Selenium supplementation and the risk of type 2 diabetes mellitus: a meta-analysis of randomized controlled trials.

It is well documented that selenium (Se) is involved in the metabolism of glucose. However, whether Se supplementation could lower the risk of type 2 diabetes mellitus (T2DM) remains elusive. We aimed to evaluate the association between Se supplementation and the risk of T2DM by performing a meta-analysis. We searched the Pubmed, Embase, and Cochrane databases from January 1990 to November 2013 to identify randomized controlled trials (RCTs) that met pre-stated inclusion criteria. Reference lists of retrieved articles were also reviewed. Either a fixed-effects or, in the presence of heterogeneity, a random-effects model was used to calculate the pooled prevention effects. Four RCTs involving 20,294 participants were included in this meta-analysis. The combined relative risks (RRs) for subjects administered with Se compared with control groups were 1.09 (95 % CI: 0.99-1.20, p = 0.085). Omission of any single study did not change the overall risk estimates significantly. Meta- regression analyses showed almost no impact on the RRs of age and study length. No evidence of publication bias was observed. In conclusion, our findings do not support the routine application of Se supplementation for T2DM prevention in Caucasians. Larger studies are needed to investigate the effects of Se supplementation on T2DM prevention among various populations and further elucidate the impact of age and study length.