The role of vitamin D in prevention of type 2 diabetes. A meta-analysis

Clin Nutr ESPEN. 2021 Feb:41:88-93. doi: 10.1016/j.clnesp.2020.11.005. Epub 2020 Nov 30.


Background and aims: Recently, there are evidences that have shown vitamin D homeostasis has an impact in the development of type 2 diabetes. However, still it is unclear if vitamin D supplementation reduces the risk of overt diabetes. This meta-analysis of cross-sectional studies and RCTs was conducted to evaluate the role of vitamin D in prevention of type 2 diabetes and to elucidate this controversial topic.

Methods: A systematic search for English-language literature was done via PUBMED/Medline and Google Scholar up to March 2020. Based on a fixed and random effects model, the OR, HR and 95% CI were used to evaluate the combined risk. This study followed Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) Guidelines.

Results: After eligibility assessment 10 studies with a total of 34,882 participants were included in meta-analysis. Meta-analysis of cross-sectional studies suggested that there was a statistically significant association between the vitamin D and type 2 Diabetes; the pooled OR (95%CI) was 1.77 [1.51, 2.07] (P < 0.001). Meta-analysis of RCTs have shown that there was no statistically significant association between vitamin D supplementation and prevention of type 2 Diabetes, the pooled HR (95%CI) was 0.89 [0.77, 1.02] (P = 0.08).

Conclusion: In conclusion, this meta-analysis suggests that there is association between the vitamin D and type 2 diabetes. However, the result of RCTs suggests emphasis of future studies for genetic factors such as polymorphic variants of the VDR gene as one factor in this complex process.

Keywords: 25-Hydroxyvitamin D; Meta-analysis; Type 2 diabetes; Vitamin D.

Publication types

  • Meta-Analysis

MeSH terms

  • Cross-Sectional Studies
  • Diabetes Mellitus, Type 2* / epidemiology
  • Diabetes Mellitus, Type 2* / prevention & control
  • Dietary Supplements
  • Humans
  • Vitamin D*
  • Vitamins


  • Vitamins
  • Vitamin D