lot of sugar. In fact, the average person in the United States consumes 130 pounds of sugar a year. This is the equivalent of 1/4 cup of sugar a day. Almost 25 percent of the calories the average person consumes each day comes from sugar. This far exceeds what health experts recommendless than 10 percent.

Sugars are a form of carbohydrates. There are two types of carbohydrates, simple and complex. Simple refers to single units of sugar like table sugar. Complex carbohydrates are starches and fiber found in grain foods, fruits, and vegetables. During digestion, all carbohydrates are broken down to sugar. When most people think of sugar, they think only of white table sugar. However, sugars do occur naturally in many foods like milk, fruits, and vegetables. Less than 10 percent of the sugar that Americans consume is from natural sources. The rest is from "junk food," such as candy, soda, or processed foods.

SUGAR CONTENT OF COMMON SWEETS

To help give some perspective on the amount of sugar in each of these items, imagine dumping this many spoonfuls of sugar on to your morning bowl of cereal:

12-ounce can of soda 611 teaspoons
8 ounces of Kool-Aid 6
Candy bar (1 ounce) 7
1 cup sugar-coated cereal 6
1 cup chocolate milk 3
1 piece of cake with frosting 7

The major nutritional concern about sugar is that it can displace other more nutritious foods in a person's diet. Sugar provides calories but no essential nutrients by itself. If people consume a lot of sugary foods, they may not have room for foods that provide vitamins, minerals, and other essential nutrients. A diet high in sugar does not cause hyperactivity as many people claim. Nor is it the cause of diabetes (a disease that disables the body from controlling the level of sugar in the blood). The only disease that sugar causes is tooth decay.

SNACKING


People often think of snacking as something bad and unhealthy. As a result, they often try to prevent eating between meals. However, snacking can be an important part of a healthy diet depending on the choices people make. Many health experts recommend fueling up on several mini-meals throughout the day instead of eating three big meals. The right snacks can help boost energy levels and help people get the well-balanced variety of foods they need each day.

Snacking is not part of a healthy diet if a person fills up frequently on fatty, sugary foods. Snacks such as soda, chocolate candy, chips, cookies, cakes, doughnuts, and ice cream are not what a person should reach for first when looking for a snack. Filling up on these kinds of snacks leaves little room for the other foods people need. Even if people eat the foods they do need along with these snacks, they will probably end up with too much fat and calories in their diets. An excess of calories and fat can be harmful to a person's health. Snacks like soda, chips, chocolate and candy are okay in moderation, but snacks from one of the major food groups should be the first choice. Looking at food labels can also help a person make good snack choices. Good snack choices mean nutrient-dense snacks.

GOOD SNACK CHOICES

  • Cereal with low-fat milk
  • Pretzels, baked tortilla chips
  • Vanilla wafers
  • Raw veggies dipped in salsa, hummus, or low-fat salad dressing
  • Fresh fruit dipped in low-fat yogurt
  • Fruit-flavored low-fat yogurt
  • Light microwave popcorn
  • Canned fruit, packed in its own juices
  • 100% fruit juice
  • Frozen yogurt or sorbet
  • Pudding made with low-fat milk
  • Graham crackers or animal crackers
  • Low-fat granola bars
  • Banana with peanut butter

A nutrient-dense food is a food that provides a good source of nutrients in relation to its calories. For example, a cup of broccoli, a piece of custard pie, and a half-ounce of cheddar cheese all provide similar amounts of the mineral calcium. The pie by far has the most calories, the broccoli the least. The broccoli has the highest nutrient density for calcium because it provides the most calcium for the least amount of calories, which is most beneficial for the body's health. Healthy snacking means combining snacks from the different groups in the food pyramid, such as a banana with low-fat yogurt to meet a fruit and a milk serving. It's important to try to eat fewer snack foods that provide little in the way of nutrients. These snacks are usually high in calories, fat or sugar (or all three) and low in vitamins, minerals, and complex carbohydrates.

