RESUMO
OBJECTIVE: To investigate the effect of soy isoflavone supplementation on bone mineral density (BMD) and markers of bone turnover in postmenopausal women. METHODS: In this randomized, placebo-controlled clinical trial, we used a crossover design to test the effect of soy isoflavone (110 mg/day) (1.3:1.0:0.22 ratio of genistein/daidzein/ glycitein) on bone formation, bone resorption, bone mineral content (BMC), and BMD for 6 months. RESULTS: Postmenopausal women (n = 19), mean age 70.6 +/- 6.3 years and mean time since menopause 19.1 +/- 5.5 years, were given isoflavone supplements for 6 months. There was a 37% decrease in urinary concentrations of type 1 collagen alpha1-chain helical peptide (HP), a marker of bone resorption, during the isoflavone supplementation compared with baseline (p < 0.05) and a significant difference in mean (SE) HP excretion levels when isoflavone was compared with placebo (43.4 +/- 5.2 vs. 56.3 +/- 7.2 microg/mmol creatinine [cr], p < 0.05). With isoflavone supplementation, mean spine BMD at L2 and L3 was significantly greater when treatment was compared with control, with a difference between means of 0.03 +/- 0.04 g and 0.03 +/- 0.04 g (p < 0.05), respectively. There were nonsignificant increases from baseline for total spine BMC (3.5%), total spine BMD (1%), total hip BMC (3.6%), and total hip BMD (1.3%) with the isoflavone treatment. CONCLUSIONS: Soy isoflavone, in isolated form, was effective in this study to significantly decrease bone resorption in postmenopausal women. Further investigation needs to be done to evaluate the long-term effects of soy isoflavone on bone mass and fracture risk.
