Daily Soy Supplement May Reduce Whole Body Bone Loss in Healthy Postmenopausal Women
By Laurie Barclay, MD
Medscape Medical News
October 9, 2009 — A daily soy supplement may reduce whole body bone loss in healthy postmenopausal women without slowing bone loss at common fracture sites, according to the results of a 2-year, multicenter, randomized, double-blind, placebo-controlled, clinical trial reported online in the September 16 issue of the American Journal of Clinical Nutrition.
"Isoflavones are naturally occurring plant estrogens that are abundant in soy," write William W. Wong, PhD, from Baylor College of Medicine in Houston, Texas, and colleagues. "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."
In this study, 403 postmenopausal women were randomly assigned to receive daily supplementation with 80 or 120 mg of soy hypocotyl aglycone isoflavones or placebo plus calcium and vitamin D. Annual evaluations allowed determination of changes in whole body and regional bone mineral density (BMD), bone mineral content (BMC), T scores, and changes in serum biochemical markers of bone metabolism.
Compared with the placebo group, the 120-mg soy isoflavones group had a significantly smaller reduction in whole body BMD both at 1 year (P < .03) and at 2 years (P < .05) of treatment, after controlling for study site, soy intake, and pretreatment values. The 120-mg soy isoflavones group also had smaller decreases in whole body BMD T score at 1 year (P < .03) but not at 2 years of treatment. Soy isoflavone supplementation at either dose appeared to have no effect vs placebo 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," the study authors write. "The attenuated WB [whole body] BMD in healthy postmenopausal women for 2 years probably translates to minimal clinical benefits; yet the long-term significance, particularly with regard to fracture prevention, remains to be determined."
The US Department of Agriculture/Cooperative State Research, Education, and the Extension Service/Initiatives for Future Agriculture and Food Systems, and the National Institutes of Health (NIH) General Clinical Research Center supported this study. The study authors have disclosed no relevant financial relationships.
The soy isoflavone material was provided by Frutarum Netherlands BV (Veenendaal, the Netherlands). The placebo and isoflavone tablets were made and packaged by Pharma Consulting Industries BV (Eede, the Netherlands). The one-a-day multivitamin supplement was provided by Swanson Health Products, Fargo, North Dakota. The calcium carbonate supplement was provided by Source Naturals, Scotts Valley, California.
The contents of this journal article do not necessarily reflect the views or policies of the US Department of Agriculture or the NIH, nor does the mention of trade names, commercial products, or organizations imply endorsement.
Am J Clin Nutr. Published online September 16, 2009.
