DIET AND BREAST CANCER

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Breast cancer is a disease characterized by fear: fear of pain, disfigurement, and death itself. It is fear grounded in alarming statistics. Last year 175,000 new cases of breast cancer were expected to be diagnosed in the United States, and nearly 45,000 American women died of the disease ( 1).

Better screening techniques, such as mammography, have resulted in earlier detection and treatment for many women. But can a woman actually reduce her chance of getting breast cancer?

Some researchers now believe that by making some simple dietary and lifestyle changes, women can decrease their risk of breast cancer. This article will look at some of the suspected risk factors for the disease, and outline some of the specific dietary guidelines (especially those relevant to vegetarians) which have been developed to help women reduce their risk of breast cancer.

CAUSES OF BREAST CANCER

The causes of breast cancer are complex. The disease is known to begin as the mutation of a single cell, as a result of exposure to an agent that can cause cancer ( 2). After a cell has mutated, it is likely that many "risk factors" act together to cause the growth of cancer ( 2).

Established Risk Factors: Established risk factors are those known to increase risk for the development of the disease. The established risk factors for breast cancer are age, reproductive history, and family history ( 2).

Age: As a woman ages, her risk of breast cancer rises steadily ( 3, 4), with the highest rates seen after menopause ( 4).

Reproductive History: Childbearing appears to be protective against breast cancer. Women who never bear children have higher rates of breast cancer than women who bear at least one child. Breastfeeding also appears to reduce risk for the disease ( 5).

Family History: Women whose mothers or sisters have had breast cancer are at higher risk themselves ( 2).

Suspected Risk Factors: Suspected risk factors are agents or influences which may play a role in the development of the disease, but which require further study. The suspected risk factors for breast cancer include oral contraceptive use, obesity, and diet.

Oral Contraceptives: Some studies have shown an increased risk of breast cancer among women who took oral contraceptives; others have shown no effect at all ( 6).

Obesity: Higher rates of breast cancer have been seen in obese women ( 7).

Diet: During the past ten years, great attention has been given to the role of dietary factors, such as fat, fiber, and protein intake, in the development of breast cancer. Many studies have looked at both the independent and combined effects of these nutrients in promoting the development of breast cancer.

Breast cancer rates within specific populations are also affected by dietary factors. Between 1955 and 1975, deaths from breast cancer in Japan doubled in women aged forty-five to fifty-nine ( 10). Researchers found that those women who ate a high-fat diet (defined as dally meat consumption) during this period had death rates from breast cancer two times higher than women eating an apparently low-fat diet ( 10). In addition, first generation Japanese women who migrate to the United States have rates of breast cancer three times higher than those of Japanese women living in Japan, suggesting the powerful influence of environmental factors such as diet ( 11).

Studies of groups of women with breast cancer have also shed light on the role dietary fat may play in promoting breast cancer. Rates of breast cancer appear to be 2-3 times higher among women who eat a diet rich in fat (defined as frequent or daily consumption of meat and/or whole milk), compared to women who abstain from these foods, or eat them less frequently ( 8, 10, 12, 13).

The role of dietary fat in development of breast cancer has recently been questioned. A very large study of American nurses failed to find any link between fat Intake and risk of breast cancer ( 14). The women who participated in this study consumed an average of 30 percent of their calories from fat. Perhaps to significantly reduce breast cancer, fat consumption needs to be below 30 percent of total calories. This would mean that American women, who consume 35 to 40 percent of their calories from fat, would need to make some major dietary changes (i.e., reduce their total fat intake to well below 30 percent of total calories) to decrease their cancer risk. (See Appendix for Guidelines for Fat Reduction.)

Although a link has been seen in some studies between a high-fat diet and increased risk of breast cancer, less is known about the link between specific types of fat and breast cancer. Is saturated or unsaturated fat the culprit, or is the amount of total fat the most important factor? A recent combined analysis of breast cancer studies examined rates of the disease among 10,522 women in eight countries. Researchers determined that the risk of breast cancer was greatest in older women who reported eating the largest amount of saturated fat; the risk of cancer also rose as the level of total fat in the diet rose ( 15). This study supports limiting both saturated and total fat.

OTHER DIETARY FACTORS

The link between protein intake and risk of breast cancer is much weaker than the relationship between fat intake and breast cancer ( 8). The greater risk of breast cancer among meat eaters seems to be due mainly to fat intake, and not protein consumption ( 8, 10).