Moderation Is the Key

All foods can fit into a healthy diet. The key to healthy eating is balance, variety, and moderation. This means eating a variety of foods without getting too many calories or too much of any one nutrient, especially fat. If portion sizes are kept reasonable it's easy to eat the foods one wants and stay healthy. Favorite foods need only be reduced, not completely eliminated from the diet. Most people eat for pleasure as well as nutrition. If favorite foods are high in fat and/or sugar, the key is to moderate how much and how often they are eaten.

Not every food and every meal has to be perfect for a person to be healthy. When eating foods high in fat, salt, or sugar one should also choose foods that

aren't. If one food group is missed one day, it can be made up for the next. Food choices over several days should fit together into a healthy eating pattern.

Foods are not "good" or "bad," but a diet can be. People should not feel bad if they enjoy foods such as ice cream, candy, or chips. Favorite foods can be eaten in smaller quantities less frequently, balancing them with healthier choices to provide the variety and balance that is important in a healthy diet.

FOOD, WEIGHT, AND BODY SHAPE


Most people believe that nutrition and food are closely connected to weight and body shape. While this is true to a certain extent, it certainly does not represent the whole picture. A person's weight and body shape are not solely determined by how much a person eats or exercises. In fact, a person's body shape is determined most by the body shape of his or her parents. In addition, experts recently began questioning the role of weight and fat in relation to disease and illness. More needs to be studied, but researchers believe now that it's possible to be fit and healthy even if a person appears to be over-weight. In other words, having excess fat on the body does not automatically make a person unhealthy.

A Lesson in Genetics

Nearly 55 percent of adults are considered overweight or obese in America today. It is believed that when people eat more calories than their body uses, they gain weight. Simple as it may seem, not all people who are over-weight overeat. Most overweight teens do not eat more than their healthy weight peers do. The difference appears to lie in the level of activity. Genetics also can play a part. Genes are responsible for much of the way a person looks and acts. To a certain degree, they can also influence whether a person will be overweight or not. Although people may be able to improve their health by eating well and exercising, their body type and weight is dictated mostly by genetics.

Body type seems to be related to body weight. In the 1940s, scientist William H. Sheldon proposed a theory to characterize three basic body types. An endomorph is characterized by an increased proportion of body fat; a mesomorph by a muscular build; and an ectomorph by lack of much fat or muscle. An endomorph would have difficulty losing weight, have a soft body and round shape. The mesomorph would have a hard, muscular body and could gain or lose weight easily. An ectomorph would have a thin, delicate build and trouble gaining weight. Not every person will fit exactly into one category.

Having an excess of body fat can carry with it some health risk factors. Not only the amount of excess fat but the location of fat on a person's body is of importance. Women typically gain weight in their hips and buttocks giving them a pear shape. Men usually build up body fat around their bellies giving them an apple shape. Although this is not a hard and fast rule, there is evidence that people with fat in their abdomen, men or women, are more likely to develop many of the health problems associated with being over-weight or obese, such as heart disease and type-II diabetes.

People whose parents are obese tend to be overweight as well. Having parents who are overweight will increase a person's chance of being over-weight by 25 to 30 percent. Heredity does not destine anyone to be fat, but it can influence the amount of body fat and where fat is distributed on a person's body. To avoid serious health risks, a person who is genetically predisposed to obesity should be consistently careful about eating healthfully and exercising regularly.

The Body's Set Point

The set point theory of weight control holds that the body will defend a certain weight regardless of external factors. In other words, no matter how healthfully a person eats or how much a person may exercise, he or she remains right around the same weight. Unfortunately, many people who are overweight tend to concentrate only on losing the pounds when their focus should be to improve their health. Ultimately, fitness is more important to health than what a person weighs or the amount of body fat one has. Some individuals may not be overweight even though their weight may seem high for their height. This can be due to differences in body composition. Athletes with a lot of muscle, such as Olympic skier Picaboo Street, may weigh more than they appear, but they would never be considered overweight because muscle weighs more than fat. Ultimately, a person who exercises and eats well will naturally fall to his or her set point. Trying to fight this set point may lead to frustration, depression, and unhealthy weight management practices, such as fasting and dieting.

