FUNCTIONAL FOODS. The term "functional foods" refers to foods and their components that may provide a health benefit beyond basic nutrition. Functional foods do more than meet minimum daily nutrient requirements—they also can play a role in reducing the risk of disease and promoting good health. Biologically active components in functional foods impart health benefits or desirable physiological effects.
All foods have a function when consumed in proper balance as part of an overall healthy diet. Functional foods may include whole foods, such as fruits and vegetables, which represent the simplest example. Those foods that have been fortified, enriched, or enhanced with nutrients, phytochemicals, or botanicals, as well as dietary supplements, also fall within the realm of functional foods.
The functional attributes of many traditional foods are only now being discovered. Examples include phytoestrogens in soy foods and a variety of antioxidants in fruits and vegetables, such as lycopene in tomatoes. Still, new food products are being developed with beneficial components, with a focus on wellness and the reduced risk of chronic disease (i.e., foods and beverages containing pre-and probiotics to maintain gastrointestinal health, calcium-fortified beverages to maintain bone health, and dressings and spreads containing plant stanol and sterol esters, which may decrease the risk of heart disease).
Over two thousand years ago Hippocrates said, "Let food be thy medicine." Although the concept of functional foods is not entirely new, it has evolved considerably over the years. In the early 1900s food manufacturers in the United States began adding iodine to salt in an effort to prevent goiter, representing one of the first attempts at creating a functional food through fortification.
Other twentieth-century examples include vitamin A and D fortification of milk and niacin and folic acid fortification of grains. These early fortification examples, however, focused on reducing the risk of diseases of deficiency. In the latter part of the twentieth century, consumers began to focus on wellness and the reduction of chronic disease. Research now focuses frequently on the promotion of health through many lifestyle factors, including the consumption of an optimal diet. As of 2002, researchers have identified hundreds of food components with functional qualities, and they continue to make new discoveries surrounding the complex benefits of phytochemicals in foods.
Consumer interest in the relationship between diet and health has increased the demand for information on functional foods. Rapid advances in science and technology, increasing health-care costs, changes in food laws affecting label and product claims, an aging population, and a rising interest in attaining wellness through diet are among the factors fueling U.S. interest in functional foods. Credible scientific research indicates many potential health benefits from food components. These benefits could expand the health claims now permitted by the U.S. Food and Drug Administration (FDA).
The International Food Information Council (IFIC) has been researching awareness of, and attitudes about, functional foods, through both qualitative and quantitative research. In 2002 telephone surveys with U.S. consumers were conducted, building on quantitative data collected in 1998 and 2000.
As in 1998 and 2000, the vast majority of consumers believe that they have a "great amount" of control over their own health. Also, in comparing the effects of nutrition, exercise, and family health history on health, consumers believe that nutrition plays the greatest role (71 percent versus 63 percent and 41 percent, respectively). Therefore, it is no surprise that 93 percent of Americans believe that some foods have health benefits that go beyond basic nutrition and that 85 percent are interested
|Examples of functional components *|
|Class/Components||Source *||Potential benefit|
|Alpha-carotene||carrots||Neutralizes free radicals that may cause damage to cells|
|Beta-carotene||various fruits, vegetables||Neutralizes free radicals|
|Lutein||green vegetables||Contributes to maintenance of vision|
|Lycopene||tomatoes and tomato products (ketchup, sauces, etc.)||May reduce risk of prostate cancer|
