ARS | Publication request: Soy isoflavone supplementation and bone mineral density in menopausal women: a 2-y multicenter clinical trial

Submitted to: American Journal of Clinical Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 17, 2009
Publication Date: November 13, 2009
Citation: Wong, W.W., Lewis, R.D., Steinberg, F.M., Murray, M.J., Cramer, M.A., Amato, P., Young, R.L., Barnes, S., Ellis, K.J., Shypailo, R.J., Fraley, J.K., Konzelmann, K.L., Fischer, J.G., Smith, E.O. 2009. Soy isoflavone supplementation and bone mineral density in menopausal women: A 2-y multicenter clinical trial. American Journal of Clinical Nutrition. 90(5):1433-1439.

Interpretive Summary: Osteoporosis is a major health concern among menopausal women. Hormone replacement therapy can prevent bone loss but comes with increased cancer risks. Plant hormones or phytoestrogens such as soy isoflavones are believed to have benefit against bone loss without the increased cancer risks. To find out if soy isoflavones can reduce bone loss, 403 menopausal women were enrolled in a two-year study where a third of the women took 3 pills per day that provided 120 mg of soy isoflavones, a third took 3 pills per day that provided 80 mg of soy isoflavones and the remaining third took 3 pills per day that contained no soy isoflavones. Bone density of all the women was measured before the women began taking any pills and after 1 year and 2 years of treatment. The results showed that women who were taking 120 mg of soy isoflavones per day had the least whole-body bone density loss after 1 year and 2 years of treatment.

Technical Abstract: Isoflavones are naturally occurring plant estrogens that are abundant in soy. Although purported to protect against bone loss, the efficacy of soy isoflavone supplementation in the prevention of osteoporosis in postmenopausal women remains controversial. Our aim was to test the effect of soy isoflavone supplementation on bone health. A multicenter, randomized, double-blind, placebo-controlled 24-mo trial was conducted to assess the effects of daily supplementation with 80 or 120 mg of soy hypocotyl aglycone isoflavones plus calcium and vitamin D on bone changes in 403 tmenopausal women. Study subjects were tested annually, and changes in whole-body and regional bone mineral density (BMD), bone mineral content (BMC), and T scores were assessed. Changes in serum biochemical markers of bone metabolism were also assessed. After study site, soy intake and pretreatment values were controlled. Subjects receiving a daily supplement with 120 mg soy isoflavones had a statistically significant smaller reduction in whole-body BMD than did the placebo group both at 1 y (P < 0.03) and at 2 y (P < 0.05) of treatment. Smaller decreases in whole-body BMD T score were observed among this group of women at 1 y (P < 0.03) but not at 2 y of treatment. When compared with the placebo, soy isoflavone supplementation had no effect on changes in regional BMD, BMC, T scores, or biochemical markers of bone metabolism. Daily supplementation with 120 mg soy hypocotyl isoflavones reduces whole-body bone loss, but does not slow bone loss at common fracture sites in healthy postmenopausal women.