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By Ryan Perkins

M.D. on 04/04/2017

The Soy - Breast Cancer Connection

For years, the health community has been waging a debate on the connection between soy and cancer. Now a new study published this month in the journal Cancer indicates that soy appears to not only be safe for women with breast cancer –it may even be beneficial. 

Some of the controversy about soy stems from the fact it contains isoflavone, an estrogenic compound, or plant estrogen, that some worry might fuel certain breast cancers or absorb the anti-estrogen drugs prescribed to shrink the tumors. Conversely, others believe the weaker plant-based estrogens might offer protection by binding to breast cells and squeezing out the harmful cancer-causing estrogens. 

Previous studies revealed women in Asian countries who consumed large amounts of soy were less likely to die from breast cancer or experience recurrence than women who ate less soy, further boosting the pro soy debate. 

In an attempt to clear the confusion about soy and breast cancer, Dr. Fang Fang Zhang, an assistant professor at Tuft University’s Friedman School of Nutrition Science and Policy, studied women in the United States and Canada diagnosed with the disease and found that over a 9-year period, those who consumed more soy did not have a higher risk of dying from breast cancer than women who consumed less. In fact, the study found women who ate even one-half to one serving of soy a week were 20 percent less likely to die of any cause than those who consumed less. 

Study participants with estrogen- and progesterone-negative breast cancers saw the largest drop in mortality, while death rates in women with hormone-driven breast cancers neither increased nor decreased. Mortality rates for those with breast cancer being treated with anti-estrogen drugs also did not appear to be affected by soy consumption.  

While the results of this single study are not enough to suggest women with breast cancer should increase soy intake, it provided no indication that soy is harmful. I anticipate future studies will provide even more clarity on the effects of soy on breast cancer. Meanwhile, my recommendation is that women with breast cancer continue to eat healthfully and enjoy a variety of foods, including soy products. 

For questions about soy consumption and breast cancer or for more information on the connection between diet and cancer, contact Ackerman Cancer Center through our confidential online form.

All my best,

Ryan Perkins, M.D. 

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