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Tai and colleagues [1] have recently reported that treatment with 300 mg/day of isoflavones (aglycone equivalents) (172.5 mg genistein + 127.5 mg daidzein) for 2 years failed to prevent lumbar spine and total proximal femur bone mineral density (BMD) from declining, as compared with the placebo group. This randomized, double-blind, two-arm-designed study was conducted in a clinical sample of 431 postmenopausal women aged 45–65 years in three centers of Taipei (Taiwan). Each participant also ingested 600 mg of calcium and 125 IU of vitamin D per day. The BMD of the lumbar spine and total proximal femur were measured using dual-energy X-ray absorptiometry at baseline and every half-year thereafter. Serum bone-specific alkaline phosphatase, urinary N-telopeptide of type 1 collagen/creatinine, and other safety assessments were examined regularly. Serum concentrations of isoflavone metabolites, genistein and daidzein, in the intervention group were remarkably elevated following intake of isoflavones ([i]p[/i] < 0.001). However, differences in the mean percentage changes of BMD throughout the treatment period were not statistically significant (lumbar spine, [i]p[/i] = 0.42; total femur, [i]p[/i] = 0.39) between the isoflavone and placebo groups. A significant time trend of bone loss was observed at both sites following repeated measurement of BMD ([i]p[/i] < 0.001). Differences in bone marker levels were not significant between the two treatment groups. The authors concluded that treatment with 300 mg/day isoflavones (aglycone equivalents) failed to prevent a decline in BMD in the lumbar spine or total femur compared with the placebo group.

Author(s)

  • Camil Castelo-Branco
    Ob Gyn Senior Consultant, Hospital Clínic Barcelona, and Full Professor, University of Barcelona, Spain

Citations

  1. Tai TY, Tsai KS, Tu ST, et al. The effect of soy isoflavone on bone mineral density in postmenopausal Taiwanese women with bone loss: a 2-year randomized double-blind placebo-controlled study. Osteoporos Int 2011 Sep 8. Epub ahead of print
    http://www.ncbi.nlm.nih.gov/pubmed/21901480
  2. Taku K, Melby MK, Kurzer MS, Mizuno S, Watanabe S, Ishimi Y. Effects of soy isoflavone supplements on bone turnover markers in menopausal women: systematic review and meta-analysis of randomized controlled trials. Bone 2010;47:41323.
    http://www.ncbi.nlm.nih.gov/pubmed/20452475
  3. Taku K, Melby MK, Takebayashi J, et al. Effect of soy isoflavone extract supplements on bone mineral density in menopausal women: meta-analysis of randomized controlled trials. Asia Pac J Clin Nutr 2010;19:3342.
    http://www.ncbi.nlm.nih.gov/pubmed/20199985
  4. Kenny AM, Mangano KM, Abourizk RH, et al. Soy proteins and isoflavones affect bone mineral density in older women: a randomized controlled trial. Am J Clin Nutr 2009;90:23442.
    http://www.ncbi.nlm.nih.gov/pubmed/19474141
  5. Alekel DL, Van Loan MD, Koehler KJ, et al. The soy isoflavones for reducing bone loss (SIRBL) study: a 3-y randomized controlled trial in postmenopausal women. Am J Clin Nutr 2010;91:21830.
    http://www.ncbi.nlm.nih.gov/pubmed/19906801
  6. Zhang X, Shu XO, Li H, et al. Prospective cohort study of soy food consumption and risk
    http://www.ncbi.nlm.nih.gov/pubmed/16157834
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