Body Image

Looking in the mirrorwhat does one see? Is it everything or is the focus just on trouble spots? Body image is how one sees oneself, and how one believes what others see, too. Body image can say a lot about one's mental and physical well-being.

A negative body image is when one doesn't like or doesn't feel satisfied with their body. Having a negative body image can be related to low self-esteem, depression, poor health habits, or a psychological disorder. It can negatively affect feelings, behaviors, interpersonal relationships, decisionmaking ability, and day-to-day living. It takes practice to accept one's body and understand that all aspects of appearance can't be controlled. Much of a person's appearance is due to heredity.

If a person has a negative body image, that person should strive for self-improvement but be realistic. Seeking positive supportive relationships is

helpful as well as remembering that a person's sense of self-worth must come from within. Associating with people who accept themselves, recognizing that the body is only part of oneself, and focusing on positive aspects of one's personality are helpful. It's also important to practice positive self-talk often and give oneself credit for worthy accomplishments.

Food and Feelings

From the day people enter the world they have an emotional connection to food. Eating can be an emotional experience. Many people eat in response to their emotionssuch as being stressed out, tired, or boredrather than in response to internal cues that they are hungry. This is called emotional eating. People also eat in response to other external cues such as time of day, location, or social situations. People with whom we live or socialize, the places in which we carry on our lives, and our emotions largely control our eating.

"Normal" eating is defined as eating when real hunger is present and eating until one is satisfied, without feelings of guilt or becoming uncomfortably full. Normal eating is flexible and depends on internal cues to regulate it, but it also depends on good food choices to ensure good nutrition.

From birth many people are programmed to eat at certain times of the day, given food as rewards for good behavior or a job well done, or associate foods with certain holidays or social events. Many people associate eating with other behaviors such as watching television. They may find themselves frequently snacking while watching television even though they are not really hungry, because it's what they always do. And so eating "habits" are formed. Eating habits such as these can lead to overeating or eating the wrong foods. Many health experts agree that changing negative eating habits to healthier ones can help a person improve their health.

EATING DISORDERS

Eating disorders are dangerous psychological (relating to the mind) illnesses that affect millions of people, especially young women and girls. The most widely known eating disorders are anorexia nervosa and bulimia nervosa, but other eating-related disorders, such as binge-eating, exist as well. People suffering from eating disorders battle life-threatening obsessions (constant thoughts) with food and unhealthy thoughts about their body weight and shape. If untreated, these disorders can lead to serious bodily damage or even death. Recovery from an eating disorder is possible, though it is a difficult process that should be done under a doctor's supervision. The first steps toward recovery are for the sufferer to accept that there is a problem and show a willingness to focus on his or her feelings rather than on food and weight.

For more information on eating disorders, the causes and the treatments, please see Chapter 13: Eating Disorders in Volume 3 of this set.

In order to begin to change a bad food habit, a person must recognize it first. The reason many overeat or eat more than they need is because they don't recognize negative food behaviors. Experts recommend that people identify their food behaviors by keeping a food diary. A food diary is a record of the food people eat, what they were doing at the time, and how they felt. This exercise will tell people about themselves, their temptations and the emotional states that encourage them to eat and otherwise ignore internal signs of hunger.

WEIGHT MANAGEMENT AND DIETING


As stated earlier, people's body weight is mostly controlled by their bodies' set point. Weight is also somewhat affected by how often people exercise. Many people try to change their body weight through dieting, which usually involves eating less or a combination of eating less and exercising. Some people, in an effort to lose weight quickly, may take diet pills or engage in unhealthy weight management practices. Dieting is not a healthy way to control body weight. The best way to stay healthy is to eat properly and exercise regularly. With regular exercise and good nutrition, most people will naturally fall to the weight appropriate to them, that is, their set point. In fact, experts say that when people are exercising, they need more food in order to function.

