The effect of vitamin D supplementation on glucose metabolism in type 2 diabetes mellitus: A systematic review and meta-analysis of intervention studies

Clare Lee, Geetha Iyer, Yang Liu, Rita R. Kalyani, N'Dama Bamba, Colin B. Ligon, Sanskriti Varma, Nestoras Nicolas Mathioudakis

Research output: Contribution to journalArticle


Aims: We aimed to assess whether vitamin D supplementation improves glucose metabolism in adults with type 2 diabetes. Methods: PubMed and Cochrane database were searched up to July 1st 2016 for randomized controlled trials that assessed the relationship between vitamin D supplementation and glucose metabolism (change in hemoglobin A1C (HbA1C) and fasting blood glucose (FBG)) among adults with type 2 diabetes. Results: Twenty nine trials (3324 participants) were included in the systematic review. Among 22 studies included in the meta-analysis, 19 reported HbA1C, 16 reported FBG outcomes and 15 were deemed poor quality. There was a modest reduction in HbA1C (-0.32% [-0.53 to -0.10], I 2 =91.9%) compared to placebo after vitamin D supplementation but no effect on FBG (-2.33mg/dl [-6.62 to 1.95], I 2 =59.2%). In studies achieving repletion of vitamin D deficiency (n =7), there were greater mean reductions in HbA1C (-0.45%, [-1.09 to 0.20]) and FBG (-7.64mg/dl [-16.25 to 0.97]) although not significant. Conclusions: We found a modest reduction of HbA1C after vitamin D treatment in adults with type 2 diabetes albeit with substantial heterogeneity between studies and no difference in FBG. Larger studies are needed to further evaluate the glycemic effects of vitamin D treatment especially in patients with vitamin D deficiency.

Original languageEnglish (US)
JournalJournal of Diabetes and its Complications
Publication statusAccepted/In press - Jan 11 2017



  • Glucose metabolism
  • Randomized controlled trials
  • Systematic review
  • Type 2 diabetes
  • Vitamin D

ASJC Scopus subject areas

  • Internal Medicine
  • Endocrinology, Diabetes and Metabolism
  • Endocrinology

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