Diet and health

Patient information: Diet and health

Author
Graham A Colditz, MD, DrPH Section Editor
Timothy O Lipman, MD Deputy Editor
Leah K Moynihan, RNC, MSN
David M Rind, MD

HEALTHY DIET OVERVIEW — The food choices we make can have an important impact on our health. However, expert opinions about which and how much of these foods is best continues to change as new research is completed.

This topic summarizes the research about the relationships between various foods or supplements and specific health conditions, and concludes with general recommendations for following a healthy diet. A separate topic review is available about diets for weight loss. (See “Patient information: Weight loss treatments”, section on Diet therapy).

FRUITS AND VEGETABLES — A number of studies have demonstrated important health benefits of eating fruits and vegetables.

These foods decrease the risk of cardiovascular diseases including coronary heart disease (CHD) and stroke [1] ; eating up to six servings per day appears to provide the most benefit. Cruciferous vegetables (ie, broccoli, cabbage, cauliflower, brussel sprouts), green leafy vegetables, citrus fruits, and vitamin C-rich fruit and vegetables may lower the risk of cardiovascular disease to the greatest extent.
High intake of fruits and vegetables also reduces the risk of developing certain kinds of cancer (including lung cancer and cancer of the gastrointestinal system). As an example, it is estimated that for every additional serving of fruit and vegetables per day there is a 5 percent reduction in the risk of lung cancer [2] .
The National Cancer Institute recommends a goal of five servings of fruits or vegetables per day.

FIBER — Eating a diet that is high in fiber can decrease the risk of coronary heart disease and stroke by 40 to 50 percent [3] . Eating fiber also protects against type 2 diabetes, and eating soluble fiber (such as that found in vegetables, fruits, and especially legumes) may help control blood sugar in people who already have diabetes. (See “Patient information: High fiber diet”).

The recommended amount of dietary fiber is 20 to 35 grams of fiber per day. Many breakfast cereals are excellent sources of dietary fiber. By reading the product information panel on the side of the package, it is possible to determine the number of grams of fiber per serving (show figure 2). A list of the fiber content of a number of foods can be found in the following table. (show table 1A-1C).

FAT — High blood cholesterol levels increase the risk of coronary heart disease. Eating foods lower in certain types of fat and cutting back on foods that contain cholesterol can lower cholesterol levels and reduce the risk of coronary heart disease. (See “Patient information: High cholesterol and lipids (hyperlipidemia)”).

The type of fat consumed appears to be more important than the amount of total fat (show table 2 and show table 3). Saturated fats and trans fats should be avoided.

Trans fats are those that are solid at room temperature, and are found in many margarines and in other fats labeled “partially hydrogenated.” Another major source is oils that are maintained at high temperature for a long period. such as in fast food restaurants.
Saturated fats come mainly from animal products, such as cheese, butter, and red meat.
When considering a low fat diet, it is important not to replace fat with carbohydrates. Increases in carbohydrate intake may lower levels of high density lipoprotein (HDL) cholesterol (good cholesterol), which actually increases the risk of coronary heart disease.

FOLATE — Folate is a type of B vitamin that is important in the production of red blood cells. Low levels of folate in pregnant women have been linked to a group of birth defects called neural tube defects, which includes spina bifida and anencephaly. Vitamins containing folate and breakfast cereal fortified with folate are recommended as the best ways to ensure adequate folate intake.

However, supplements containing folate (called folic acid) are no longer recommended to reduce the risk of colon cancer or heart disease.

ANTIOXIDANTS — The antioxidant vitamins include vitamins A, C, E, and beta carotene. Many other foods, especially fruits and vegetables, also have antioxidant properties. Studies have not clearly shown that antioxidant vitamins prevent cancer, and some studies show they may actually cause harm.

No recommendations can yet be made regarding the use of vitamin C to prevent coronary heart disease (CHD).

Vitamin E supplements, either alone or in combination with other antioxidant vitamins, are of no benefit in preventing prevention of CHD. Studies have also failed to show that supplements of vitamins E and C decrease the risk of stroke. The American Heart Association does recommend, however, that a healthy diet include foods high in antioxidants, such as fruits, vegetables, and whole grains.

CALCIUM AND VITAMIN D — Adequate calcium and vitamin D intake are important, particularly in women, to reduce the risk of osteoporosis. A health care provider can help to decide if supplements are needed, depending upon a persons’ dietary intake of calcium and vitamin D (show table 4). Calcium from food sources and supplements appears to slightly increase the risk of prostate cancer, although it may help to protect against colon cancer.

Although the optimal level has not been clearly established, experts recommend that premenopausal women and men consume at least 1000 mg per day and postmenopausal women should consume 1500 mg per day. No more than 2000 mg of calcium should be consumed per day. (See “Patient information: Calcium and Vitamin D for bone health”).

Experts recommend that adults consume a total of 800 International Units (IU) of vitamin D each day. This dose appears to reduce bone loss and the number of bone fractures in older women and men. Milk is the primary dietary source of dietary vitamin D, containing approximately 100 IU per cup. Infants and children also need vitamin D. (See “Patient information: Starting solid foods during infancy”).

