Diet may play a role in treatment of breast cancer, but a new study has found that, at the levels commonly consumed by African-American, Latina, and White women living in the United States, phytoestrogens have little effect on lowering breast cancer risk.
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September 28, 2001
By Alice Chang, M.D.
Harvard Medical School
How does this article relate to you?
Phytoestrogens are the active ingredients in many herbal or alternative therapies treating menopausal symptoms or high cholesterol. Examples of common dietary sources include soy, soy milk and tofu, but many of the compounds sold without a prescription to treat menopause, premenstrual syndrome or to lower cholesterol include phytoestrogens. An important question has been whether the "natural" phytoestrogens increase a woman's breast-cancer risk since they have estrogenlike effects. This study adds supportive evidence that, so far, phytoestrogens have not been associated with an increased risk of breast cancer.
In addition, it does not support the use of phytoestrogens specifically to reduce breast-cancer risk. Some people have wondered if lower rates of breast cancer in Asia were related to higher levels of phytoestrogen in the Asian diet.
One major issue prevents us from being able to say that phytoestrogen alternative therapies are safe: The phytoestrogen levels in the diets of women in this study appear to be very low. The amount was equal to roughly one serving of tofu per week — much less than what we recommend for treatment of any of the above conditions. The researchers did not study the diets of Asian women who are more likely to have higher levels of phytoestrogens in their diet. In addition, if you are using a product sold over the counter, remember that these products are not regulated by the U.S. Food and Drug Administration. There is no way to know for sure the exact amount of phytoestrogens in the product. Don't necessarily believe the labels.
What changes do you need to make?
Although this information is reassuring, it still would not change my general practice of warning people that there is no definite information about the risk of breast cancer when using phytoestrogens. Women who do not have other risks for breast cancer are probably at lower risk for breast cancer using phytoestrogens than standard hormonal therapy, but we do not know for sure. I also advise woman with a strong family history of breast cancer against using alternative therapies with estrogenlike effects. I do not think we have enough information about the plant estrogens to expose women with a strong family history of breast cancer to additional potential risks. Nor is there convincing proof that women can lower their risk by adding phytoestrogens to their diet.
What can you expect in the future?
The jury is still out on the final answer to this question. Studies will need to follow women who are including higher levels of phytoestrogens in their diet before we are reassured that there is no significant breast-cancer risk. The Women's Health study currently is investigating this and other important questions, but we have many years to wait before we can have good answers.
Related links:
Complementary and Alternative Medicine: Menopause
