Soy and Breast Cancer Risk: The Straight Story

Patient Expert

Credit: Thinkstock

Editors’ note: This is a “Second Opinion” sharepost, where patient experts share their take on research, news, and trends in health and medicine. Their views do not necessarily reflect the opinions or views of

A study released March 6, 2017 in Cancer, the peer-reviewed online journal of the American Cancer Society, has been picked up and broadcast by mainstream media. The message: Consuming soy products may help prevent breast cancer recurrence.

Does this mean breast cancer survivors wanting to improve their survival chances should increase their intake of tofu and edamame, and swap soy milk for skim milk in their latte grande?

Not necessarily. This new study is another example of the importance of understanding the entire message, not just listening to media sound bites.

Stretching back at least 20 years, research has gone back and forth about the effects of soy consumption, either positive or negative, for breast cancer survivors.

Isoflavones in soy have been shown to reduce breast cancer tumor growth in lab studies. But those same compounds, due to their estrogen-mimicking qualities, have been shown in some studies to potentially increase risk of recurrence for women with hormone-receptive breast cancer.

The current study indicates that for women with hormone-negative breast cancer—chiefly, triple-negative breast cancer (TNBC), a subset of about 20 percent of all breast cancer cases—soy may lower the risk of dying by about 21 percent. The effect is also seen in women not treated with hormone therapy (e.g., tamoxifen or an aromatase inhibitor).

This same benefit isn’t enjoyed by the approximately 80 percent of survivors with hormone-receptive cancer: the new study showed no relationship between consumption of soy and reduced mortality.However, this latest study also didn’t show soy products doing this large group of survivors any harm — a departure from scattered earlier studies.

The takeaway?

Given the current news, if you’re a TNBC survivor, consuming soy products may help you live longer. But if you’re in the large group of survivors whose cancer is hormone-responsive, soy doesn’t reduce your risk of dying from breast cancer.

However, soy also doesn’t appear to increase mortality risk. And given the healthy properties of a plant-based diet, “it doesn’t hurt” should give many of us the green light to keep pouring soy milk over our whole-grain breakfast cereal each morning.

See More Helpful Articles:

Busting Soy Myths So You Can Enjoy Soy

Eat to Live: Breast Cancer and Diet

What Foods Prevent Breast Cancer?

Soy: Latest Study Shows No Increase in Breast Cancer Risk

Breast cancer survivor and award-winning author PJ Hamel, a long-time contributor to the HealthCentral community, counsels women with breast cancer through the volunteer program at her local hospital. She founded and manages a large and active online survivor support network.