Soy Supplements and Bone Health

About 20 million American women have osteoporosis, a thinning of the bones that increases risk of bone fracture. Postmenopausal women are particularly susceptible, because their estrogen production has stopped. Estrogen plays an important role in slowing bone loss. So after menopause, bone loss can increase dramatically, and some women and their doctors may consider estrogen replacement therapy. Estrogen replacement therapy has been shown to reduce bone loss and fractures, but it carries some health risks.

As an alternative, taking over-the-counter soy isoflavone supplements is becoming common among postmenopausal women. But there is no documented scientific evidence of either their long-term safety or efficacy in preventing osteoporosis.

William Wong, a nutritionist with the Children's Nutrition Research Center (CNRC) at Baylor College of Medicine in Houston, Texas, aims to get some answers to those two important questions. He is leading a $4.5 million national study called OPUS (Osteoporosis Prevention Using Soy) that will determine the benefits, safety, and correct dosages of soy isoflavone supplements to prevent osteoporosis in postmenopausal women.

Begun in the spring of 2003, the project will enroll 400 women divided among CNRC, the University of Georgia in Athens, the University of California at Davis, and the Kaiser Foundation Research Institute in Oakland, California, and will follow them for 2 years. CNRC is the coordination center, and Wong is the project director.

Though earlier studies have indicated that soy isoflavones may help prevent osteoporosis and reduce symptoms of menopause, these studies were usually short term and involved only a small number of volunteers. OPUS is a long-term study of whether natural soy isoflavones really are beneficial and safe. A third of the women will receive isoflavone supplementation at 80 milligrams per day, a third will receive 120 milligrams per day, and the remaining third will receive a placebo.

Confirming skeletal benefits from soy isoflavone consumption could translate into reduced health care costs for treating osteoporosis and increased production, sales, and consumption of an important U.S. agricultural product. As a part of this study, funded by the U.S. Department of Agriculture, findings will be disseminated to researchers, educators, health care professionals, and consumers through Texas A&M University and the Cooperative Extension System.

CNRC is operated by Baylor College of Medicine in cooperation with Texas Children's Hospital and the Agricultural Research Service.—By Alfredo Flores, Agricultural Research Service Information Staff.

William W. Wong is at the USDA-ARS Children's Nutrition Research Center at the Baylor College of Medicine, 1100 Bates St., Houston, TX 77030; phone (713) 798-7168.

"Soy Supplements and Bone Health" was published in the April 2004 issue of Agricultural Research magazine.