The risk of breast cancer appears to be lower when a diet rich in dark green and deep yellow vegetables (particularly carrots) is eaten ( 8, 12, 16). In addition, the consumption of fiber-rich foods and of food high in vitamin A appears to lower the risk of breast cancer ( 8).

An increased risk of breast cancer has been seen among women who use moderate amounts of alcohol (1 to 3 drinks per clay) ( 17, 18, 19). However, caffeine consumption has not been found to increase the risk of breast cancer ( 20).

VEGETARIAN DIETS

Very few studies have looked at breast cancer incidence among vegetarians, and results of existing studies have been inconclusive. For example, British researchers found no difference in the rates of breast cancer between nuns eating a vegetarian diet, and single non-vegetarian British women ( 21). Furthermore, Seventh-day Adventists, consuming minimal amounts of meat, did not have significantly lower rates of breast cancer ( 22). However, the average total fat intake (36 percent) of Seventh-day Adventists in this study was similar to that of the general population in the United States, suggesting that the amount of fat in the diet is at least as important as the type of fat (animal vs. plant fat) ( 22).

These inconclusive findings do not mean that a vegetarian diet is not protective against breast cancer. Dietary modifications to reduce fat and increase fiber Intake appear to reduce the risk of breast cancer. For some, these modifications may be easier to achieve on a vegetarian diet.

CONCLUSIONS AND RECOMMENDATIONS

The preceding suggests that a diet high in fat and low in fiber may be a risk factor for breast cancer. In addition, a diet rich in beta-carotene and/or vitamin A may offer protection against the disease.

What specific steps can a woman take to reduce her risk of breast cancer?

The following dietary guidelines, consistent with the recommendations offered by the Committee on Diet and Health of the National Research Council, may be helpful in reducing the risk of breast cancer ( 8):

1. Reduce total fat intake to less than 30 percent of total calories.
2. Reduce saturated fat to less than 10 percent of total calories.
3. Increase intake of foods rich in beta-carotene.
4. Increase intake of fiber-rich foods.
5. Maintain ideal body weight.
6. Limit intake of alcohol to no more than 1 ounce of pure alcohol daily (1 ounce pure alcohol = two 12-ounce beers, 8 ounces of wine, or 2 "mixed drinks").

With a little planning, a vegetarian can easily meet these guidelines. Meat, whole-milk dairy products, butter, and traditional "fast foods" are major sources of total and saturated fat in the American diet. By avoiding these foods, using low-fat cooking methods (steaming or baking), and seasoning foods with herbs, lemon juice, soy sauce, and/or vinegars instead of margarine or oils, vegetarians can markedly reduce their intake of fat and saturated fat.

Choose a variety of fruits and vegetables, including those that are good sources of beta carotene (carrots, broccoli, spinach, winter squash, sweet potatoes, cantaloupe, etc.), and those that are good sources of fiber (apples, corn, peas, cabbage, etc.). The Committee on Diet and Health suggests eating at least five 1/2-cup servings of fruit and vegetables each day, concentrating on the deep green and yellow vegetables, and the citrus fruits ( 8).

In planning a high-fiber, low-fat diet, one of the most beneficial foods to include is legumes. Lentils, peas, and beans provide delicious, inexpensive sources of protein, with virtually no fat. These foods are also good sources of vitamins, iron, and zinc.

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SAMPLE MENU

The following menu is based on the dietary guidelines suggested above. It provides about 2000 calries, and is approximately 62 percent carbohydrate, 14 percent protein, 24 percent total fat, and 5 percent saturated fat. Those who are watching their weight, or have smaller appetites, can reduce their intake to about 1500 calories by cutting the amounts of cooking oil and salad dressing in half, and by skipping the rice at lunch and the dessert at dinner.

BREAKFAST

1. 2 Cup oatmeal with 1/2 Cup skim or soy milk
2. Cup cantaloupe
3. Cup orange juice

LUNCH

1. medium bean burrito (no cheese)
2. 2 Cup Spanish rice

lemonade

SNACK

1. 2 Cup fresh pineapple
2. Cup non-fat yogurt

DINNER

1. Cup tofu stir-fried in 1 TB oil with
2. 1/2 Cups broccoli, zucchini, and scallions
3. medium baked potato with 1 tsp. tahini

Tossed salad with 2 TB oil and vinegar dressing

Baked apple with cinnamon

Cranberry juice

HOW TO KEEP FAT INTAKE BELOW 30 PERCENT

The American diet is about 37 percent fat. To reduce risk of cancer and heart disease, it is recommended that fat intake be kept below 30 percent of total calories. The "typical" American man eats about 2000 calories per day, while the "typical" American woman eats about 1600 calories daily. Based on these estimates, a man eating 2000 calories should consume no more than about 67 grams of fat per day, while a woman eating 1600 calories should take in no more than 53 grams of fat per day.
REFERENCES

(1.) Cancer Facts and Figure - 1991. American Cancer Society, 1991.

