Ask a naturopathic doctor:
Question: Dr. Erdman, I’m a breast cancer survivor – can I can safely include soy in my diet? How will it affect my risk of recurrence?
For breast cancer survivors, the current consensus is that moderate consumption of soy (up to 10g per day of tofu, soy milk, whole soybeans/edamame) is not harmful, and even suggests an association with a reduced risk of recurrence and improved survival.
This is based on 3 large-scale studies that included over 9500 breast cancer survivors (only women were included). The protective effect was seen regardless of whether the cancer was hormone sensitive (Estrogen/Progesterone Receptor Positive), and whether the woman was taking drugs like Tamoxifen and Anastrazole, which are commonly taken to prevent recurrence after completing surgery, radiation or chemotherapy in hormone sensitive disease.
Take note that the benefit seen with soy in breast cancer survivors may not be due to soy itself. Rather, soy may be an indicator of a diet that includes more plant-based foods, including fruits, veggies and plant protein like whole soy foods, which has been shown to reduce overall cancer risk.
Until we know this – If you’re not a regular consumer of soy foods, the research is not strong enough to suggest that they should be used as standard therapy to reduce recurrence risk. But, if you are someone who includes whole soy foods as a healthy source of plant-based protein in your diet, you can take heart that moderate amounts are safe.
Source: Kaczor T. The Effects of Soy Consumption on Breast Cancer Prognosis. Natural Medicine Journal Nov 2012;4(11)