Soy isoflavone intake increases bone mineral density in the spine of menopausal women: meta-analysis of randomized controlled trials

Abstract

Background & aims: The effects of isoflavones on bone loss appear inconsistent in randomized controlled trials. Therefore, we used a statistical method of combining these diverse data to clarify the effects of soy isoflavone intake on spine bone loss.

Methods: We identified randomized controlled trials related to the effects of soy isoflavone intake on spine bone mineral density or spine bone mineral content and performed meta-analysis with Review Manager 4.2 software.

Results: Ten studies with a total of 608 subjects were selected for meta-analysis. The spine bone mineral density in subjects who consumed isoflavones increased significantly by 20.6 mg/cm(2) (95% confidence interval: 4.5-36.6 mg/cm(2)) in comparison to that in subjects who did not consume isoflavones. Isoflavone intake vs placebo intake increased spine bone mineral content by 0.93 g (95% confidence interval: -0.37 to 2.24 g) with borderline significance. Increases in the spine bone mineral density with isoflavone intake of more than 90 mg/day and with treatment lasting 6 months were 28.5mg/cm(2) (95% confidence interval: 8.4-48.6 mg/cm(2)) and 27 mg/cm(2) (95% confidence interval: 8.3-45.8 mg/cm(2)), respectively.

Conclusions: Isoflavone intervention significantly attenuates bone loss of the spine in menopausal women. These favorable effects become more significant when more than 90 mg/day of isoflavones are consumed. And soy isoflavone consumption for 6 months can be enough to exert beneficial effects on bone in menopausal women.