Q. What's the scoop on these "bioidentical" hormones I keep hearing about?

A: It's a tough time to be a menopausal woman. A few years back, the Women's Health Initiative published research strongly indicating that hormone replacement therapy (HRT) boosts the chances of breast cancer, heart disease, and other problems. About a year after large numbers of women stopped taking HRT (primarily horse-derived Premarin and PremPro) based on those findings, a study showed a dramatic (approximately 7 percent) drop in breast cancer diagnosis in 2003.

Bioidentical, or natural, hormones are the chemical equivalent of what a woman's body produces. In contrast, horse-derived hormones (or conjugated equine estrogens) contain a mixture completely foreign to human biochemistry and more accurately referred to as xenoestrogens. Although bioidentical hormones are often derived from plant sources, they also can be synthetically produced (the term refers to their chemical structure, not their source).

According to one recent data review (Alternative Medicine Review, 2006, vol. 11, no. 3), bioidentical hormones do appear to be effective in treating menopausal symptoms. And research suggests they may have fewer potentially negative side effects than their horse-derived counterparts. Specifically, they may carry less risk for breast cancer and blood clots.

Longer-term human studies are needed to demonstrate that bioidentical hormones won't cause the same kinds of problems as conventional HRT. If you choose to give them a go (with the guidance of a health care practitioner), keep in mind that while they seem to be a better option than HRT, it is simply too soon to tell if they are risk free.

This Q&A was written by Victoria Dolby Toews, MPH, a health journalist based in the Pacific Northwest, where she and her family enjoy hiking and cycling.