Relationship between selenium and prostate cancer risk; systematic review and meta-analysis and meta-regression

Prostate cancer is one of the five most common cancers in men. It is suspected that selenium protect or exacerbate the risk of prostate cancer. The aim of this study was to determine the association between prostate cancer risk and selenium in the serum, toenail and supplements. So it was tried to do a systematic review and meta-analysis and meta-regression of 22 studies (5 toenail studies, 14 serum studies and 3 supplements studies) in order to obtain detailed results of these studies’ data. Meta-regression results showed that location of study (p value <0.001), type of study (p value = 0.04) and age (p value =0.008) have significant effects on heterogeneity. There was no publication bias in studies (Begger's test: z-value = 1.98; P value=0.067). In general, unlike selenium supplements [OR=0.86 (CI: 0.7-1.06, P value=0.15], selenium increase in serum [OR=0.76 (0.59-0.99, P value=0.04] and toenail [OR=0.58 (0.4-0.86, P value=0.01] significantly decreased the risk of prostate cancer by %24 and 42 %. In general, the odds ratio between prostate cancer caused by selenium in the random effect model OR: 0.71 (CI: 0.59- 0.86%, P value <0.001) and heterogeneity was moderate (I2 = 70.6%, P value <0.001). The results of this study supported the lowering effect of selenium in serum and toenail on the risk of prostate cancer.