Effects of Phytoestrogens in Alleviating the Menopausal Symptoms: A Systematic Review and Meta-Analysis

The aim of this study was to perform a meta-analysis of high-quality, randomized, controlled trials (RCTs), to investigate the effectiveness of phytoestrogens in alleviating the menopausal symptoms (vaginal atrophy). Variety of databases including PubMed, Scopus, and Cochrane Central Register of Controlled Trials (CCRCT) were searched up to May 2015 according to the below-mentioned pre-specified search strategy and using the relevant MeSH terms. The mean difference was applied as an estimate of the main effect size. Moreover, due to the considerable heterogeneity among studies, the random-effects model was used to obtain the pooled effect size derived from primary studies. Results showed that while the standardized mean difference of vaginal cell maturation index was increased up to 0.164 percent (with the confidence interval at 95%: (-0.419-0.746), but this increase was not statistically significant (P=0.582). The absence of the publication bias was confirmed using the Egger's regression intercept test (P = 0.24). Also, meta-analysis of soybeans studies showed that while the standardized mean difference of vaginal maturation index increased 0.072% in (95% CI: -0.42 to 0.5.), this increase was not statistically significant (p = 0.777). The results confirm that soybeans and phytoestrogens have non-significant positive effects on the vaginal atrophy index. Hence, it is suggested that with regard to non-significant positive effects, non-hormonal treatments along with other treatments such as the vaginal gels and so on should be used more in cases with non-severe vaginal atrophy.