Association between Serum Selenium Level and the Presence of Diabetes Mellitus: A Meta-Analysis of Observational Studies

Background: Epidemiological studies have suggested an association between selenium (Se) and diabetes mellitus (DM). However, different studies have reported conflicting results. Therefore, we performed a comprehensive meta-analysis to clarify the impact of Se on DM. Methods: We searched the PubMed database for studies on the association between Se and DM from inception to June 2018. Results: Twenty articles evaluating 47,930 participants were included in the analysis. The meta-analysis found that high levels of Se were significantly associated with the presence of DM (pooled odds ratios [ORs], 1.88; 95% confidence interval [CI], 1.44 to 2.45). However, significant heterogeneity was found (I-2=82%). Subgroup analyses were performed based on the Se measurement methods used in each study. A significant association was found between high Se levels and the presence of DM in the studies that used blood (OR, 2.17; 95% CI, 1.60 to 2.93; I-2 =77%), diet (OR, 1.61; 95% CI, 1.10 to 2.36; I-2 =0%), and urine (OR, 1.49; 95% CI, 1.02 to 2.17; I-2 = 0%) as samples to estimate Se levels, but not in studies on nails (OR, 1.24; 95% CI, 0.52 to 2.98; I-2 = 91%). Because of significant heterogeneity in the studies with blood, we conducted a sensitivity analysis and tested the publication bias. The results were consistent after adjustment based on the sensitivity analysis as well as the trim and fill analysis for publication bias. Conclusion: This meta-analysis demonstrates that high levels of Se are associated with the presence of DM. Further prospective and randomized controlled trials are warranted to elucidate the link better.