|Zeaxanthin||eggs, citrus, corn||Contributes to maintenance of vision|
|Collagen Hydrolysate||gelatin||May help alleviate some symptoms associated with osteoarthritis|
|Insoluble fiber||wheat bran||May reduce risk of breast and/or colon cancer|
|Beta glucan**||oats||Reduces risk of cardiovascular disease (CVD)|
|Soluble fiber**||psyllium||Reduces risk of CVD|
|Whole grains**||cereal grains||Reduce risk of CVD|
|Omega-3 fatty acids, DHA/EPA||tuna; fish and marine oils||May reduce risk of CVD and improve mental, visual functions|
|Conjugated linoleic acid (CLA)||cheese, meat products||May improve body composition, may decrease risk of certain cancers|
|Anthocyanidins||fruits||Neutralize free radicals, may reduce risk of cancer|
|Catechins||tea||Neutralize free radicals, may reduce risk of cancer|
|Flavanones||citrus||Neutralize free radicals, may reduce risk of cancer|
|Flavones||fruits/vegetables||Neutralize free radicals, may reduce risk of cancer|
|Glucosinolates, Indoles, Isothiocyanates|
|Sulphoraphane||cruciferous vegetables (broccoli, kale), horseradish||Neutralizes free radicals, may reduce risk of cancer|
|ferulic acid||fruits, vegetables, citrus||Antioxidantlike activities, may reduce risk of degenerative diseases like heart disease and eye disease|
|Stanol/stanol ester**||corn, soy, wheat, wood oils||May reduce the risk of coronary hear disease (CHD) by lowering blood cholesterol levels|
|Fructo-oligosaccharides (FOS)||Jerusalem artichokes, shallots, onion powder||May improve gastrointestinal health|
|Lactobacillus||yogurt, other dairy||May improve gastrointestinal health|
|Saponins||soybeans, soy foods, soy protein-containing foods||May lower LDL cholesterol, contains anticancer enzymes|
|Soy Protein**||soybeans and soy-based foods||1 ounce per day may reduce risk of heat disease|
|Isoflavones, daidzein, genistein||soybeans and soy-based foods||May reduce symptoms of menopause, such as hot flashes|
|Lignans||flax, rye, vegetables||May protect against heart disease and some cancers; lowers LDL cholesterol, total cholesterol, and triglycerides|
|Diallyl sulfide||onions, garlic, olives, leeks, scallions||Lowers LDL cholesterol, maintains healthy immune system|
|Allyl methyl trisulfide, dithiolthiones||cruciferous vegetables||Lowers LDL cholesterol, maintains healthy immune system|
|Proanthocyanidins||cranberries, cranberry products, cocoa, chocolate||May improve urinary tract health and reduce risk of CVD|
| *Examples are not an all-inclusive list. |
** FDA-approved health claim established for component.
in learning more about such foods. These levels of interest have been consistently strong since 1998.
The top ten foods that consumers identify as having a health benefit beyond basic nutrition include broccoli (9 percent), fish or fish oil (9 percent), green, leafy vegetables (9 percent), oranges or orange juice (9 percent), carrots (8 percent), garlic (7 percent), fiber (6 percent), milk (6 percent), calcium (5 percent), oats/oat bran/oat-meal (6 percent), and tomatoes (6 percent). The top five foods have remained consistent for the past three surveys; they are associated with America's top health concerns. Cardiovascular disease factors, including heart disease/attack, high blood pressure, stroke, and high cholesterol, remain the primary collective concern of American consumers. Cancer continues to concern almost a third (30 percent) of all consumers. Other areas of worry include weight (17 percent), diabetes (17 percent), and nutrition/diet (12 percent).
Almost two-thirds (63 percent) of Americans say they are eating at least one food in order to receive a functional health benefit. Although not significantly different from the 2000 results (59 percent), this does represent a significant increase since 1998 (53 percent).
Finally, the terms "functional foods" and "nutraceuticals" are often used to describe foods that may have health benefits beyond basic nutrition. "Functional foods" is preferred over "nutraceuticals" two to one (62 percent versus 31 percent). In reality, all foods have some function even if it is mostly taste and enjoyment. In addition, health benefits can be reaped from an apple, yogurt, or a filet of salmon as much as from calcium-fortified fruit juice or a supplement.
