Effect of vitamin D supplementation on glycaemic control and insulin resistance: a systematic review and meta‐analysis

Abstract

Aims To systematically review the evidence for the effect of vitamin D supplementation on glycaemia, insulin resistance, progression to diabetes and complications of diabetes.Methods Systematic review and meta-analysis. We searched databases including MEDLINE, EMBASE and the Cochrane Library for randomized controlled trials comparing vitamin D or analogues with placebo. We extracted data on fasting glucose, glycaemic control, insulin resistance, insulin ⁄ C-peptide levels, micro-and macrovascular outcomes and progression from non-diabetes to diabetes. Studies were assessed independently by two reviewers according to a pre-specified protocol.Results Fifteen trials were included in the systematic review. Trial reporting was of moderate, variable quality. Combining all studies, no significant improvement was seen in fasting glucose, HbA 1c or insulin resistance in those treated with vitamin D compared with placebo. For patients with diabetes or impaired glucose tolerance, meta-analysis showed a small effect on fasting glucose ()0.32 mmol ⁄ l, 95% CI )0.57 to )0.07) and a small improvement in insulin resistance (standard mean difference )0.25, 95% CI )0.48 to )0.03). No effect was seen on glycated haemoglobin in patients with diabetes and no differences were seen for any outcome in patients with normal fasting glucose. Insufficient data were available to draw conclusions regarding micro-or macrovascular events; two trials failed to show a reduction in new cases of diabetes in patients treated with vitamin D.Conclusions There is currently insufficient evidence of beneficial effect to recommend vitamin D supplementation as a means of improving glycaemia or insulin resistance in patients with diabetes, normal fasting glucose or impaired glucose tolerance.Diabet. Med. 29, e142-e150 (2012)

Maternal vitamin D status in Type 1 diabetic pregnancy: Impact on neonatal vitamin D status and association with maternal glycaemic control

“…With respect to a causal link between vitamin D repletion and improved glucose homeostasis, limited studies have reported substantial improvements in glycaemic control (HbA 1c levels) in T1DM patients who achieved higher circulating 25OHD levels via supplementation [36,37]. The results of a recent systematic review suggest a weak effect of vitamin D supplementation in reducing fasting glucose and improving insulin resistance in patients with T2DM or impaired glucose tolerance [38]. The magnitude of the reduction in fasting glucose seen in this analysis was small leading the authors to conclude that, given that HbA 1c did not change in patients with impaired glucose tolerance or T2DM, this is of debatable clinical significance.…”

MANAGEMENT OF ENDOCRINE DISEASE: The effect of vitamin D supplementation on glycaemic control in patients with type 2 diabetes mellitus: a systematic review and meta-analysis

“…For studies lacking a reported standard deviation of change in outcome between baseline and follow-up, we derived standard deviation of change as the mean of the baseline and follow-up standard deviations for each treatment group. This method was used successfully in the metaanalysis from George et al performed on this subject (14).…”

Effect of a Randomised Controlled Vitamin D Trial on Insulin Resistance and Glucose Metabolism in Patients with Type 2 Diabetes Mellitus

“…Whether vitamin D can also aff ect the human β-cell has been subject to several studies, including interventional trials. A meta-analysis of vitamin D supplementation of patients with type 2 diabetes has recently summarised 15 trials that had included patients for a controlled intervention with vitamin D, its metabolites and placebo, and studied fasting glucose, HbA1c as well as parameters of insulin resistance [ 40 ] . The conclusion of their summary was that insuffi cient evidence supported a recommendation for vitamin D supplementation for improving glucose metabolism or insulin action in patients with diabetes or prediabetes.…”