Soy isoflavones prevent bone resorption and loss, a systematic review and meta-analysis of randomized controlled trials

<b>Background:</b> Osteoporosis is a common bone disease characterized by reduced bone mass resulting from continuous bone resorption. <b>Methods:</b> PubMed, Scopus, and Embase were searched to find published trials on the effect of soy isoflavones on bone mineral density (BMD) and bone turnover markers (bone-specific alkaline phosphatase, osteocalcin, osteoprotegerin, pyridinoline, deoxypyridinoline, C-telopeptide, and N-telopeptide). Random-effects inverse-variance model was used to calculate the pooled effects. <b>Results:</b> A total of 5313 articles were found, screened, and assessed for eligibility, and finally 52 trials were included in the meta-analysis. Consumption of soy isoflavones caused significant improvement in BMD of lumbar spine (mean difference (MD) = 0.76%; 95% CI: 0.09, 1.42%; <i>p</i> = 0.03), hip (MD = 0.22%; 95% CI: 0.02, 0.42%; <i>p</i> = 0.04), and femoral neck (MD = 2.27%; 95% CI: 1.22, 3.31%; <i>p</i> p p p = 0.04) were favorably affected by isoflavones while osteocalcin and bone alkaline phosphatase did not change. Subgroup analysis of bone markers showed that in overweight/obese individuals and dosages &lt;90 mg/day, isoflavones are more effective. <b>Conclusions:</b> Soy isoflavones prevent osteoporosis-related bone loss in any weight status or treatment duration. They increase BMD in normal weight subjects and diminish bone resorption in overweight/obese individuals. Although bone resorption may be decelerated over short-term isoflavone consumption, periods longer than a year are probably needed to affect BMD. Isoflavones also appear benefits on bone in any dose or subjects’ ethnicity.