Effect of vitamin D supplementation on oral glucose tolerance in individuals with low vitamin D status and increased risk for developing type 2 diabetes (EVIDENCE): A double-blind, randomized, placebo-controlled clinical trial

Diabetes Obes Metab. 2017 Jan;19(1):133-141. doi: 10.1111/dom.12794. Epub 2016 Nov 9.


Aims: Low serum 25-hydroxyvitamin-D (25(OH)D) concentrations are associated with insulin resistance, β-cell dysfunction and type 2 diabetes. We conducted a 24-week double-blind, randomized, placebo-controlled trial to examine the effect of 28 000 IU of vitamin D3 once weekly on plasma glucose after a 2 hour-75 g oral glucose tolerance test (2hrPC glucose), insulin sensitivity and β-cell function.

Study design and methods: A total of 71 participants with serum 25(OH)D ≤65 nmol/L, impaired fasting glucose and elevated glycated hemoglobin were randomly assigned to receive 28 000 IU of vitamin D3 (VitD; n = 35) or placebo (n = 36) in cheese once weekly for 24 weeks. The primary outcome was the change in 2hPC glucose. Secondary outcomes were fasting glucose, fasting and postprandial insulin, indices of insulin sensitivity and β-cell function, glycated hemoglobin and lipid profile. Participants underwent an oral glucose tolerance test to determine 2hPC glucose.

Results: Mean baseline serum 25(OH)D was 48.1 and 47.6 nmol/L in the VitD and placebo groups, respectively. Serum 25(OH)D significantly increased to 98.7 nmol/L (51 nmol/L increase; P < .0001) in the VitD group. No significant differences in fasting ( P = .42) or 2hPC glucose ( P = .55) or other indices of glucose metabolism, including β-cell function and insulin sensitivity, were observed between groups. A subgroup analysis of individuals with 25(OH)D < 50 nmol/L and prediabetes did not change these results. The VitD group exhibited a significant reduction in LDL cholesterol (-0.27 vs 0.01 mmol/L, P = .03).

Conclusion: Weekly doses of vitamin D3 in individuals with suboptimal vitamin D levels who were at risk for type 2 diabetes did not improve oral glucose tolerance or markers of glycaemic status.

Keywords: beta cell; clinical trial; dietary; insulin resistance; intervention; randomized trial.

Publication types

  • Multicenter Study
  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Blood Glucose / metabolism*
  • Cholecalciferol / therapeutic use*
  • Cholesterol, LDL / metabolism
  • Diabetes Mellitus, Type 2 / epidemiology
  • Diabetes Mellitus, Type 2 / metabolism
  • Dietary Supplements
  • Double-Blind Method
  • Fasting
  • Female
  • Glucose Tolerance Test
  • Glycated Hemoglobin / metabolism
  • Humans
  • Insulin / metabolism
  • Insulin Resistance*
  • Insulin-Secreting Cells / metabolism
  • Male
  • Middle Aged
  • Postprandial Period
  • Prediabetic State / epidemiology
  • Prediabetic State / metabolism*
  • Risk
  • Vitamin D / analogs & derivatives
  • Vitamin D / metabolism
  • Vitamin D Deficiency / drug therapy*
  • Vitamin D Deficiency / epidemiology
  • Vitamin D Deficiency / metabolism
  • Vitamins / therapeutic use*


  • Blood Glucose
  • Cholesterol, LDL
  • Glycated Hemoglobin A
  • Insulin
  • Vitamins
  • hemoglobin A1c protein, human
  • Vitamin D
  • Cholecalciferol
  • 25-hydroxyvitamin D