Can Diet Prevent It - Risk Factors: Breast Cancer

Content provided by the Faculty of the Harvard Medical School

Can diet prevent it?

The connection between diet and breast cancer has been carefully studied, but research has not found a strong link between breast cancer and any foods, vitamins, or nutrients. Of all the nutrients studied, folic acid appears to be the most protective. But these are early findings. Research on a variety of foods and nutrients is ongoing.

Based on what we know now, cancer experts recommend a basic, healthy diet that is high in fruits and vegetables and low in saturated fats.

Dietary fat. Research has not yet confirmed a link between a high fat diet and breast cancer.

• Most studies show no connection between dietary fat and breast cancer. But, most of the studies so far have looked at postmenopausal women. In 2003 the Nurses' Health Study found that among younger, premeno­pausal women, a high intake of animal fat in the forms of red meat and high-fat dairy products was connected with a higher risk of breast cancer. Fat from vegetable sources did not increase risk.

• Several European studies suggest that monounsaturated fats reduce the risk for breast cancer, as well as colon and prostate cancers. Even so, the findings are preliminary, and more research is needed to tell for certain whether the type or amount of fat you consume has any effect on breast cancer risk.

Folic acid. A diet rich in folic acid might reduce the risk of breast cancer.

• Some research has shown that women who take 600 mcg (micrograms) or more of folic acid a day and who also drink more than one alcoholic beverage a day do not have a higher risk of breast cancer than women who drink less.

• You can decrease your risk of breast cancer by limiting your alcoholic intake to one drink a day or less and taking 600 mcg of folic acid a day.

• You can get folic acid from a multivitamin, as well as from foods such as fortified bread and breakfast cereals, liver, and lentils and other legumes. Many cold cereals are fortified with 100 mcg of folic acid per serving, and most multivitamins provide 400 mcg.

Fruits and vegetables. Once again, evidence is far from conclusive.

• In the Nurses' Health Study, women who ate five or more servings a day of fruits and vegetables had a modestly lower risk of breast cancer than did women who ate just two servings. The relationship was strongest among premenopausal women, especially those with a family history of breast cancer.

• The Harvard researchers who conducted the study recommend dark leafy green vegetables and orange-red fruits and vegetables. These foods are high in vitamin A, and preliminary research suggests that getting too little vitamin A may modestly raise the risk of breast cancer. The recommended daily intake is 4,000 international units (IU).

Soy. Isoflavonoids are specific types of plant estrogen that are abundant in soy products like soybeans, tofu, and soymilk.

In laboratory studies, isoflavonoids seem to block the cancer-initiating action of other estrogens. Some studies, however, have found that women who took soy supplements had increased growth of breast cells, which might increase the potential for breast cancer development. Even in studies on mice, transplanted human breast cancer cells multiplied when the mice were fed doses of soy.

More human studies are needed. Meanwhile, a sensible approach is to enjoy soy as part of a healthy diet. Avoid unusually large amounts of soy and don't take soy supplements.

Last updated:	April 23, 2007