FAD DIETS

Just as fads in fashion come and go, so food fads come and go. A food fad is a food or nutrition style, practice, or craze that many people adopt for a period of time. The most common food fads are related to weight loss. Usually they are the same exact diet plans that get recycled each year under a new name. Each time a promise of unbelievable weight loss is what makes the diet appealing. It may be based on special foods a person has to buy, a magical powder or drink, or a fat dissolving capsule developed to "melt away" the pounds. Fad diets usually restrict people to eating primarily one type of food and promise unbelievable weight loss in a short period of time. Fad diets are unsuccessful because they violate almost all of the principles of healthy eating.

Most food fads are short lived, but they are always replaced by a new fad. It's important to be aware of them. For example, the cabbage soup diet promises a 10- to 17-pound weight loss in just the first week of eating cabbage soup, a fat burning food. The truth is that you probably would lose weight on such a diet, but it would largely be due to loss of extra fluid (water) and because of the extreme restriction of calories. In reality, it's very difficult to eat just one food for a whole week, and it certainly isn't healthy. Sadly, with most fad diets people can spend a considerable amount of money only to be disappointed that the weight they lost (if any) reappeared as soon as they returned to their typical eating habits.

Although it may be frustrating at times when one is anxious to lose weight, it is best to lose weight slowly over a longer period of time by eating normal foods and exercising. The longer it takes to lose the weight, the more likely a person is to keep the weight off.

Dieting can be dangerous because it often deprives the body of the nutrients it needs to function properly. In addition, dieting can also cause people to gain weight. This happens because the body's metabolism (the rate at which the body uses energy) lowers in response to not getting enough food. Any food the body does receive is then stored as fat. This is a survival method used by the body to get the food it needs. When people go off diets, their metabolism is still lower, which means when they start eating more, they will store even more food as fat. The result is more weight gain. Experts recommend that dieting be avoided at all times. Being healthy and fit is a lifestyle choice. It doesn't happen on a temporary diet, and it doesn't happen by denying the body food. It happens when a person eats nutritious food and exercises.

In addition, dieting can turn dangerous when a person engages in unhealthy behaviors, such as taking diet pills, fasting (not eating over a period of time), or purging (vomiting) the food. Many times, a diet can lead to a serious eating disorder. [See Chapter 13: Eating Disorders for more information.]

Weight Loss Programs and Products

Nearly 8 million Americans enroll in structured weight loss programs each year. While some programs do succeed for some individuals, unfortunately most people fail to lose the weight permanently. The problem is that most programs don't teach people how to change their eating habits and exercise regularly to promote good health. Frequently new diet books and plans appear, usually with some gimmick offering quick, painless weight loss. Many of these diets do nothing to change food behaviors permanently or create a weight maintenance program. Most are inappropriate for lifetime eating patterns, may be nutritionally inadequate, and possibly dangerous, especially for young people. For example:

Product/Program How supposed to work Concerns
Diet pills Chemically decrease appetite or stimulate central nervous system Increase blood pressure, can dehydrate, possible dependency
Special food or combinations Grapefruit burns fat, special combinations fool your body into digesting differently and decreasing absorption of calories Not based on scientific fact, limits choices, compromises nutrition, impossible and unhealthy to maintain
Liquid drinks or package foods Control total calories eaten by replacing meals or snacks Products alone do not help you lose weight, no flexibility

Any claims by weight loss programs or products that people can lose weight effortlessly are false and unhealthy. Fad diets or diet gimmicks rarely have any lasting effects since radical changes in eating habits and patterns are difficult to maintain over time. Crash diets often send a person into a cycle of quick weight loss followed by rebound weight gain.

