"Natural hormones are bioidentical," says John Lee, M.D., author of What Your Doctor May Not Tell You About Menopause (Warner Books, 1996), "which means they're absolutely identical to human hormones. Natural hormones are made from plants but must be converted in the lab." In other words, eating soybeans or yams won't provide the body with estrogen or progesterone. However, soy foods have been shown to exert a mild estrogenic effect. "Natural hormones work because the molecule is exactly the same shape as the human molecule," Lee says.

How do you decide if you should supplement with natural hormones? Start by finding a health care provider willing to work with you. "Your physician is someone you need to be able to express yourself with," says Shari Lieberman, Ph.D., a professor at the University of Bridgeport School of Human Nutrition in Connecticut. "They need to be current—if they're still doling out prescriptions for Premarin or some of the other synthetic hormones, they need to know about natural alternatives."

"Although natural hormones are safer," Lieberman says, "I don't believe they should be used indiscriminately." Ideally your health care practitioner should monitor your salivary hormone levels and tailor the dosage of natural hormones to fit your needs. After all, "we share a lot in common as women, but we can't standardize women," says Stephanie DeGraff Bender, M.A., founder of Full Circle Women's Health Inc. in Boulder, Colo. "What's right for one woman might not be right for the next woman."