Nutrition researchers at the University of California, Davis, and Kaiser Permanente in Sacramento are seeking women between the ages of 40 and 60 to take part in a national study to see if a soybean supplement can prevent brittle bones, a condition known as osteoporosis.

Osteoporosis affects about 20 million women in the United States, causing bone loss and an increased risk of broken bones. Postmenopausal women are most likely to be affected. Hormone replacement therapy (HRT) with estrogen has been shown to reduce bone loss and fractures, but may be associated with increased risks of breast cancer and heart disease.

Those concerns have increased recently after a large clinical trial of HRT, undertaken as part of the Women's Health Initiative (WHI), was stopped three years early due to an apparent increase in heart disease and breast cancer.

Soybeans contain natural plant estrogens, called isoflavones. Short-term studies have shown that isoflavone supplements can prevent bone loss in women at or after menopause.

The OPUS (Osteoporosis Prevention Using Soy) study will test whether isoflavone supplements prevent bone loss and changes in bone metabolism over a two-year period.

"We have good preliminary data that the natural isoflavones extracted from soybeans may be as effective as traditional hormone replacement therapy in preventing osteoporosis in menopausal women with little or no side effects," says Dr. Michael Murray, a lead investigator for this study. "However before physicians can embrace this natural alternative and recommend it for their patients, we need stronger evidence that it is really going to work."

Potential participants must be healthy women ages 40 to 60 who are at least one year past menopause and willing to stop taking HRT for up to 2 1/2 years. Volunteers will be randomly assigned to take two different doses of isoflavone supplement or a placebo (sugar pill). Neither the investigators nor the participants will know which dose they are taking. All volunteers will get a daily multivitamin and calcium supplement.

Potential participants will undergo a screening interview by telephone, a physical exam, bone mineral density scan and blood analysis before being assigned to study groups. Participants will have to return to the clinic every six months to pick up new supplements and each year for two years for blood tests, bone density scans and a physical examination including a mammogram and pap smear. Participants will be reimbursed.

The collaborators in the study are Baylor College of Medicine, the University of Georgia, UC Davis and Kaiser Permanente. The California study site will be led by Francene Steinberg, assistant professor in nutrition at UC Davis, and Michael Murray, director of endocrinology, Kaiser Permanente, and clinical assistant professor of obstetrics and gynecology at UC Davis. The study is funded by a grant from the U.S. Department of Agriculture.

For information about joining the study, call (530) 752-5510 or (916) 614-4646.