Beware of pills and powders claiming to burn, block, or flush fat out of the body. If it sounds too good to be true, it probably is. Some diet pills may be able to control appetite but can have serious side effects. For example, amphetaminesa common appetite suppressant found in many diet pillsare highly addictive and can have damaging effects on the heart and nervous system. There are numerous weight loss programs available today. Some are schemes that come and go and others have stood the test of time. The main thing to remember is that these programs are a business like any other and aim to make money. If one plans to join a program, it pays to do some homework first. There are a few things to know before making any financial commitments to a program:

  • Understand the program's format. Is it individual or group? Is it necessary to buy their food?
  • Does the program offer one-on-one counseling? Does it reward or punish members based on the amount of weight lost?
  • Does the program include all food groups every day? A well-balanced diet is important for good health. Beware of programs that have definitive "good" foods and "bad" foods or exclude any particular kinds of food.
  • If a program utilizes its own prepackaged foods, taste them first. It would be a terrible shame to invest time and money and find the food inedible. More important, is the packaged food healthy? Check sugar and salt levels on the packages.
  • Does the program fit into one's lifestyle? Is it affordable? Is it risky? Does the program help make positive behavior changes and encourage a safe personalized exercise program? These are the tools to help keep the weight off. If a program cannot provide these, then one should reconsider.
  • Do the counselors in the program have an education in nutrition, psychology, and exercise?

BECOMING AN INDEPENDENT EATER


As children grow older, they often become more independent in their eating patterns. During adolescence, other factors begin to influence what people eat. For example, playing sports or engaging in after-school activities can alter eating times. Going out with friends can turn eating into a social event. Unfortunately, busy schedules and busy lives can mean unhealthy eating and poor nutrition. Sometimes, a person decides to follow a special diet, such as vegetarian or vegan. When these choices are made, it's important to make sure that the body is getting all the nutrients it needs to grow and stay healthy.

VEGETARIAN AND VEGAN DIETS


Most vegetarians don't eat meat, poultry, or fish. Their diets consist mainly of plant-based foods such as vegetables, fruits, grains, legumes (peas and beans), nuts, and seeds. Eggs and dairy products may also be excluded. Vegans (pronounced VEE-ghans) don't eat any animal products including eggs, dairy, or even honey. Others who occasionally eat meat (usually chicken or fish) may also call themselves vegetarians, although they are really only part-time vegetarians.

Only about one percent of the population in the United States is vegetarian. There are many reasons why a person may choose to be vegetarian. The most influential reason for adopting a vegetarian diet worldwide is food availability. In many parts of the world plant foods are abundant whereas animal foods are scarce or too expensive. In the United States, people have adopted a vegetarian lifestyle for one of several reasons. They may believe it is more healthful, their religious or ethical beliefs exclude meat, or they may be concerned for the environment or the treatment of animals raised for consumption. Research has shown that vegetarians have lower rates of some cancers, heart disease, high blood pressure and diabetes. Vegetarians are also less likely to have gall stones, kidney stones, and constipation.

Types of Vegetarian Diets

  • Lacto-ovo vegetarian diet includes milk, milk products and eggs.
  • Lacto-vegetarian diet includes milk and milk products.
  • Vegan diet includes only plant foods.

Vegetarian diets can be healthy and adequate but may take a little more planning to ensure nutritional adequacy. This is particularly true of vegan diets. The more people restrict their diets, the more difficult it is to get all of the nutrients they need. Vegans have a difficult time getting vitamin B-12, calcium, vitamin D, and zinc because vegan diets exclude dairy and meat, both of which provide the primary sources for the aforementioned nutrients.

Becoming a vegetarian isn't as simple as some people think. It doesn't mean just excluding meat from the diet. Beginning a vegetarian diet in this manner may shortchange the body of essential nutrients important for growth and development. If one is considering a vegetarian diet for any reason, one should become educated about it and perhaps even speak with parents and doctors about a healthy eating plan. Common vegetarian foods include macaroni and cheese, spaghetti, pizza, eggplant parmesan, vegetable or bean soup, bean burritos, and peanut butter and jelly.