ALCOHOL — Moderate alcohol intake may reduce the risk of heart disease. However, it is not clear what amount of alcohol is best. There are some risks associated with alcohol use, including breast cancer in women; cancers of the mouth, esophagus, throat, larynx, and liver; other illnesses such as cirrhosis and alcoholism; and injuries and other trauma-related problems, particularly in men. (See “Patient information: Risks and benefits of alcohol”).

Based on the trade-off between these risks and benefits, the United States Dietary Guidelines recommend alcohol intake in moderation, if at all. This means no more than one drink per day for women, and up to 2 drinks per day for men. Drinking is discouraged for those under 40 years who are at low risk of cardiovascular disease because the risks are likely to outweigh the benefits in this group.

CALORIE RECOMMENDATIONS — The total number of calories a person needs depends upon the following factors:

Weight
Age
Gender
Height
Activity level
For example, a 25-year old woman who is 5 feet, 5 inches tall and 140 pounds and is moderately active needs approximately 2100 calories per day to maintain her weight. A woman who is older, shorter, weighs less, or is less active would need fewer calories per day while a woman who is taller, younger, weighs more, or is more active would need more calories per day to maintain her weight.

The American Cancer Society provides a calculator that estimates the number of calories that a person should consume per day based upon their current (or target) weight, gender, and activity level. It is available online at the following web site: www.cancer.org/docroot/PED/content/PED_6_1x_Calorie_Calculator.asp

GENERAL RECOMMENDATION FOR A HEALTHY DIET — Eat a lot of vegetables, fruits, whole grains, and a limited amount of red meat. Eat at least five servings a day of fruits and vegetables. More is even better. Tips for achieving this goal include:

Make fruits and vegetables part of every meal. Frozen or canned products can be used when fresh products are not convenient or unavailable.
Add fruit to cereal.
Eat vegetables as snacks.
Leave a bowl of fruit out all the time for adults and children to eat as snacks
Trans fats and saturated fats should be avoided (show table 2 and show table 3). Monounsaturated and polyunsaturated fats should be used instead. Tips to accomplish this include:

Choose chicken, fish, or beans instead of red meat and cheese.
Cook with oils that contain a lot of polyunsaturated and monounsaturated fats, like olive and canola oil.
Choose margarines that do not have partially hydrogenated oils. Soft margarines (especially squeeze margarines) have less trans fats than stick margarines.
Eat fewer store-bought baked goods that may contain partially hydrogenated fats, such as crackers, cookies, and cupcakes.
When eating at fast food restaurants, choose items like broiled chicken.
Get enough folate every day (400 micrograms per day). Tips for achieving this goal include:

Take a daily multivitamin containing 400 micrograms of folate. This is especially important for women in the childbearing years.
Eat breakfast cereal that is fortified with folate.
Eat fruits and vegetables that are rich in folate, like oranges, orange juice, and green leafy vegetables.
Avoid excessive alcohol intake. Tips for achieving this goal include:

Choose non-alcoholic beverages, like juices and sodas, at meals and parties.
Avoid occasions centered around alcohol.
Avoid making alcohol an essential part of family gatherings.
WHERE TO GET MORE INFORMATION — Your healthcare provider is the best source of information for questions and concerns related to your medical problem. Because no two people are exactly alike and recommendations can vary from one person to another, it is important to seek guidance from a provider who is familiar with your individual situation.

This discussion will be updated as needed every four months on our web site (www.uptodate.com/patients). Additional topics as well as selected discussions written for healthcare professionals are also available for those who would like more detailed information.

A number of web sites have information about medical problems and treatments, although it can be difficult to know which sites are reputable. Information provided by the National Institutes of Health, national medical societies and some other well-established organizations are often reliable sources of information, although the frequency with which they are updated is variable.

National Library of Medicine
(www.nlm.nih.gov/medlineplus/healthtopics.html)

Harvard Center for Cancer Prevention
(www.yourcancerrisk.harvard.edu)

The Hormone Foundation
(www.hormone.org)

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REFERENCES

1 Joshipura, KJ, Hu, FB, Manson, JE, et al. The effect of fruit and vegetable intake on risk for coronary heart disease. Ann Intern Med 2001; 134:1106.
2 World Cancer Research Fund, American Institute for Cancer Research. Food, Nutrition and the Prevention of Cancer: A Global Perspective. American Institute for Cancer Research, Washington, DC 1997.
3 Wolk, A, Manson, JE, Stampfer, MJ, et al. Long-term intake of dietary fiber and decreased risk of coronary heart disease among women. JAMA 1999; 281:1998.
4 Negri, E, Franceschi, S, Parpinel, M, La Vecchia, C. Fiber intake and risk of colorectal cancer. Cancer Epidemiol Biomarkers Prev 1998; 7:667.
5 Hu, FB, Stampfer, MJ, Manson, JE, et al. Dietary fat intake and the risk of coronary heart disease in women. N Engl J Med 1997; 337:1491.
6 Ascherio, A, Rimm, EB, Giovannucci, EL, et al. Dietary fat and risk of coronary heart disease in men: Cohort follow up study in the United States. BMJ 1996; 313:84.

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