Diet Guidelines
ACS Guidelines on Diet, Nutrition, and Cancer Prevention
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Eat five or more servings of fruits and vegetables each day.
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Eat other foods from plant sources, such as breads, cereals, grain products, rice, pasta, or beans several times each day.
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1. Choose most of the foods you eat from plant sources.
Eat five or more servings of fruits and vegetables each day.
- Include fruits or vegetables in every meal.
- Choose fruits and vegetables for snacks.
- Eat other foods from plant sources, such as breads, cereals, grain products, rice, pasta, or beans several times each day.
- Include grain products in every meal.
- Choose whole grains in preference to processed (refined) grains.
- Choose beans as an alternative to meat.
The scientific basis for these recommendations is very strong for cancers at many sites, particularly for cancers of the gastrointestinal and respiratory tracts. 15-18 The evidence is particularly strong that increased consumption of fruits and vegetables reduces the risk of colon cancer.19, 3 Of the many scientific studies on this subject, the great majority show that eating fruits and vegetables (especially green and dark yellow vegetables and those in the cabbage family, soy products, and legumes) protects against colon cancer. Evidence is less strong for cancers considered hormonal, such as breast and prostate.
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Greater consumption of vegetables, fruits, or both together has also been associated with a lower risk of lung cancer.20, 21 The major risk factor for lung cancer is tobacco, but diet also affects risk. Studies have shown that people who smoke cigarettes tend to eat less healthful diets than nonsmokers, but fruits and vegetables reduce cancer risk whether or not people smoke. Because many studies indicate that foods high in beta carotene protect against lung cancer, scientists have suggested that beta carotene itself might reduce lung cancer risk. Recent clinical trials of beta carotene supplements, however, have shown that smokers taking the supplement developed lung cancer at higher rates than those taking a placebo.22, 23 These findings support the idea that beta carotene may be a proxy for other protective nutrients or substances, singly or in combination, within foods. They also suggest that taking a single nutrient in large amounts may produce adverse effects.
Despite the strength of the evidence associating consumption of fruits and vegetables with decreased cancer risk, intake of these foods is low among many adults and children.24, 25 Concern about low intake levels has led to a countrywide initiative—the National 5 A Day for Better Health Program—to increase fruit and vegetable intake to five or more servings of fruits and vegetables daily.26 This recommendation applies to foods in their fresh, frozen, canned, dried, or juice forms, but does not apply to specific nutrients or other substances that might be extracted from them. Vegetables and fruits are complex foods containing more than 100 beneficial vitamins, minerals, fiber, and other substances. Scientists do not yet know which of the nutrients or other substances in fruits and vegetables may be protective against cancer. The principal possibilities include specific vitamins and minerals, fiber, and phytochemicals—carotenoids, flavonoids, terpenes, sterols, indoles, and phenols—that are present in foods of plant origin.15,17 How fruits and vegetables exert their protective effects constitutes an active area of scientific inquiry. Until more is known about specific food components, the best advice is to eat 5 or more servings of fruits and vegetables each day.
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Grains such as wheat, rice, oats, barley, and the foods made from them constitute the base of healthful diets as illustrated in the USDA Food Guide Pyramid.9 Healthful diets contain 6 to 11 standard servings of foods from this group each day. As shown in Table 2, standard portion sizes are defined as quite small, and this number of servings is not difficult to achieve. Grains are an important source of many vitamins and minerals such as folate, calcium, and selenium, all of which have been associated with a lower risk of colon cancer.19 Whole grains are higher in fiber and certain vitamins and minerals than refined flour products. Since the benefits of grain foods may derive from their other nutrients as well as from fiber,27 it is best to obtain fiber from fruits, vegetables, and whole grains rather than from fiber supplements.
Beans are excellent sources of many vitamins and minerals, protein, and fiber. Beans are legumes, the technical term for the family of plants that includes dried beans, pinto beans, lentils, and soybeans, among many others. Beans are especially rich in nutrients that may protect against cancer,8 and can be a useful low-fat but high-protein alternative to meat.