Many academic, scientific, and regulatory organizations are considering ways to establish the scientific basis to support claims for functional components or the foods containing them. FDA regulates food products according to their intended use and the nature of claims made on the package. Three types of claims are allowed on food and dietary supplement labels: (1) structure and function claims describing effects on the normal function of the body; (2) disease risk-reduction (health) claims implying relationships between components in the diet and diseases or health conditions, as approved by FDA and supported by significant scientific agreement; and (3) content claims.
Whereas science can confirm broad connections between some foods or eating patterns and health benefits, it is still not known how all individual food components work and whether there are synergistic effects among compounds. For example, numerous studies suggest that the consumption of a diet rich in whole grains, fruits, and vegetables is associated with a decreased risk of prostate, bladder, esophageal, stomach, and other cancers. However, the interactions among various components in these foods continue to be elucidated. The roles of vitamins, minerals, fiber, antioxidants, and other phytonutrients do not stand alone.
A large body of credible scientific research is needed to confirm the benefits of any particular food or component. Although scientific studies point to many functional components in foods that provide added health benefits, more research is needed to determine which components are responsible for the beneficial effects as well as how individual components interact. The scientific community is still in the early stages of understanding the potential for functional foods. For functional foods to deliver their potential public-health benefits, consumers must have a clear understanding of and a strong confidence level in the scientific criteria that are used to document health effects and claims.
Functional foods are an important part of wellness, which includes a balanced diet and physical activity. The good news with functional foods is that what one does eat may be more important for health than what one does not eat. Individuals should consume a wide variety of foods, including the examples listed in Table 1. These examples are not "magic bullets." The best advice is to include a variety of foods from each of the food groups, which would incorporate many potentially beneficial components.
See also Biotechnology; Food Safety; Fruit; Health and Disease; Hippocrates; Nutraceuticals; Vegetables .
What Is the Relationship between Food Biotechnology and Functional Foods?
Although many of the nutritional compounds in functional foods are either naturally present or added during processing, some may be the result of agricultural breeding techniques, including conventional cross-breeding and, in the future, food biotechnology.
Crossbreeding to produce a plant for a specific genetic trait, such as higher sulforaphane-containing broccoli, can take as long as a decade or more. Modern biotechnology, however, makes it possible to select a specific genetic trait from any plant and move it into the genetic code of another plant in a much shorter time span, and with more precision than cross-breeding allows.
Researchers are working with farmers around the world to develop dozens of functional foods through the use of this promising technology. For example, a high-oleic acid soybean oil has been developed through biotechnology to have the health benefits of soybeans (possible protection against heart disease) without the saturated fat content of other cooking oils. Other research holds promise for boosting levels of beneficial components such as carotenoids in fruits and vegetables.
How Can More Functional Foods Be Added to the Diet?
The most effective way to reap the health benefits from foods is to eat a balanced and varied diet, including whole grains, lean meats, low-fat dairy products, legumes, fruits and vegetables, as well as foods with added beneficial components. Watch labels and read articles for information about foods and health. Before deciding to make any major dietary changes, however, take the time to evaluate your personal health and speak to your health-care provider on ways to help reduce the risk of certain diseases. It is also important to remember that there is no magic bullet that can cure or prevent health concerns, even when eaten in abundance. The best advice is to choose foods wisely from each level of the food guide pyramid in order to incorporate many potentially beneficial components into the diet.
Where Can Additional Information about Functional Foods Be Found?
- International Food Information Council: http:/ific.org/functional.
- Functional Foods for Health Program, University of Illinois: http://www.ag.uiuc.edu/ffh.
- "Position of the American Dietetic Association: Food Fortification and Dietary Supplements." Journal of the American Dietetic Association 101 (2001): 115–125. Available at http://www.eatright.org/imags/journal/0101/adapt0101.pdf.
- Position of the American Dietetic Association: "Phytochemicals and Functional Foods." Journal of the American Dietetic Association 99 (1999): 1278–1285. Available at http://www.eatright.org/adap1099.html.
