Phytoestrogen Intake and Risk of Ovarian Cancer: a Meta-Analysis of 10 Observational Studies

Background: Epidemiology studies have shown an inconclusive relationship between phytoestrogen intake andovarian cancer risk and there have been no relevant meta-analyses directly regarding this topic. The purpose ofthe present meta-analysis was therefore to investigate any association between phytoestrogen intake and ovariancancer in detail. Materials and
Methods: We conducted a search of PubMed, EMBASE, EBSCO, the CochraneLibrary, CNKI and Chinese Biomedical Database (up to April 2014) using common keywords for studies thatfocused on phytoestrogen and ovarian cancer risk. Study-specific risk estimates (RRs) were pooled using fixedeffect or random-effect models.
Results: Ten epidemiologic studies were finally included in the meta-analysis. Thetotal results indicated higher phytoestrogen intake was associated with a reduced ovarian cancer risk (RR, 0.70;95%CI: 0.56-0.87). The association was similar in sensitivity analysis. Meta regression analysis demonstratedsources and possibly types and regions as heterogeneous factors. Subgroup analysis of types, sources and regionsshowed that isoflavones (RR: 0.63; 95%CI: 0.46, 0.86), soy foods (RR: 0.51; 95%CI: 0.39, 0.68) and an Asian diet(RR: 0.48; 95%CI: 0.37, 0.63) intake could reduce the incidence of ovarian cancer.
Conclusions: Our findingsshow possible protection by phytoestrogens against ovarian cancer. We emphasize specific phytoestrogens fromsoy foods, but not all could reduce the risk. The habit of plentiful phytoestrogen intake by Asians is worthy torecommendation. However, we still need additional larger well designed observational studies to fully characterizeunderlying associations.