Results of a new study suggest that concerns about a possible link between soy consumption and increased breast cancer risk may be unfounded.
Some doctors and scientists have previously expressed concerns that the isoflavones found in soybeans and soy-based products could increase a woman’s risk of breast cancer, or increase the likelihood of the cancer returning.
Isoflavones are natural compounds that act like weak forms of the female hormone estrogen. Isoflavones are thought to bind to estrogen receptors in the same way as estrogen, which could potentially stimulate the growth of breast cancer cells and even lessen the effectiveness of a drug commonly used to prevent cancer reoccurrence in women with estrogen-sensitive breast cancer. Thus, some doctors advise breast cancer patients to avoid or limit their consumption of soy products.
But that may be changing.
The new study included an analysis of 9,514 breast cancer survivors in the U.S. and China. Daily soy isoflavone intake was measured using food frequency questionnaires, then correlated with total deaths and breast cancer reoccurrence.
Despite large differences in soy consumption by country, soy consumption was negatively associated with cancer reoccurrence in both American and Chinese women. In fact, women who consumed 10 milligrams or more of soy isoflavones had a 25 percent lower risk of breast cancer recurrence than those who consumed less than four milligrams daily.
Further, consumption of more than 10 mg of soy isoflavones per day was also associated with reduced overall and breast cancer-specific mortality.
It’s pretty easy to achieve this protective effect through diet alone (and researchers are still wary of soy isoflavone supplements anyway). The dietary equivalent of 10 mg of soy isoflavones is about 1/2 cup of soymilk or 1/4 cup of tofu.
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