Many women take estrogen to help ease symptoms of menopause. But estrogen is also thought to be a factor in breast cancer, so many women don't want to take it. Phytoestrogens from plants are an alternative thought to protect against some estrogen-caused cancers. Italian researchers looked at women taking soy-derived phytoestrogens to find out what effects they had on a different part of the body—the endometrium, or lining of the uterus.

What the researchers wanted to know: How does taking soy phytoestrogens affect the endometrium?

What they did: Starting in 1996, 376 healthy women who had stopped menstruating took either soy isoflavones or a placebo for five years. The women were randomly assigned to one of the pills, and neither they nor their doctors knew which they were taking. At the beginning, middle, and end of the study, researchers took a biopsy of endometrium from each woman.

What they found: Women who took soy were more likely to have abnormal growth of their endometrium after five years than women who took a placebo; six women taking soy had the growth, while none on the placebo did.

What the study means to you: Taking phytoestrogens may have risks, especially for women at risk of endometrial cancer.

Caveats: The women were on a relatively high dose of soy isoflavones—150 mg a day.

Find out more: Those five women had endometrial hyperplasia, described in this article: www.medem.com

Read the article: Unfer, V. et al. "Endometrial Effects of Long-Term Treatment With Phytoestrogens: A Randomized, Double-Blind, Placebo-Controlled Study." Fertility and Sterility. July 2004, Vol. 82, No. 1, pp. 145–148.

Abstract online: www.fertstert.org