(2.) Petrakis NL, Ernster VL, King MC. "Breast Cancer." In: Schottenfeld D, Fraumeni JF, eds. Cancer Epidemiology and Prevention. Philadelphia: W. B. Saunders, 1982: 855-70.

(3.) Devitt JE. "The influence of age on the behavior of carcinoma of the breast." Can Med Assoc J 1970; 103:923-931.

(4.) Pfeiffer CH, Mulliken JB. Caring for the Patient with Breast Cancer: An Interdisciplinary and Multidisciplinary Approach. Reston, Virginia: Reston Publishing Co., Inc., 1984: 2-5.

(5.) Macmahon B, Purde M, Cramar D, Hunt E. "Association of breast cancer risk with age at first and subsequent births -- a study in the population of the Estonian republic." JNCI 1982; 69: 1035-38.

(6.) Baum M. Breast Cancer: The Facts. New York: Oxford University Press, 1981; 1-4.

(7.) Verreault R, Brisson J, et al. "Body weight and prognostic indicators in breast cancer." Am J Epidemiol 1989; 129: 260- 68.

(8.) Diet and Health: Implications for Reducing Chronic Disease Risk. Committee on Diet and Health, National Research Council, National Academy of Sciences, Washington, D.C., 1989; 12-17 and 205-208.

(9.) Diet, Nutrition, and Prevention of Chronic Diseases: Report of a WHO Study Group. World Health Organization, Geneva,1970; 65-68.

(10.) Hirayama T. "Epidemiology of breast cancer with special reference to the role of diet." Prev Med 1978; 7: 173-95.

(11.) The Breast Cancer Digest. A guide to medical care, emotional support, educational program, and resources. Office of Cancer Communications, National Cancer Institute, Maryland, 1979; 3-8.

(12.) LaVecchia C, Decarli A, Franchesi S, et al. "Dietary factors and the risk of breast cancer." Nutr Cancer 1987; 10: 206- 14.

(13.) Le MG, Moulton LH, Hill C, et el. "Consumption of dairy products and alcohol in a case-control study of breast cancer." JNCI 1986; 77: 633-36.

(14.) Willett WC, Stampfer G, Colditz B, Rosner CH, Hennekens CH, Speizer FE. "Dietary fat and risk of breast cancer." N Engl J Med 1987; 316: 22-28.

(15.) Howe GR, Hirohata T, Hislop TG, et al. "Dietary factors and risk of breast cancer: combined analysis of 12 case-control studies." JNCI 1990; 82: 561-69.

(16.) Katsouyanni K, Trichopolous D, Boyle P, et al. "Diet and breast cancer: a case-control study in Greece." Int J Cancer 1986; 38: 815-20.

(17.) Schatzkin A, Jones Y, Hoover RN, et al. "Alcohol consumption and breast cancer in the Epidemiologic Follow-up Study of the First National Health and Nutrition Examination Survey." N Engl J Med 1987; 316: 1169-73.

(18.) Hiatt RA, Klatsky AL, Armstrong MA. "Alcohol consumption and the risk of breast cancer in a prepaid health plan." Cancer Res 1988; 48: 2284-87.

(19.) Willett WC, Stampher MJ, Colditz GA, et al. "Moderate alcohol consumption and the risk of breast cancer." N Engl J Med 1987; 316: 1174-80.

(20.) Skegg DC. "Alcohol, coffee, fat, and breast cancer." Br Med J 1987; 295: 1011-12.

(21.) Kinlen LJ. "Meat and fat consumption and cancer mortality: a study of strict religious orders in Britain." Lancet 1982; 1: 946-49.

(22.) Phillips RL, Garfinkel L, Kuzma JW, et al. `Mortality among California Seventh-day Adventists for selected cancer sites." JNCl 1980; 65: 1097-1107.

Article copyright The Vegetarian Resource Group, Inc.

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By Mary Franz

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