- FDA Consumer Report: "Staking a Claim to Good Health." November/December 1998. Available at http://vm.cfsan.fda.gov/dms/fdhclm.html.
- IFT Scientific Status Summary: "Functional Foods: Their Role in Disease Prevention and Health Promotion." November, 1998. Available at http://www.ift.org/publications/sss/funcfood.pdf.
- FDA/CFSAN: "Dietary Supplements Overview." Available at http://www.cfsan.fda.gov/dms/supplmnt.html.
- FDA/CFSAN: "Claims That Can Be Made for Conventional Food and Dietary Supplements." Available at http://www.cfsan.fda.gov/dms/hclaims.html.
Functional foods are foods that provide health benefits beyond basic nutrition due to certain physiologically active components, which may or may not have been manipulated or modified to enhance their bioactivity. These foods may help prevent disease, reduce the risk of developing disease, or enhance health. Consumer interest in functional foods increased during the late twentieth century as people's interest in achieving and maintaining good health increased. Health-conscious consumers have become aware of the health benefits associated with specific foods and are incorporating elements such as fiber , calcium , and soy into their diets. Rapid advances in food science and technology, an aging population, the rapid rise in health care costs, and changing government marketing and labeling regulations have also had an impact on the functional foods market.
There is a difference between the Western and Eastern perspective on functional foods. In the West, functional foods are considered revolutionary and represent a rapidly growing segment of the food industry. Food and pharmaceutical companies alike are competing to bring functional foods into the mass market. On the other hand, functional foods have been a part of Eastern cultures for centuries. Foods were used for medicinal purposes in traditional Chinese medicine as early as 1000 b.c.e. From ancient times, the Chinese have used foods for both preventive and therapeutic health effects, a view that is now being increasingly recognized around the world.
Clearly, most foods are functional in some way. What makes a "functional food," however, is its potential ability to positively affect health. Functional foods range from fruits, vegetables, and whole grains, which are naturally high in phytochemicals , to products in which a specific ingredient is added, removed, increased, or decreased. Examples of functional foods include soy, oats, flaxseed, grape juice, broccoli and other cruciferous vegetables, phytosterol/stanol-enriched margarine, eggs enhanced with omega-3 fatty acids , foods fortified with herbal preparations, and psyllium .
Regulations Related to Functional Foods
Functional foods are regulated by the United States Food and Drug Administration (FDA) under the authority of two laws. The Federal Food, Drug, and Cosmetic Act (FD&C) of 1938 provides for the regulation of all foods and food additives . The Dietary Supplement Health and Education Act (DSHEA) of 1994 amended the FD&C Act to cover dietary supplements and ingredients of dietary supplements. Functional foods may be categorized as whole foods, enriched foods, fortified foods, or enhanced foods. Labeling claims that are used on functional foods are of two types: (1) Structure and function claims, which describe effects on normal functioning of the body, but not claims that the food can treat, diagnose, prevent, or cure a disease (claims such as "promotes regularity," "helps maintain cardiovascular health," and "supports the immune system " fit into this category); and (2) Disease-risk reduction claims, which imply a relationship between dietary components and a disease or health condition.