It's important to note, however, that growing children and pregnant or nursing women should proceed with a vegetarian diet with caution because of special nutrition needs. The key to a vegetarian dietas with any other dietis to eat a variety of foods and limit the amount of fats and sweets. One should be prepared with the right tools to get started and remember to eat the following foods to obtain these nutrients that could be lacking in a vegetarian diet that is not properly planned:

Protein: soy products, tofu, legumes (peas and beans), nuts, seeds. Calcium: milk, leafy dark green vegetables, legumes, fortified soy or rice milk, tofu. Iron: cereals and grains, leafy dark green vegetables. Vitamin B-12: dairy or eggs, supplements for vegans.

CREATING HEALTHY EATING HABITS


Eating regular meals and snacks throughout the day is very important to meeting nutritional needs. It is nearly impossible to get all nutrient needs in only one or two meals each day. This way of eating may lead to overeating and poor food choices because people may get too hungry to think clearly about what and how much they are going to eat. Irregular meals may be one of the reasons many people struggle to maintain a healthy weight. In fact, skipping meals in an effort to lose weight it is a common mistake. Depriving oneself of a meal or particular food in order to lose weight may lead to bingeing (a period of uncontrolled eating) or poor eating later in the day.

Hunger usually wins out and irrational food choices can result. Smaller, more frequent meals or snacks is a sensible way to remain energized and get all of the servings needed from the five food groups each day.

Don't Forget Breakfast

The meal most often neglected by teenagers is breakfast. It is an easy meal to skip as people rush to get out the door to school or to work, but breakfast really is the most important meal of the day. Breakfast literally means to "break a fast" (a fast is a period where little or no food is eaten), in which the fasting period is the time that the person was sleeping. A person's body needs fuel in the morning to help spark metabolism. Breakfast fuels people up with enough energy to learn and be active throughout the day. It can help to keep concentration at a better level and energy high. Breakfast can make a difference in how a person feels all day. Quick and easy breakfast ideas include granola bars, bagels, English muffins, cereal, and frozen waffles. A glass of milk and juice or fruit balances it out.

SAMPLE EATING PLAN FOR TEENS

Breakfast

1 cup cereal (grain)

3/4 cup orange juice (fruit)

1 slice wheat toast with jam (grain/extra) or peanut butter (meat)

1 cup low-fat milk (milk)

Lunch

23 slices ham (meat)

2 slices wheat bread (grain)

1 teaspoon low-fat mayonnaise (extra)

Carrot and celery sticks (vegetable)

Apple (fruit)

1 cup low-fat chocolate milk (milk)

Snack

1 cup low fat fruit yogurt (milk)

3 Fig Newton cookie bars (grain)

Dinner

Grilled chicken breast (meat)

Tossed salad with low-fat salad dressing (vegetable/extra)

1 cup rice or noodles (grain)

1/2 cup spinach (vegetable)

Dinner roll with margarine (grain/extra)

1 cup low-fat milk (milk)

Snack

Light microwave popcorn (grain)

1/2 cup fruit juice or 1 serving fresh fruit (fruit)

Remembering the dietary guidelines' recommendations and utilizing the food pyramid is the key to a healthy diet. Spend lots of time at the bottom of the pyramid, less time at the top, and choose carefully from the middle. Drink plenty of water each day and balance food choices with exercise to help maintain a healthy weight.

FOR MORE INFORMATION


Books

Herbert, Victor and Genell J. Subak-Sharpe, eds. Total Nutrition: The Only Guide You'll Ever Need. New York: St. Martin's Press, 1995.

Larson, Roberta. The American Dietetic Association's Complete Food and Nutrition Guide. Chicago: Chronimed Publishing, 1996.

Levchuck, Leslie. Fuel Up!: A Girl's Guide to Eating Well. New York: The Rosen Publishing Group, 1999.

Web sites

5 A Day for Better Health. [Online] http://www.5aday.com (Accessed October 29, 1999).

E Nutrition. [Online] http://www.enutrition.com (Accessed October 29, 1999).

Mayo Clinic Nutrition Center. [Online] http://www.mayohealth.org/mayo/common/htm/dietpage.htm (Accessed October 29, 1999).

