Harvard Women's Health Watch

Soy may be okay for breast cancer survivors

Prospective studies show no increased risk of recurrence.

At one time, soy seemed to be just the ticket for women: heart-healthy, good for bones, and helpful for hot flashes. And then there was the low rate of breast cancer in soy-consuming countries. But as so often with "miracle foods," closer study has dampened some of the enthusiasm.

Early research indicated that soy protein could lower LDL (bad) cholesterol, but later studies were so unimpressive that the American Heart Association asked that food companies no longer be allowed to label soy products as helpful in preventing heart disease. It's still unclear whether soy does much for bones or hot flashes. And although some studies suggest that it may protect against breast cancer, other research has found that isoflavones (a component of soy that binds to estrogen receptors) can spur the growth of breast cancer cells in test tubes and animals. There's also some concern that soy's estrogenic activity may interfere with tamoxifen, a drug used to prevent recurrence in women with estrogen-sensitive breast cancer. As a result, some clinicians advise patients with breast cancer to limit their consumption of soy or avoid it altogether.

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