Structure and function claims do not require preapproval by the FDA, and they require much less stringent scientific consensus than disease-risk reduction claims. Under the FD&C Act, structure and function claims cannot be false or misleading. However, the law does not define the nature or extent of evidence necessary to support these claims. To complicate matters, the evidence available to support structure and function claims varies widely
|Functional food||Potential health benefit||Labeling claim|
|Oats||Reduces cholesterol and constipation, reduces risk of heart disease||May reduce the risk of heart disease|
|Soy||Reduces cholesterol, reduces risk of osteoporosis, certain cancers, and heart disease||May reduce the risk of heart disease|
|Fruits and vegetables||Reduces risk of certain cancers and heart disease; reduces hypertension||May reduce the risk of some cancers; May reduce the risk of heart disease|
|Fish||Reduces cholesterol and triglycerides||None|
|Garlic||Reduces risk of heart disease and certain cancers, reduces cholesterol||None|
|Grapes/grape juice||Reduces risk of heart disease||Structure/function claim|
|Flaxseed||Reduces risk of heart disease and certain cancers; reduces triglycerides; increases blood-glucose control||None|
|Nuts||Reduces risk of heart disease||None|
|Grains||Reduces risk of certain cancers, heart disease, and nutrient deficiencies||May reduce the risk of some cancers; May reduce the risk of heart disease|
|Juices with calcium||Reduces risk of osteoporosis, reduces hypertension||Helps maintain healthy bones and may reduce risk of osteoporosis|
|Grains with folic acid||Reduces risk of heart disease and neural tube birth defects||May reduce risk of brain and spinal cord birth defects|
|Infant formulas with iron||Reduces risk of iron deficiency||None|
|Grains with added fiber||Reduces risk of certain cancers and heart disease; reduces cholesterol and constipation; increases blood-glucose control||May reduce the risk of some cancers; May reduce the risk of heart disease|
|Milk with vitamin D||Reduces risk of osteomalacia and osteoporosis||Helps maintain healthy bones and may reduce risk of osteoporosis|
|Juices with added fiber||Reduces risk of certain cancers and heart disease; reduces cholesterol, hypertension, and constipation||May reduce risk of some cancers|
|Dairy products with probiotics||Reduces risk of colon cancer and candidal vaginitis; controls inflammation; treatment of respiratory allergies, diarrheal disorders, and eczema||Structure/function claim|
|Beverages and salad dressings with antioxidants||May support overall health||Structure/function claim|
|Foods and beverages containing herbal preparations||Varies with ingredients||Structure/function claim|
|Sports bars||Varies with ingredients||Structure/function claim|
|Spreads with stanol esters||Reduces cholesterol||Structure/function claim|
|Foods containing sugar alcohols in place of sugar||Reduces risk of tooth decay||May reduce risk of tooth decay|
|Eggs with omega-3 fatty acids||Reduces risk of heart disease||Structure/function claim|
because some ingredients have been studied extensively, some have not been studied very much, and some ingredients are backed by mixed results.
Disease-risk reduction claims, typically called health claims, do require FDA approval before they can be used on products and must reflect scientific consensus. For example, the health claim for soy protein and its relation to cardiovascular disease reads: "Diets low in saturated fat and cholesterol that include 25 grams of soy protein a day may reduce the risk of heart disease . One serving of (name of food) provides ____ grams of soy protein." This claim may appear only on soy products that provide at least 6.25 grams of soy protein per serving. Other FDA-approved health claims include those related to fruits and vegetables and a reduced risk of cancer ; saturated fat and an increased risk of heart disease; sodium and increased risk for hypertension , and folic acid–fortified foods and reduced risk of neural tube defects.
Many developed functional foods seem to have benefits for human health. For example, calcium-fortified orange juice provides approximately the same amount of calcium as milk. With more than half of all children under the age of five and nearly 85 percent of females age twelve to nineteen not meeting the Dietary Reference Intake (DRI) for calcium, calcium-fortified orange juice may contribute significantly to calcium intake. On the other hand, a positive impact on health is more difficult to establish for other developed functional foods. These include prepared foods spiked with herbal preparations, which may contain little of the herbal ingredients listed on the label, or insufficient quantities of these ingredients to produce the claimed effect. Additionally, some herbal ingredients can be harmful, such as kava, which has been associated with liver damage, and belladonna, which is toxic.
The future of functional foods will undoubtedly involve a continuation of the labeling and safety debates. As consumers become more health conscious, the demand and market value for health-promoting foods and food components is expected to grow. Before the full market potential can be realized, however, consumers need to be assured of the safety and efficacy of functional foods. Future research will focus on mechanisms by which food components such as phytochemicals positively affect health, and whether these components work independently or synergistically. According to the American Dietetic Association, dietetics professionals will be increasingly called upon to develop preventive meal plans, to recommend changes in food intake, to enhance phytochemical and functional food intake, and to evaluate the appropriateness of functional foods and dietary supplements to meet preventive (and therapeutic) intake levels for both healthy persons and those diagnosed with disease.
see also Antioxidants; Phytochemicals.
