Soy and Breast Cancer: Questions Remain

Monday, February 17, 2003

ROCHESTER, Minn. — Does soy help prevent or promote breast cancer? Right now, it's impossible to say, according to the February issue of Mayo Clinic Women's HealthSource.

Experts have had good reason to suspect that a diet high in soy may help protect against breast cancer. Studies show that the risk of breast cancer is six times higher for American women than for women who live in Asian countries where soy foods are commonly eaten.

Soy foods — soy milk, tofu and soy nuts — contain isoflavones, a weak form of estrogen that mimics naturally occurring estrogen. Genistein, a specific isoflavone, had been thought to reduce the risk of breast cancer.

Isoflavones have become so popular that they are now available as diet supplements. But research on the effectiveness and safety of isoflavone supplements is contradictory. Some studies suggest that taking isoflavones may help prevent breast cancer. Other studies suggest that consuming genistein may carry some risk of actually promoting breast cancer.

Soy foods have been eaten safely for centuries and can help improve cholesterol levels and promote heart health. But for now, no one knows how beneficial or safe it is to use isoflavones as a diet supplement.

Carol Lammers
507-284-5037 (days)
507-284-2511(evenings)
email: newsbureau@mayo.edu

Mayo Clinic Women's HealthSource is published monthly to help women enjoy healthier, more productive lives. Revenue from subscriptions is used to support medical research at Mayo Clinic. To subscribe, please call 800-876-8633, extension 9PK1.

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