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2. Limit your intake of high-fat foods, particularly from animal sources.
Choose foods low in fat.
- Replace fat-rich foods with fruits, vegetables, grains, and beans.
- Eat smaller portions of high-fat foods.
- Choose baked and broiled foods instead of fried foods.
- Select non-fat and low-fat milk and dairy products.
- When you eat packaged, snack, convenience, and restaurant foods, choose those low in fat.
Limit consumption of meats, especially high-fat meats.
- When you eat meat, select lean cuts.
- Eat smaller portions of meats.
- Choose beans, seafood, and poultry as an alternative to beef, pork, and lamb.
- Select baked and broiled meats, seafood, and poultry, rather than fried.
High-fat diets have been associated with an increase in the risk of cancers of the colon and rectum,19 prostate,29 and endometrium.30 The association between high-fat diets and breast cancer is much weaker.31, 32 Whether these associations are due to the total amount of fat, the particular type of fat (saturated, monounsaturated, or polyunsaturated), the calories contributed by fat, or some other factor in the fats in food has not yet been determined. Because a gram of fat contains more than twice the calories of a gram of protein or carbohydrate (9 versus 4 kcal/gram), studies cannot easily distinguish the effects of fat itself from effects of the calories it contains. Moreover, people who eat high-fat diets tend to be heavier and to eat more meat and fewer fruits and vegetables, so their risk of cancer also is increased for other reasons.
What Counts as a Serving?*
Fruits
1 medium apple, banana, orange
1/2 cup of chopped, cooked, or canned fruit
3/4 cup of fruit juice
Vegetables
1 cup of raw leafy vegetables
1/2 cup of other cooked or raw vegetables, chopped
3/4 cup vegetables juice
Grains
1 slice bread
1 ounce ready-to-eat cereal
1/2 cup of cooked cereal, rice pasta
Beans and nuts
1/2 cup cooked dry beans
2 tablespoons peanut butter
1/3 cup nuts
Dairy foods and eggs
1 cup milk or yogurt
1 1/2 ounces of natural cheese
2 ounces processed cheese
1 egg
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Meats
2-3 ounces of cooked lean meat, poultry, fish
*Source: US Department of Agriculture and US Department of Health and Human Services. Nutrition and Your Health: Dietary Guidelines for Americans, 4th ed. Home and Garden Bull 232. Washington, DC: Government Printing Office, 1995.
Foods from animal sources remain major contributors of total fat, saturated fat, and cholesterol in the American diet.33 Although meats are good sources of high-quality protein and supply many important vitamins and minerals, consumption of meat—specially red meats (beef, pork, lamb)—has been linked to cancers at several sites, most notably colon and prostate.34 How much of the association between red meats and cancer is due to total fat or saturated fat, and how much is due to other constituents of meat or the diet is uncertain at present.19, 29, 30 For example, in addition to fat, mutagenic compounds such as heterocyclic amines, which are produced when protein is cooked at high temperature, may help explain the association between meat and colon cancer. Saturated, monounsaturated, and polyunsaturated fats all yield the same number of calories, but may affect cancer risk in different ways. Even the effects of specific fats, such as those from vegetable or fish oils, may differ in their effects on cancer risk. This relationship of types of fat to cancer risk is under active investigation.35
Much evidence indicates that saturated fat may be particularly important in increasing risk for cancer as well as for heart disease. The best way to reduce saturated fat intake is to make wise choices in the selection and preparation of animal foods. Choose lean meats and lower-fat dairy products, and substitute vegetable oils for butter or lard. Food labels can be a useful guide to choosing packaged foods lower in saturated fat. Choose smaller portions and use meat as a side dish rather than as the focus of a meal. Emphasize beans, grains, and vegetables in meals to help shift dietary patterns to include more foods from plant rather than animal sources. Preparation methods are also important; baking and broiling foods, rather than frying them, reduces the over-all amount of fat in food. These recommendations for cancer prevention are consistent with dietary advice to reduce cardiovascular disease risk.10-13, 36
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3. Be physically active: achieve and maintain a healthy weight.
