Soy Ingredient Prevents Osteoporosis
August 2, 2007—Good news for women looking for ways to keep their bones strong: an ingredient in soy may improve bone mineral density. A new study published in the Annals of Internal Medicine found that 54 mg per day of genistein, a type of isoflavone, had positive effects on bone mineral density in postmenopausal women with mild loss of bone density (osteopenia).
Women in certain parts of the world who eat high amounts of plant-derived estrogen-like compounds (phytoestrogens), particularly isoflavones such as genistein found in soy products, have less risk for osteoporosis than those who eat a Western diet. To evaluate genistein’s effects on bone density, researchers enrolled 389 postmenopausal women between ages 49 and 67 with osteopenia and randomly assigned them to take either 54 mg of genistein or a placebo daily for 24 months. Both the genistein and placebo tablets also contained vitamin D and calcium. Women who took genistein for two years had improved bone mineral density while the women who took only the vitamin D and calcium experienced decreased bone mineral density.
“The data from this two-year study suggest that purified genistein may be a useful therapy for postmenopausal women with osteopenia,” said Francesco Squadrito, MD, an author of the study and professor of Pharmacology in the Department of Clinical and Experimental Medicine and Pharmacology at the University of Messina, Messina, Italy. “The gains in bone mass observed in the women taking genistein were comparable to what is observed clinically with traditional drug treatments for bone loss.”
Because of the apparent bone-preserving effect of phytoestrogens, some women in Western cultures use phytoestrogen supplements or eat soy food products with the hopes of maintaining bone density. But Dr. Squadrito warns that not all phytoestrogen products have proven to be helpful for bone density. “Given the highly purified genistein extract used in this study, it is unlikely that [taking] mixed phytoestrogen supplements or consuming soy foods would produce similar effects on bone density,” said Squadrito. “Most phytoestrogen preparations contain around 1% or less of genistein.”
The study’s authors recommend further research to evaluate the effects of phytoestrogens on bone density, and there are some concerns about safety. “The data from our two-year clinical trial and historical long-term consumption of soy products by Asians suggest that genistein is safe for breast and endometrial tissue, as well as the cardiovascular system,” said Squadrito.
However, one recent study found that about 1 in 25 women developed precancerous changes in the uterus after taking soy isoflavones for five years, whereas no such changes were seen after 2 1/2 years of taking the supplement. The cause of these changes is unclear, and further research is needed to evaluate the effects of genistein on uterine and breast tissue.
Women contemplating taking dietary supplements for bone health should talk with a doctor who can recommend the appropriate supplements and discuss the risks and benefits of such products.
(Ann Intern Med 2007;146:839–47)
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Jane Hart, MD, board-certified in internal medicine, serves in a variety of professional roles including consultant, journalist, and educator. Dr. Hart, a Clinical Instructor at Case Medical School in Cleveland, Ohio, writes extensively about health and wellness and a variety of other topics for nationally recognized organizations, Web sites, and print publications. Sought out for her expertise in the areas of integrative and preventive medicine, she is frequently quoted by national and local media. Dr. Hart is a professional lecturer for healthcare professionals, consumers, and youth and is a regular corporate speaker.
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