The Vegetarian Resource Group. [Online] http://www.vrg.org (Accessed October 29, 1999).

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Nutrition

Nutrition

Nutrition is the science that studies the interactions between living organisms and food. Human nutrition includes the study of nutrients and other substances found in foods; how the human body uses nutrients for growth and maintenance; and the relationship between foods, food components, dietary patterns, and health. The study of nutrition encompasses all aspects of the ingestion, digestion, absorption, transport, metabolism, interaction, storage, and excretion of nutrients by the body. In a broader sense, the study of nutrition also includes the various psychological, sociological, cultural, technological, and economic factors that affect the foods and dietary patterns chosen by an individual.

Beth Fontenot

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nutrition

nutrition The origin of the term nutrition, and of ‘nutrients’, refers to all substances necessary for growth and for the maintenance of life and health of the body tissues. In this sense, not only food but also water and oxygen can be called nutrients, and their provision can be called nutrition. But in common usage, nutrition means provision of substances in food and drinks. These include the ‘fuels’ for metabolic energy production and the raw materials necessary for growth, repair, and maintenance of the body's fabric — carbohydrates, proteins and fats — and also the vitamins and minerals essential for these processes.

Stuart Judge


See diets; food.

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COLIN BLAKEMORE and SHELIA JENNETT. "nutrition." The Oxford Companion to the Body. 2001. Encyclopedia.com. 27 Sep. 2016 <http://www.encyclopedia.com>.

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nutrition

nu·tri·tion / n(y)oōˈtrishən/ • n. the process of providing or obtaining the food necessary for health and growth: a guide to good nutrition. ∎  food; nourishment: a feeding tube gives her nutrition and water. ∎  the branch of science that deals with nutrients and nutrition, particularly in humans: she took a short course in nutrition | [as adj.] nutrition experts. DERIVATIVES: nu·tri·tion·al / -shənl/ adj. nu·tri·tion·al·ly / -shənl-ē/ adv.

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nutrition

nutrition Processes by which plants and animals take in and make use of food substances. The science of nutrition involves identifying the kinds and amounts of nutrients necessary for growth and health. Nutrients are generally divided into proteins, carbohydrates, fats, minerals, and vitamins. Plants use materials from the abiotic (nonliving) environment, a process known as autotrophic nutrition, while animals use food from the biotic (living) environment, a process called heterotrophic nutrition.

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"nutrition." World Encyclopedia. 2005. Encyclopedia.com. 27 Sep. 2016 <http://www.encyclopedia.com>.

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nutrition

nutrition The process by which organisms obtain energy (in the form of food) for growth, maintenance, and repair. There are two main types of nutrition: heterotrophic nutrition, employed by animals, fungi, and certain bacteria; and autotrophic nutrition, found in most plants and bacteria.

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"nutrition." A Dictionary of Biology. 2004. Encyclopedia.com. 27 Sep. 2016 <http://www.encyclopedia.com>.

"nutrition." A Dictionary of Biology. 2004. Encyclopedia.com. (September 27, 2016). http://www.encyclopedia.com/doc/1O6-nutrition.html

"nutrition." A Dictionary of Biology. 2004. Retrieved September 27, 2016 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O6-nutrition.html

nutrition

nutrition The process by which living organisms take in and use food for the maintenance of life, growth, the functioning of organs and tissues; the branch of science that studies these processes.

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DAVID A. BENDER. "nutrition." A Dictionary of Food and Nutrition. 2005. Encyclopedia.com. 27 Sep. 2016 <http://www.encyclopedia.com>.

DAVID A. BENDER. "nutrition." A Dictionary of Food and Nutrition. 2005. Encyclopedia.com. (September 27, 2016). http://www.encyclopedia.com/doc/1O39-nutrition.html

DAVID A. BENDER. "nutrition." A Dictionary of Food and Nutrition. 2005. Retrieved September 27, 2016 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O39-nutrition.html

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