Vitamin D Supplementation for Prevention of Type 2 Diabetes Mellitus: To D or Not to D?

J Clin Endocrinol Metab. 2020 Dec 1;105(12):3721-3733. doi: 10.1210/clinem/dgaa594.


Context: Over the last decade, vitamin D has emerged as a risk determinant for type 2 diabetes and vitamin D supplementation has been hypothesized as a potential intervention to lower diabetes risk. Recently, several trials have reported on the effect of vitamin D supplementation on diabetes prevention in people with prediabetes.

Evidence acquisition: A comprehensive literature review was performed using PubMed, Embase, and to identify: (1) recent meta-analyses of longitudinal observational studies that report on the association between blood 25-hydroxyvitamin D (25[OH]D) level and incident diabetes, and (2) clinical trials of adults with prediabetes that have reported on the effect of vitamin D supplementation on incident diabetes.

Evidence synthesis: Longitudinal observational studies report highly consistent associations between higher blood 25(OH)D levels and a lower risk of incident diabetes in diverse populations, including populations with prediabetes. Trials in persons with prediabetes show risk reduction in incident diabetes with vitamin D supplementation. In the 3 large trials that were specifically designed and conducted for the prevention of diabetes, vitamin D supplementation, when compared with placebo, reduced the risk of developing diabetes by 10% to 13% in persons with prediabetes not selected for vitamin D deficiency.

Conclusions: Results from recent trials are congruent with a large body of evidence from observational studies indicating that vitamin D has a role in modulating diabetes risk. Participant-level meta-analysis of the 3 largest trials should provide a more refined estimate of risk reduction and identify patient populations that are likely to benefit the most from vitamin D supplementation.

Keywords: diabetes; prediabetes; prevention; type 2 diabetes; vitamin D.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Review

MeSH terms

  • Diabetes Mellitus, Type 2 / blood
  • Diabetes Mellitus, Type 2 / epidemiology
  • Diabetes Mellitus, Type 2 / prevention & control*
  • Dietary Supplements
  • Humans
  • Longitudinal Studies
  • Observational Studies as Topic / statistics & numerical data
  • Prediabetic State / drug therapy*
  • Prediabetic State / epidemiology
  • Risk Factors
  • Vitamin D / administration & dosage*
  • Vitamin D / blood


  • Vitamin D