Although prostate cancer is relatively rare in Asia, it accounted for 15% of total cancer incidence. Currently, 41% of global deaths from prostate cancer occur in Europe and North America. It is crucial to identify preventive measures to reduce the associated risk factors, especially those that can be performed on a daily basis with low cost. To this end Zhang and colleagues conducted a meta-analysis of epidemiologic studies to determine the relationship between soy and isoflavone (phytoestrogen) intake and prostate cancer risk. The analysis, which included 29 studies, showed that phytoestrogen intake was associated with a 23% reduction in the risk of prostate cancer. However, risk was reduced to an even greater extent when the analysis was limited to Asian studies. In this case, phytoestrogen intake was associated with a 31% reduction in risk. In contrast, among non-Asian studies, risk was reduced by only 13%. Findings in non-Asian studies are of questionable value because of the low phytoestrogen intake among Western populations. The findings of this analysis are consistent with previously published data.
Zhang M, Wang K, Chen L, Yin B, and Song Y. Is phytoestrogen intake associated with decreased risk of prostate cancer? A systematic review of epidemiological studies based on 17,546 cases. Andrology 2016.