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.
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.
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.
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.