PHILADELPHIA, Oct 19, 2004 (United Press International via COMTEX) -- A U.S. study released Tuesday has negated theories estrogens in soy foods that protect against breast cancer also impair fertility.

"Our results suggest that a high-soy diet probably won't compromise fertility in women," said Dr. Jay Kaplan, lead researcher from Wake Forest Baptist Medical Center. Along with researchers at the Emory University School of Medicine, the study addressed how women in Asian countries where a lot of soy is consumed have dramatically lower rates of breast cancer than women in the United States.

One explanation has been plant estrogens, called isoflavones, increase menstrual cycle length or reduce ovarian hormones, which would impair fertility.

In a year-long study using monkeys and controlled diets using soy for one group, but not the other, no correlation between menstruation and breast cancer was found.

"Soy treatment did not change any characteristics of the menstrual cycle, including length, amount of bleeding or hormone levels," said Kaplan. "This suggests that any protection that soy may provide against breast cancer does not come from changes in the menstrual cycle."

The research was presented Tuesday at the annual meeting of the American Society for Reproductive Medicine in Philadelphia.

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