Eating soy-based foods may have beneficial effects for women who have had surgery.
THE QUESTION Soy-based foods contain isoflavones, which act in a manner similar to estrogen, a natural hormone that is thought to play a role in the growth of cancer cells. Should women with breast cancer, then, avoid foods containing soy?
THIS STUDY analyzed data on 5,033 women who had surgery for breast cancer. In the next four years, 534 of them either had a cancer recurrence or died of the disease. Women who consumed, on average, the most soy (more than 15 grams of soy protein a day) were 32 percent less likely to have had their cancer return and 29 percent less likely to have died of breast cancer than were women who took in the least soy (less than five grams a day). The benefits were the same whether the women had breast cancer that was estrogen-receptor-positive or -negative. There was also no difference noted between women being treated with tamoxifen and those not being treated with the drug.
WHO MAY BE AFFECTED? Women with breast cancer. The disease strikes about one in eight women in the United States, although U.S. breast cancer rates have declined slightly each year for the past decade.
CAVEATS The findings do not apply to soy supplements. Dietary data were based on the women's responses on periodic questionnaires. All women lived in China, where average soy consumption is higher than in the United States. Women with the most soy in their diets also ate more vegetables and fish and exercised more, which may have affected the results.
FIND THIS STUDY Dec. 9 issue of the Journal of the American Medical Association.
-- Linda Searing
The research described in Quick Study comes from credible, peer-reviewed journals. Nonetheless, conclusive evidence about a treatment's effectiveness is rarely found in a single study. Anyone considering changing or beginning treatment of any kind should consult with a physician.