Soy Foods and Breast Cancer

For the past several years, the advice given to breast cancer survivors by their oncologists simply didn’t make much sense. I must have heard this from dozens of women: “I was told to avoid soy because it would make the cancer worse.” They’d been told that soy “feeds” cancer, like adding gasoline to a smoldering fire. What an image!

In Asia, where soy intake is many times higher than ours, breast cancer rates are lower. Additionally, and likely due to soy’s estrogen-like effect, women report far fewer menopausal symptoms than in the West.

Even though it’s been demonstrated that soy has anti-cancer properties and can improve both heart and bone health, were oncologists correct in advising their breast cancer patients to stay away from soy and just stick to the breast cancer drug Tamoxifen?

No, they weren’t correct. It was bad advice from the start.

In an analysis of 5042 breast cancer survivors published this week in the Journal of the American Medical Association (JAMA), epidemiologists proved beyond a shadow of a doubt that survival after breast cancer–defined as lower mortality and absence of return of the cancer–was improved by regular intake of soy-based foods.

How soy, an estrogen-like food source, protects is quite interesting. Rather than stimulate the cancer to grow, the “soy-estrogen” molecule blocks the hormone receptor site on the cancer cell from being stimulated by a woman’s own ovary-produced estrogen. Acting as a weaker estrogen, soy actually produces an anti-estrogen effect, much like Tamoxifen. In fact, when researchers compared the outcomes of women who ate a lot of soy foods with the outcomes of women who didn’t eat much soy but took Tamoxifen, the overall survival/recurrence rates were pretty much the same.

Not surprisingly, this particular article didn’t address the question of whether or not a high soy food intake actually could prevent breast cancer in the first place. It didn’t need to. That’s a given.

Now if oncologists would just stop frightening women about vitamins and antioxidants, 2009 might end on a positive note.

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