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Soy and Breast Cancer: What's the Link?

What experts say about whether soy is helpful, harmful, or neutral when it comes to breast cancer.

Soy's Form May Matter

Bill Helfreich, PhD, a nutrition professor at the University of Illinois, has been studying soy for more than a decade. His studies in mice were among the first to show that soy isolates stimulate breast cancer cell growth. He bristles at the suggestion that the new positive research on soy invalidates his own earlier work.

“The science is clear," Helfreich tells WebMD. “Isoflavone supplements are estrogenic. They do almost everything estrogens do, including stimulating estrogen-responsive tumors.”

Helfreich's studies didn't show that whole soy promoted tumor cell growth. He agrees that eating minimally processed soy may be good for everyone, including breast cancer survivors.

“I’ve been called anti-soy, but that’s not right,” he says. “Soy is a fine legume, but there is nothing magical about it and it should not be promoted as medicine.”

Helfreich says Westerners who eat minimally processed soy foods, as Asians tend to do, will probably derive similar health benefits. “But you can’t take a soy supplement and eat biscuits and gravy and call it an Asian diet,” he says.

Helferich says breast cancer survivors can safely eat soy foods in moderation.

Despite the new research, Jennifer Mukai says she won’t be adding much more soy to her diet in the near future.

Mukai is taking aromatase inhibitors, prescription drugs that help lower the amount of estrogen in the body.

Because the whole point of the treatment is to eliminate estrogen from her body, Mukai says it doesn’t make sense to eat foods that contain estrogen, even in very small amounts.

Reviewed on September 27, 2010

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