Be at least moderately active for 30 minutes or more on most days of the week. Stay within your healthy weight range.
Physical activity can help protect against some cancers, either by balancing caloric intake with energy expenditure or by other mechanisms. An imbalance of caloric intake and output can lead to over-weight, obesity, and increased risk for cancers at several sites: colon and rectum,19 prostate,29 endometrium,30 breast (among postmenopausal women),31 and kidney.37
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These findings are supported by animal studies, and by epidemiologic studies demonstrating an association between physical activity and a reduced risk of developing some cancers.38 Activity simply may prevent obesity or it may act in other ways to reduce cancer risk. For breast and prostate cancer, physical activity may act through effects on hormone levels.39, 40 For colon cancer, physical activity stimulates movement through the bowel, thereby reducing the length of time that the bowel lining is exposed to mutagens.
Both physical activity and controlled caloric intake are necessary to achieve or to maintain a healthy body weight.41 Maintaining a body weight within recommended ranges helps to reduce the risk for chronic diseases such as coronary heart disease and diabetes as well as cancer. Moderate physical activity may increase caloric needs and encourage the consumption of more healthful foods—especially fruits, vegetables, grains, and beans—while maintaining a recommended body weight.
The Centers for Disease Control and Prevention and the American College of Sports Medicine,42 a National Institutes of Health Consensus Conference,43 and the US Surgeon General 44 recommend 30 minutes of moderate physical activity each day as a means to promote health. The 30 minutes does not need to be continuous to be beneficial, and can be accomplished by walking briskly (3-4 miles per hour) for about 2 miles, or by a variety of other enjoyable activities including calisthenics, jogging, swimming, gardening, yard work, housework, and dancing at a level of intensity equivalent to brisk walking. Studies suggest that when overweight people intentionally lose weight, they reduce their cancer risk.45 To lose weight, restrict caloric intake and increase physical activity. The easiest way to restrict calories is to limit serving sizes, particularly of high-fat foods (Table 2). It is important to recognize, however, that many fat-free cakes, cookies, snack foods, and frozen and other desserts remain high in calories.
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4. Limit consumption of alcoholic beverages, if you drink at all.
Alcohol consumption increases the risk of cancers of the mouth, esophagus, pharynx, larynx, and liver in men and women, and of breast cancer in women.46, 47 Cancer risk increases with the amount of alcohol consumed. For cancers of the mouth, esophagus, and larynx, risk increases substantially with intake of more than two drinks per day. A drink of alcohol is defined as 12 ounces of regular beer, 5 ounces of wine, or 1.5 ounces of 80-proof distilled spirits.48-50 The combined use of alcohol and tobacco greatly increases the risk of these cancers compared to drinking or smoking alone.5
Many studies also have reported an increased risk of breast cancer in women who drink alcohol.5 The mechanism is unknown but may be due to alcohol-induced changes in hormones in the blood,51 or to a carcinogenic effect of alcohol or its metabolites on breast tissue.46
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Alcohol may have additional effects on cancer risk. Alcoholic beverages supply calories but few nutrients; people who drink heavily may be substituting alcohol for nutrient-rich, cancer-protective foods. Regardless of the mechanism, studies show that the risk of breast cancer increases with an intake beginning at just a few drinks per week.31, 52 Reducing alcohol consumption is a good way for women who drink regularly to reduce their risk of breast cancer.
Moderate intake of alcoholic beverages has been shown to decrease the risk of coronary heart disease and stroke.53 The cardiovascular benefits of moderate drinking usually outweigh the risk of cancer in men over age 50 and in women over age 60. 53 Public health officials advise people who already drink alcoholic beverages to limit their intake to two drinks a day for men, and one drink per day for women.10 Women generally tolerate alcohol less well than men as a result of smaller body size and greater ability to absorb alcohol. Women with an unusually high risk for breast cancer might reasonably consider abstaining from alcohol. Children and adolescents, pregnant women, people taking medications affected by alcohol, and those who are driving, operating machinery, or unable to limit themselves to moderate drinking should abstain from alcohol.
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