Vitamin D intake and type 2 diabetes risk: a meta-analysis of prospective cohort studies

Background The findings form studies on the relationship between vitamin D and type 2 diabetes were inconsistent. Objectives To elucidate the association between vitamin D consumption and type 2 diabetes risk by conducting a metaanalysis. Methods We conducted a systematic literature search to identify prospective cohort studies of vitamin D intake and type 2 diabetes risk prior to November 2012. Eligible studies were retrieved via both computer searches and manual review of references. The summary risk estimates were calculated based on the highest versus the lowest categories. Results Meta-analysis of 4 prospective cohort studies involving 187, 592 participants and 9, 456 incident cases showed an absence of significant association between total vitamin D intake and type 2 diabetes risk. The combined RR was 0.93 (95% CI: 0.85–1.01). The associations were similar for subgroup analyses, a combined RR respectively was 0.94 (95% CI: 0.77- 1.08), 0.91 (95% CI: 0.77-1.08), 0.93 (95% CI: 0.84-1.02), and 0.92 (95% CI: 0.84–1.01) for the intake of dietary vitamin D, supplemental vitamin D, total vitamin D in USA and total vitamin D for women only. Conclusions Our results support that there was no association between vitamin D intake and type 2 diabetes.