Nutrition describes the processes by which all of the food a person eats are taken in and the nutrients that the body needs are absorbed. Good nutrition can help prevent disease and promote health.
Vitamins and minerals are an important part of nutrition. Vitamins are organic substances present in food. They are required by the body in small amounts to regulate metabolism and to maintain normal growth and functioning. Minerals are vital because they are the building blocks that make up the muscles, tissues, and bones. They also are important to many life-supporting systems, such as hormones, transport of oxygen, and enzyme systems.
There are many nutrients the body absorbs from food and each of the food groups supplies at least one nutrient. For example, oat bran, which is a whole grain, can supply fiber and a mineral called magnesium. A good nutrition plan will ensure that a balance of food groups, and the nutrients supplied by each group, is eaten
Percentage of healthy, overweight, and obese adults in the United States
|Age 20> yrs||Healthy weight BMI 18.5 to 24.9||Overweight BMI 25.0–29.9||Obese BMI 30 and above|
source: National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, U.S. Department of Health and Human Services.
(Illustration by GGS Information Services/Thomson Gale.).
As children, nutrition is important for normal growth and development. As adults, nutrition still promotes health and reduces risk of disease. Studies have shown that Americans have gained weight largely because they eat too much and because they choose to eat the wrong foods. Good nutrition can help prevent weight gain by focusing on consuming calories that are high in nutrients, not in sugars and fat. Nutrition also plays a role in preventing and controlling diseases. For example, poor nutrition can lead to high cholesterol, which causes coronary heart disease. Lowering salt in the diet can control high blood pressure. People with diabetes must follow special diets to control their blood glucose levels.
Examples of people with medical conditions and diseases show the effect that certain nutrients, or a lack of certain nutrients, can have on the human body. Some specific diseases linked to poor diet and physical inactivity are cardiovascular disease, type 2 diabetes, high blood pressure, osteoporosis , and certain types of cancer. Being overweight, and especially obese, also is linked to many health problems. Eating a poorly balanced diet that is low in nutrients but high in total calories can lead to weight gain.
Special diets or nutritional therapy may be used to complement other treatments subscribed by a physician to treat particular diseases and conditions. Examples include:
- High cholesterol. Eating a diet high in fiber and low in saturated fats and cholesterol can help keep cholesterol in check.
- High blood pressure. Reducing salt and certain fats, as well as reducing overall weight, helps lower blood pressure. Special diets have been developed to lower risk of high blood pressure and heart disease.
Monounsaturated fat— Fats that contain one double or triple bond per molecule. Though these fats still have lots of calories, they can help lower blood cholesterol if used in place of saturated fats. Examples of monounsaturated fats are canola oil and olive oil.
Polyunsaturated fat— Fats that contain two or more double or triple bonds per molecule. Examples include fish, safflower, sunflower, corn, and soybean oils.
- Diabetes. Nutrition is critical to adults with type 2 diabetes. They will have to control portions, eat regularly and eat nutrient-rich foods, along with other dietary guidelines.
- Anemia. People with anemia need to get more iron from their diets and will be encouraged to eat more foods such as soybeans, spinach, and others.
Sometimes, people who are ill need artificial nutrition to help them receive the proper nutrients. The nutrition may come in the form of special drinks that supplement their diets or even be provided through intravenous (IV) injections in a hospital or other facility.
Nutrition is important throughout adults’ lives. As younger adults, good nutrition helps keep people strong as they need energy for active lives that may involve athletic pursuits and busy days filled with work and raising children. Pregnant women will need to pay particular attention to nutrition. In the middle years, proper nutrition helps prevent disease and weight gain that normally is associated with aging and lives that may become more sedentary. And as people reach their mature years, nutrition becomes critical, as many people in their later years fail to eat properly due to medical conditions and medications or social factors.
The United States Department of Agriculture (USDA) and the United States Department of Health and Human Services revised the Dietary Guidelinesfor Americans in 2005. The guidelines are science-based and outline advice for choosing a nutritious diet and maintaining a healthy weight. The 2005 guidelines also address physical activity and food safety and make recommendations for special population groups.
Finally, calorie requirements and servings are based more on gender, age, and level of physical activity, while in 2000, the servings were more uniform for all adults. The USDA also revised the traditional food pyramid to make it customized for individuals.
Basic food groups
The following are the basic food groups included in the pyramid provided by the USDA:
- Grains. The guidelines recommend eating at least three ounces of whole grain bread, cereal, crackers, rice, or pasta every day. At least one-half of all grains should be whole grains, which can be determined by looking for the word “whole” before the grain name on the list of ingredients.
- Vegetables. The pyramid recommends eating more dark green and orange vegetables, as well as more dry beans and peas.
- Fruits. A variety of fresh, frozen, or canned fruit is good, but the USDA recommends taking it easy on fruit juices.
- Milk, yogurt, and cheeses. The USDA recommends getting plenty of calcium-rich food from low-fat or fat-free milk. People who can’t drink milk should turn to lactose-free products or other sources of calcium, such as hard cheeses and yogurt.
- Meat and beans. Lean protein should come from low-fat or lean meats and poultry that is prepared by grilling, baking, or broiling. Varying choices is recommended, so that more fish, beans, peas, nuts, and seeds that provide protein are part of the diet.
- Oils and fats. Most fat sources should come from fish, nuts, and vegetable oils. Solid fats such as butter, stick margarine, shortening, and lard should be limited.
