Effect of Vitamin D Supplementation on Some Inflammatory Biomarkers in Type 2 Diabetes Mellitus Subjects: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Ann Nutr Metab. 2018;73(1):62-73. doi: 10.1159/000490358. Epub 2018 Jun 26.


Background/aims: The mechanism, by which vitamin D influences inflammatory biomarkers in type 2 diabetes mellitus (T2DM), is not very well known. Thus, a meta-analysis of randomized controlled trials was conducted to assess the effect of vitamin D supplementation on some inflammatory biomarkers in T2DM subjects.

Methods: We searched randomized controlled trials from PubMed and the Cochrane Library in October 2017 and conducted a meta-analysis to evaluate the effectiveness of vitamin D supplementation on high-sensitivity C-reactive protein (hs-CRP), tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6). Either a fixed-effects or a random-effects model was used to calculate pooled effects.

Results: We identified 13 studies that met our inclusion criteria. The results indicated that the vitamin D supplementation significant decreased the hs-CRP level by 0.45 μg/mL, whereas the vitamin D supplementation did not influence the TNF-α and IL-6. Subgroup analysis showed that vitamin D significantly lowered hs-CRP by 0.34 μg/mL among trials with a daily vitamin D dose ≤4,000 IU and by 0.31 μg/mL among trials with time of vitamin D supplementation > 12 weeks.

Conclusions: Vitamin D supplementation is beneficial for the reduction of hs-CRP inT2DM subjects but does not have a significant influence on TNF-α and IL-6 in T2DM subjects.

Keywords: High-sensitivity C-reactive protein; Inflammation; Meta-analysis; Randomized controlled trials; Type 2 diabetes mellitus; Vitamin D.

Publication types

  • Meta-Analysis
  • Research Support, Non-U.S. Gov't
  • Systematic Review

MeSH terms

  • Biomarkers / blood
  • C-Reactive Protein / analysis
  • Diabetes Mellitus, Type 2 / blood*
  • Dietary Supplements*
  • Humans
  • Interleukin-6 / blood
  • Randomized Controlled Trials as Topic
  • Tumor Necrosis Factor-alpha / blood
  • Vitamin D / administration & dosage*
  • Vitamins / administration & dosage


  • Biomarkers
  • IL6 protein, human
  • Interleukin-6
  • Tumor Necrosis Factor-alpha
  • Vitamins
  • Vitamin D
  • C-Reactive Protein