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Soy and Breast Cancer: The Facts

Banu Arun, M.D., from the department of breast medical oncology at the University of Texas M.D. Anderson Cancer Center, helps us sort fact from fiction:

Q What's the deal with soy and hormones?

A Whole soybeans have a balance of plant estrogens, as do other foods, like lentils and berries. However, when certain components are isolated out, such as isoflavones, the hormonal balance is thrown off, which is when we caution certain groups of women.

Q Which women?

A We advise women who've had hormone-positive breast cancer and those who are at high risk for developing the disease to be careful about intake because studies on the effects of soy have been inconclusive; one reports a breast health benefit, while another warns that soy's potential estrogen-like effects could be harmful. So until there are conclusive answers, cautioning these women makes sense. In healthy women, on the other hand, research has yet to indicate a harmful impact on breast cancer risk, meaning that soy can be safely consumed in moderation through whole soy products like tofu and edamame.

Q So for those without a history of breast cancer, how much soy is a good idea?

A An actual amount is hard to measure because, again, research differs, so the advice is the same given for most other foods: Consume it moderately through natural sources, but avoid soy supplements. Plus, because whole soy is a complete protein containing all nine essential amino acids, it's a great alternative to meat, which means there's no reason for most women to avoid it.