M. Elizabeth KunkelBarbara H. D. Luccia
American Dietetic Association (1999). "Functional Foods—Position of the ADA." Journal of the American Dietetic Association 99:1278–1285. Also available from <http://www.eatright.org>
Mazza, G., ed. (1998). Functional Foods: Biochemical and Processing Aspects. Lancaster, PA: Technomic Publishing.
Wildman, Robert E. C., ed. (2001). Handbook of Nutraceuticals and Functional Foods. Boca Raton, FL: CRC Press.
NUTRACEUTICALS. There are many ways to think about food. In the simplest sense, food is fuel. Food provides the energy needed to perform daily functions and maintain normal metabolic processes. But we all know that food is more than fuel. Food contains nutrients that are essential to prevent diseases. For example, scurvy will occur if vitamin C is not continually present in the human diet. Similarly, blindness can occur where diets are deficient in vitamin A. The "essential nutrients"—those that are needed to prevent specific diseases—have been a major focus of human nutrition research for the past century. Through this research we have determined the amount of each essential nutrient required to prevent disease in populations of various ages, cultures, and genetic predispositions. What is interesting, however, is that the link between diet and disease, or more important, diet and health, cannot be entirely explained by the absence or presence of the various essential nutrients in our diets. And so today, a multitude of components that are found in foods are being investigated to determine what, if any, role they play in maintaining health and reducing the risk of disease. Numerous phytochemicals (plant chemicals) that occur in fruits and vegetables are taking center stage in this research, as more evidence accumulates regarding their health-promoting properties (Beecher, 1999).
Human Nutrition Research
Concurrent with these new activities in nutrition research is a reevaluation of the medicinal practices of past and present cultures. These traditional medicines are based largely on the use of plant materials. Chinese medicine, which predates modern medicine by thousands of years, employs a vast array of botanical materials for the treatment of disease and the maintenance of health. Similarly, East Indian Ayurvedic medicine, early European folk medicine, and native North American medicine are based largely on the use of plant materials.
Today the exploration and exploitation of the diseasefighting properties of a multitude of phytochemicals found in both food and nonfood plants have created a renaissance in human health and nutrition research. At the same time, many opportunities for the development of novel dietary products have been created. With all new fields of study come new terms. "Nutraceuticals" and "functional foods" are two new terms used to describe health-promoting foods or their extracted components. Although debate continues regarding the exact meaning of these terms, it is convenient to consider nutraceuticals as healthful products that are formulated and taken in dosage form (for example, capsules, tinctures, or tablets). Functional foods, on the other hand, are products that are consumed as foods, and not in dosage form.
The beneficial role of many nutraceuticals and functional foods may relate to their protective effects against degenerative diseases, such as cancer and cardiovascular disease. Typically the active ingredient(s) in the food or supplement is believed to help the body combat metabolic processes that lead to degenerative conditions. In this way, supplementing the diet with beneficial phytonutrients may reduce the risk of degenerative diseases during aging. These concepts are well illustrated by the example of dietary antioxidants.
There is overwhelming evidence to suggest that oxygen and its highly reactive by-products are responsible for oxidative damage ("rust") to biomolecules in our bodies. Oxidative damage to biomolecules is believed by many to be a significant factor in the etiology of many degenerative diseases and the aging process itself. Oxidative damage to cellular DNA is an underlying element in the initiation of cancer. Similarly, oxidative damage to low-density lipoprotein in the blood is a causal agent in the development of atherosclerotic plaque in cardiovascular disease. It has been suggested and supported by various types of evidence that consuming antioxidants may provide greater protection against the deleterious effects of oxidative damage (Ames et al., 1993).
