Soy isoflavones for osteoporosis: an evidence-based approach.

Effects of soy isoflavones on osteoporosis remain unclear. This review aimed to clarify the effect of soy isoflavones on bone mineral density (BMD) and turnover markers in menopausal women. PubMed and the Cochrane Library were searched in July 2011 for relevant meta-analyses of randomized controlled trials evaluating effects of soy isoflavones on BMD and bone turnover markers. Three meta-analyses evaluated the effects of soy isoflavones on lumbar spine, total hip, femoral neck, and trochanter BMD. Soy isoflavones significantly improved lumbar spine BMD in a moderate manner, but did not affect total hip, femoral neck, and trochanter BMD in menopausal women. Ingestion of soy isoflavones for six months appeared to be enough to exert a beneficial effect on lumbar spine BMD. Two meta-analyses evaluated the effects of soy isoflavones on a bone resorption marker (urine deoxypyridinoline) and two formation markers (serum alkaline phosphatase and osteocalcin). Soy isoflavones significantly decreased urine deoxypyridinoline in a moderate manner, but did not affect serum alkaline phosphatase and osteocalcin in menopausal women. Soy isoflavones may prevent postmenopausal osteoporosis and improve bone strength thus decreasing risk of fracture in menopausal women by increasing lumbar spine BMD and decreasing bone resorption marker urine deoxypyridinoline. Further studies are needed to address factors affecting the magnitude of the beneficial effects of soy isoflavones and to assess the possible interactions between soy isoflavones and anti-osteoporosis drugs, and to verify effects on BMD of other skeletal sites and other bone turnover markers.

Effect of soy isoflavone extract supplements on bone mineral density in menopausal women: meta-analysis of randomized controlled trials.

This study was conducted to clarify the effect of ingesting soy isoflavone extracts (not soy protein or foods containing isoflavones) on bone mineral density (BMD) in menopausal women. PubMed, CENTRAL, ICHUSHI, CNKI, Wanfang Data, CQVIP, and NSTL were searched for randomized controlled trials published in English, Japanese, or Chinese reporting the effects of soy isoflavone extracts on lumbar spine or hip BMD in menopausal women. Trials were identified and reviewed for inclusion and exclusion eligibility. Data on study design, participants, interventions, and outcomes were extracted. Eleven, seven, five, and five trials were finally selected for estimation of the effects on spine, femoral neck, hip total, and trochanter BMD, respectively. Meta-analysis including data from1240 menopausal women revealed that daily ingestion of an average of 82 (47-150) mg soy isoflavones (aglycone equivalent) for 6-12 months significantly increased spine BMD by 22.25 mg/cm2 (95% CI: 7.62, 32.89; p=0.002), or by 2.38% (95% CI: 0.93, 3.83; p=0.001) compared with controls (random-effects model). Subgroup analyses indicated that the varying effects of isoflavones on spine BMD across trials might be associated with study characteristics of intervention duration (6 vs. 12 months), region of participant (Asian vs. Western), and basal BMD (normal bone mass vs. osteopenia or osteoporosis). No significant effects on femoral neck, hip total, and trochanter BMD were found. Soy isoflavone extract supplements increased lumbar spine BMD in menopausal women. Further studies are needed to address factors affecting the magnitudes of effect on spine and to verify the effect on hip.