FOOD GROUPS TO ENCOURAGE. The new guidelines encourage eating enough fruits and vegetables to stay within energy needs. Two cups of fruit and about 2 and one-half cups of vegetables per day are adequate for a person consuming 2,000 calories per day. Those eating more or less than 2,000 calories can adjust their fruits and vegetables up or down.
FOOD GROUPS TO MANAGE CAREFULLY. Total fat should be between 20% and 35% of calories and most fat should come from polyunsaturated and monounsaturated fats . Most people should consume less than about 1 tsp. of salt per day. They also should choose food and beverages with little added sugars or high-calorie sweeteners. Alcohol should be consumed in moderation, about one drink per day for women and two drinks per day for men. Drinking alcohol with meals helps.
Adopting a balanced eating pattern
The Dietary Guidelines recommend adopting a balanced eating pattern. Using the USDA’s pyramid can help customize a plan or adults can choose the DASH eating plan. DASH is a plan that was created to help prevent high blood pressure by minimizing salt in the diet, by providing a balance of nutrients, and by keeping weight down.
Recommendations for specific adult populations
Not every adult has the same nutritional needs. In addition to specific nutritional needs related to diseases or activity, the following recommendations apply to certain groups:
- People over age 50. Guidelines recommend consuming vitamin B12 in fortified foods or supplements. -Women of childbearing age. If a woman many become pregnant, she should eat iron-rich plant foods or those that help absorb iron, such as vitamin-C rich foods. Women in their first trimester of pregnancy should consume adequate synthetic folic acid daily from fortified foods or supplements in addition to food forms from a varied diet.
- Older adults, people with dark skin, and people not exposed to sufficient sunlight. These individuals should consume extra vitamin D from vitamin-D fortified foods and/or from supplements.
Getting adequate nutrients
The actual amount of any nutrient a person needs, as well as the amount each individual gets from his or her diet will vary. Many adults do not receive enough calcium from their diets, which can lead to osteoporosis later in life. Other nutrients of concern are potassium, fiber, magnesium, and vitamin E. Some population groups also need to get more vitamin B12, iron , folic acid, and vitamin D. These nutrients should come from food when possible, then from supplements if necessary.
Many adults ignore the role that fluids play in nutrition. It is important to moderate drinking of high-sugar beverages and fruit juices, as well as alcoholic beverages. Most people will get adequate hydration from normal thirst and drinking behavior, especially by consuming fluids with meals.
Nutrition for strength
Adults who are physically active and who strength train or pursue athletic activities will have different nutrition needs than typical adults of the same age. For example, they will require more fluids while exercising. In general, athletes and those who are very active also require more carbohydrates in their diets than typical Americans. Carbohydrates provide energy, but they should come from whole grains and fruits, not from refined sugars.
Vegetarians can achieve recommended nutrient intakes by carefully choosing foods from the basic food groups. They will need to pay special attention to intake of protein , iron, and other vitamins, depending on the type of vegetarian program they follow. Choosing nuts, seeds, and legumes from the meat and beans group, as well as eggs if they desire, can provide enough nutrients at the proper serving level.
Processed and prepared foods
Americans are eating out more than ever and are buying foods in the grocery store that are prepackaged. It is more difficult to judge the nutrients and calories in many of these foods and in general, fresh foods are healthier than those that are packaged. Highly processed foods do not contain significant amounts of essential minerals. They often contain high amounts of fats and sugar, as well as artificial preservatives and other additives. Many restaurants, including fast food restaurants, are trying to offer healthier selections. The USDA offers tips for eating out to help people stay within their healthy pyramid servings and portions.
Calories and weight management
The new guidelines and pyramid focus back on the basics of calorie management. It’s all about balancing energy, or the amount of calories eaten vs. the amount of calories used by the body. By managing portions, eating a balanced diet from the food groups and not using discretionary calories on high-sugar or high-fat foods, people can maintain a reasonable intake of calories. Regular physical activity can help use calories to provide better balance. Research has shown that subtracting just 100 calories a day from the diet can help manage weight, and eating 500 fewer calories a day can result in losing one pound per week in weight. But every individual is different and it is recommended to involve a physician or dietician in a weight loss plan.
Though supplementation of nutrients sometimes is necessary, physicians and dieticians recommend that nutrients come from food, not from vitamins and supplements. Excessive use of vitamins and mineral supplements can lead to serious health problems and it is best to involve a physician to ensure that supplements are being used at appropriate and safe levels. It also is best not to change a diet without the advice of a nutritional expert or health care professional. People who are chronically ill, and women who are pregnant or breastfeeding only should change their diets under professional supervision.
The recommendations in the Dietary Guidelines are for Americans over two years of age.
Duyff, Roberta Larson. ADA Complete Food and Nutrition Guide. Chicago, IL: American Dietetic Association, 2006.
Dietary Guidelines for Americans 2005.Washington, D.C.: U.S. Department of Health and Human Services, U.S. Department of Agriculture, 2005.
American Dietetic Association. 120 South Riverside Plaza, Suite 2000. Chicago, IL 60605. (800) 877-1600. <http://www.eatright.org>
U.S. Department of Agriculture. 1400 Independence Ave. SW, Washington, D.C. 20250. (800) 687-2258. <http://www.cnpp.usda.gov>
Teresa G. Odle