Correcting Vitamin D Deficiency May Improve Glycemic Control in Type 2 Diabetes

Post on June 21, 2017 by André Broussard, D.C.

June 20, 2017

TAKE-HOME MESSAGE

  • The authors of this systematic review and meta-analysis sought to determine if vitamin D supplementation influenced glycemic control in type 2 diabetes patients. The researchers found that supplementation with vitamin D was associated with lower HbA1c levels but not lower fasting blood glucose. However, in a subgroup of patients with vitamin D deficiency at baseline, supplementation with vitamin D was associated with both lower HbA1c and fasting blood glucose. Another subgroup, patients with BMI less than 30 kg/m2, also had reductions in HbA1c levels with vitamin D supplementation.
  • The results of this study indicate that vitamin D supplementation may be useful for improving glycemic control in type 2 diabetic patients, particularly those with underlying vitamin D deficiency, and also individuals who are not obese.

 Abstract

INTRODUCTION

Low vitamin D status has been found to be associated with impaired glycemic control in patients who suffer from type 2 diabetes; however, whether vitamin D supplementation is associated with improved glycemic status remains controversial. The aim of this study was to summarize evidence from randomized controlled trials (RCTs) to assess the efficacy of vitamin D supplementation in reducing glycosylated haemoglobinA1c (HbA1c) and fasting blood glucose (FBG) levels.

MATERIALS/METHODS

We searched PubMed, Web of Science and the Cochrane Library for reports published up to March 2017. We selected parallel RCTs investigating the effect of vitamin D or vitamin D analogues on HbA1c or FBG levels in type 2 diabetes patients. Cohen’s d was calculated to represent the standardized mean difference (SMD) for each study, and the SMDs with 95%confidence intervals (CIs) were pooled using a random effects model.

RESULTS

Twenty-four studies were included that evaluated HbA1c levels and 18 studies were included that evaluated FBG levels. Meta-analyses showed that vitamin D supplementation was associated with reduced HbA1c levels (standardized mean difference (SMD) − 0.25 [− 0.45 to − 0.05]) but had no influence on FBG levels (SMD − 0.14 [− 0.31 to 0.03]). However, the subgroup analyses suggested that vitamin D supplementation was associated with reduced HbA1c levels (SMD − 0.39 [− 0.67 to − 0.10]) and FBG (SMD − 0.27 [− 0.46 to − 0.07]) among patients with 25-hydroxyvitamin D (25(OH) D) deficiency at baseline. Significantly reduced HbA1c levels were also observed in association with vitamin D supplementation in the subgroup including type 2 diabetes patients with a body mass index (BMI) < 30 kg m− 2 (SMD − 0.30 [− 0.54 to − 0.07]).

CONCLUSIONS

Vitamin D supplementation could be effective at improving glycemic control in vitamin D deficient or non-obese type 2 diabetes patients.

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