Soy foods are rich in isoflavones, a group of phytoestrogens that have been hypothesized to lower the risk of breast cancer. According to a new study published in the December 9, 2009 issue of the Journal of the American Medical Association, eating soy foods may reduce the risk of death and cancer recurrence among women with breast cancer.

These results come from the Shanghai Breast Cancer Survival Study, which included 5042 women who had survived breast cancer. During an average follow-up period of 3.9 years, 444 deaths and 534 recurrences or breast cancer-related deaths were documented in 5033 surgically-treated breast cancer patients. Consumption of soy food was associated with lower rates of death and cancer recurrence. Interestingly, this inverse association with soy intake was found among women with both estrogen receptor-positive and estrogen receptor-negative breast cancer.

The estrogen-like effect of isoflavones and the potential interaction between isoflavones and the breast cancer treatment tamoxifen have raised concerns about soy consumption in breast cancer. However, this study demonstrates that, among Chinese women with breast cancer, eating soy was significantly associated with a decreased risk of breast cancer death and recurrence, whether the women were taking tamoxifen or not. So, it seems that soy is safe, and may even be beneficial, for breast cancer patients.
 

Source:

JAMA. 2009;302:2437-2443.