Isoflavones, a naturally occurring compound found in soybeans, were once thought to provide an alternative to estrogen therapy as a way to protect postmenopausal women from osteoporosis. However, research provided by the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) recently found evidence that soy isoflavone tablets may not help preserve bone density as originally thought.
The NIAMS study builds on a three-year study conducted by Lee Alekel, Ph.D of Iowa State University and colleagues at the USDA Agricultural Research Service's Western Human Nutrition Research Center, which provided evidence that refuted the idea that soy isoflavone tablets helped prevent bone loss in women. Researchers concluded that women taking soy isoflavone tablets did not experience any negative effects. However, the widely-held belief that they helped maintain bone strength was questionable.
According to NIAMS, 250 healthy, postmenopausal women participated in the study. The subjects were randomly selected to receive one of two daily doses of isoflavones: 80 or 120 mg. The other randomly selected group received a placebo. All of the participants received 500 mg of calcium and 600 IU of vitamin D daily.
At the end of the three-year study, the women in both groups experienced similar losses of bone density in their spine, hip, and total body. The women in the group taking 120 mg of soy isoflavone experienced slightly less bone loss, but the effect was minimal.