Several groups of plant phytochemicals, including carotenoids, tocopherols, and polyphenolics, are extremely effective antioxidants; these antioxidants are found at various levels in fruits, vegetables, and nonfood plants. Thus, with respect to the terms "nutraceutical" and "functional foods," a fresh or processed fruit or vegetable that is particularly high in antioxidant phytochemicals could be considered a functional food. The high antioxidant level may be a normal characteristic of the plant, or may be due to phytochemical fortification during manufacture of a processed food product. A nutraceutical may be an antioxidant phytochemical concentrate, having been extracted from raw materials and formulated as a standardized capsule or tablet (Hasler, 1998).
Challenges and Opportunities
The field of nutraceuticals and functional foods is new, and many gaps exist in the knowledge base. For example, it is widely accepted that the health-promoting properties of foods are not necessarily due to single components, but rather a few or several active ingredients. This creates a significant paradigm shift from the pharmaceutical model, which is based on the efficacy of single agents. Many of the bioactive phytochemicals under investigation have long been ignored, thus methods for their handling and measurement are lacking. Manufacturers wish to make specific claims of health benefits on their product labels. Clearly such claims must be based on solid scientific evidence, which to date is often lacking. Government regulatory bodies also face challenges in this new category of health products, which lies between foods and drugs. However, all parties share the desire to improve personal and public health through diet modification, to reap the consequent social and economic benefits.
The field of nutraceuticals and functional foods is at times confused, or at least lumped together with the field of biotechnology and genetic modification. The two areas are distinctly different, although there is some potential for overlap. Techniques in genetic modification may be applied to enhance the phytochemical content of food and nonfood plants. Although the complex series of biochemical reactions used by plants to synthesize specific phytochemicals is often not well understood, there is tremendous potential to harness the plant's sophisticated biochemical machinery to synthesize valuable compounds and ultimately enhance human health.
See also Antioxidants; Biotechnology; Crop Improvement; Dietary Assessment; Dietary Guidelines; Ethnobotany; Ethnopharmacology; Functional Foods; Genetic Engineering; Vitamins.
Ames, Bruce N., Mark K. Shigenaga, and Tory M. Hagen. "Oxidants, Antioxidants and the Degenerative Disease of Aging." Proceedings of the National Academy of Science USA 90 (1993): 7915–7922.
Beecher, Gary R. "Phytonutrients' Role in Metabolism: Effect on Resistance to Degenerative Processes." Nutrition Reviews 57, no. 9 (1999): S3–S6.
Dixon, Richard A., and Christopher L. Steele. "Flavonoids and Isoflavonoids—A Gold Mine for Metabolic Engineering." Trends in Plant Science 4, no. 1 (1999): 394–400.
Hasler, Clare M. "Functional Foods: Their Role in Disease Prevention and Health Promotion." Food Technology 52, no. 11 (1998): 63–70.
Joseph, James A., Barbara Shukitt-Hale, Natalia A. Denisova, Donna Bielinski, Antonio Martin, John J. McEwan, and Paula C. Bickford. "Reversals in Age-Related Declines in Neuronal Signal Transduction Cognitive, and Motor Behavioral Deficits with Blueberry, Spinach, or Strawberry Dietary Supplementation." Journal of Neuroscience 19, no. 18 (1999): 8114–8121.
Foods and supplements are also being examined for their effects on neurodegenerative processes. Blueberries have recently been shown to reverse some of the losses in memory and motor skills that occur during aging (Joseph et al., 1999). Gingko biloba supplementation may be effective in the prevention and treatment of Alzheimer's disease.
Anticancer and Cardioprotective Properties
The anticancer and cardioprotective properties of plant flavonoids and isoflavonoids are being investigated in human health and nutrition research. In the field of biotechnology, genetic techniques are being developed to control the synthesis of flavonoids and isoflavonoids in various food crops (Dixon and Steele, 1999).