Soy & Breast Cancer

soy - Cook for Your Life

Is it safe for me to eat soy? I am a breast cancer survivor and it seems like the information is so conflicting. 

The controversy over soy and breast cancer has been ongoing for some years. But recently published studies hopefully have resolved this issue.

Early investigations targeted soy as a possible risk factor because it contains a group of proteins, called isoflavones, that mimic estrogen. Higher levels of estrogen are associated with an increased risk of breast cancer. Animal studies showed that mice fed isoflavones in fact, did have an increased risk of breast cancer. Even though mice metabolize isoflavones differently than humans, healthcare providers erred on the side of caution and advised breast cancer patients against any consumption of soy.

In the past few years, results of human studies have finally been published. They looked at women in the United States as well as Asia, where soy is consumed more regularly. These large population studies show that soy products may even be protective in certain circumstances and at the very least they are not harmful. These results are true even for women taking tamoxifen or aromatase inhibitors, two medications for estrogen receptor + breast cancer.

Soy products consumed in the early years of puberty may be the most protective. Consuming soy later in life appears neutral.  However, there is some evidence that soy, aside from its isoflavone content, may have anti-cancer properties.  It may protect cells from damage (anti-oxidants), reduce inflammation, discourage tumor cell proliferation, and increase the destruction of tumor cells.

Bottom line:  These recent studies should put to rest the controversy over soy and breast cancer risk.  Women with breast cancer, even if estrogen-receptor-positive, or women at risk for breast cancer can enjoy soy foods as a part of a balanced diet.

Whole food forms of soy are tofu, tempeh, soymilk, edamame, soy nuts, and miso. Find some great tofu and tempeh recipes here >>

Kate Ueland, MS, RD, specializes in oncology nutrition, primarily working with breast, ovarian, renal, and melanoma cancer patients throughout all stages of the cancer journey at Seattle Cancer Care Alliance (SCCA) in Seattle, WA. As Cook for Your Life’s nutrition advisor and editor, Kate ensures all culinary content adheres to the Academy of Nutrition and Dietetics and follows science-based guidelines.

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