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By Amy Norton
NEW YORK, Mar 20 (Reuters Health) - An over-the-counter supplement marketed as a natural way to prevent bone thinning appears ineffective, according to results of a 3-year study in Denmark. In fact, researchers found, some women who took the supplement experienced a drop in their white blood cell counts, a condition that can impair the immune system.
The supplement, called ipriflavone, is a synthetic version of one of the isoflavones, which are plant-based compounds with estrogen-like effects. Soy protein is rich in isoflavones, and some research suggests that a diet heavy in soy products, such as tofu, helps prevent osteoporosis. While ipriflavone is sold in health-food stores in the US, it is used as a prescribed osteoporosis treatment in Europe and Japan.
But the supplement may not live up to its claims, researchers report in the March 21st issue of The Journal of the American Medical Association. In a study of 474 postmenopausal women with low bone mineral density, investigators found that 3 years of ipriflavone treatment not only failed to slow bone loss, but it also triggered a drop in white blood cells in some women.
Dr. Peter Alexandersen of the Center for Clinical and Basic Research in Ballerup, Denmark, led the study. He and his colleagues had half of the study participants take 200 milligrams of ipriflavone three times per day, while the other half took placebo, or inactive, pills.
All of the women took calcium supplements. By the end of the study, there was no difference in bone density between the two groups. And about 13% of women on the supplement developed lymphocytopenia, a drop in white blood cells that, in most of these cases, resolved after the women stopped taking ipriflavone.
Although earlier studies have suggested ipriflavone does fight bone thinning, Alexandersen's team notes, these findings suggest that compared with other osteoporosis treatments, ipriflavone offers little benefit.
"Ipriflavone bought at a health-food store is not a substitute for recommended osteoporosis treatments," Dr. Lawrence G. Raisz, of the University of Connecticut Health Center in Farmington, said in an interview with Reuters Health. Current recommendations for preventing and managing osteoporosis include getting enough calcium and vitamin D, exercising regularly and using treatments that slow bone loss such as hormone replacement therapy.
However, Raisz said, this study does not suggest that isoflavones and soy-based diets are ineffective against bone thinning. Ipriflavone, he noted, is an isoflavone derivative, and not the real thing found in soy.
"This doesn't rule out the possibility that some combination of isoflavones in soy protein might work," said Raisz, who also heads the scientific advisory board for the National Osteoporosis Foundation.
What is needed, he said, are controlled trials of the role of soy in preventing and treating bone loss.
SOURCE: The Journal of the American Medical Association 2001;285:1482-1488.
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