A High-Fiber Defense Against Breast Cancer

October is National Breast Cancer Awareness Month. Today, a look at breast cancer and diet.

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Most of us who treat breast cancer emphasize early detection through mammography, breast self-examination and exams done by a trained physician. But what a patient usually asks is, “Can I prevent breast cancer or at least lower my chances of developing it?”

The answer is a definite maybe.

A woman cannot change her genes, family history or age, but she can certainly alter her diet.

The significant correlation between breast cancer and diet is supported by epidemiological studies comparing diet and breast cancer rates among different cultures and nations.

For example, women in Japan who eat a traditional Japanese diet have a relatively low rate of breast cancer. But when their diet changes, the breast cancer rate increases.

Studying diet intake and breast cancer rates among women of different countries reveals that dietary fat correlates strongly with an increase in breast cancer.

When women from countries with low breast cancer rates migrate to the United States, their chances of developing breast cancer increases. And after one or two generations, their daughters have rates that match those normally seen in the United States.

The National Cancer Institute estimates that at least 35% of all cancers are associated with nutrition. What we eat can make a difference in our energy levels, our mood, even our self-esteem. Studies suggest an association between high cancer rates and a diet high in saturated fat and animal protein.

On the other hand, dietary fiber (found only in plants) seems to protect against some cancers, including breast cancer. The typical American woman has a diet with very little fiber.

There is a vast amount of experimental evidence strongly supporting the theory that dietary fat, independent of caloric intake, has a major impact on the incidence and mortality of breast cancer.

One reason fat may promote breast cancer is that fat cells are one place where estrogen is altered in the body. Estrogen is the female hormone that can make breast cancer cells grow faster. In addition, there are sound experimental studies showing that fat helps tumors spread. Dietary fat may turn on genes allowing cancer cells to spread, or perhaps reduce the ability of the immune system to kill cancer cells, and even increase hormones stimulating cancer cells.

Besides being low in fat, high-fiber diets contain antioxidants and other protective compounds that may help to lower estrogen levels and protect against cancer in other ways. The antioxidants--like vitamins A, C and E found in fruits and vegetables--may be important inhibitors of cancer formation.

Soybeans also offer protection against breast cancer. Compounds found in soy, called isoflavones, are like weak estrogens. They bind to estrogen receptors in the breast, preventing the stronger, potentially harmful estrogens from binding.

Limiting consumption of alcoholic beverages is another possible way to curb the occurrence of breast cancer. Cancer risk increases with the amount of alcohol consumed and may start to rise with intake as little as two or three drinks per day. The exact mechanism of this increased risk is not well understood, but may be due to the carcinogenic actions of alcohol or its metabolites, alcohol-induced changes in levels of estrogen, or to some other unknown processes.

While there is good suggestive evidence that breast cancer can be affected by diet, no study has been done to directly examine the effects of altering the diet.

The Women’s Intervention Nutrition Study (WINS), sponsored by the National Cancer Institute of the National Institutes of Health, is a major nationwide trial investigating the effects of dietary fat on the incidence of recurrence and survival in women with early-stage breast cancer. Patients participate in a controlled low-fat, high-fiber diet to see if breast cancer recurrence can be reduced.

“Although we need more research to arrive at the final verdict on the perfect diet to fight breast cancer, there is absolutely no reason for women to wait for that day to arrive,” says Rachel Beller, a registered dietitian and coordinator for the study at John Wayne Cancer Institute.

“The WINS study is a potentially important study that will answer nutritional questions to help women with breast cancer live longer, healthier, happier lives,” Beller says.

Of course, eating right helps prevent a host of other diet-related diseases, such as coronary artery disease and obesity. And someday, thanks to the women who participate in trials like the WINS study, we will know more about diet and breast cancer prevention.

* Giuliano is chief of surgical oncology at the Joyce Eisenberg Keefer Breast Center at the John Wayne Cancer Institute at St. John’s Hospital, Santa Monica.

* Next week: How to examine your breasts.