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Diabetes Obes Metab. 2016 Apr;18(4):392-400. doi: 10.1111/dom.12625. Epub 2016 Feb 4.

Effects of vitamin D2 or D3 supplementation on glycaemic control and cardiometabolic risk among people at risk of type 2 diabetes: results of a randomized double-blind placebo-controlled trial.

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Medical Research Council Epidemiology Unit, University of Cambridge School of Clinical Medicine, Cambridge, UK.
Blizard Institute, Queen Mary University of London, London, UK.
Homerton University Hospital NHS Foundation Trust, London, UK.
Barts Healthcare NHS Trust, London, UK.



To investigate the effect of short-term vitamin D supplementation on cardiometabolic outcomes among individuals with an elevated risk of diabetes.


In a double-blind placebo-controlled randomized trial, 340 adults who had an elevated risk of type 2 diabetes (non-diabetic hyperglycaemia or positive diabetes risk score) were randomized to either placebo, 100,000 IU vitamin D2 (ergocalciferol) or 100,000 IU vitamin D3 (cholecalciferol), orally administered monthly for 4 months. The primary outcome was change in glycated haemoglobin (HbA1c) between baseline and 4 months, adjusted for baseline. Secondary outcomes included: blood pressure; lipid levels; apolipoprotein levels; C-reactive protein levels; pulse wave velocity (PWV); anthropometric measures; and safety of the supplementation.


The mean [standard deviation (s.d.)] 25-hydroxyvitamin D [25(OH)D]2 concentration increased from 5.2 (4.1) to 53.9 (18.5) nmol/l in the D2 group, and the mean (s.d.) 25(OH)D3 concentration increased from 45.8 (22.6) to 83.8 (22.7) nmol/l in the D3 group. There was no effect of vitamin D supplementation on HbA1c: D2 versus placebo: -0.05% [95% confidence interval (CI) -0.11, 0.02] or -0.51 mmol/mol (95% CI -1.16, 0.14; p = 0.13); D3 versus placebo: 0.02% (95% CI -0.04, 0.08) or 0.19 mmol/mol (95% CI -0.46, 0.83; p = 0.57). There were no clinically meaningful effects on secondary outcomes, except PWV [D2 versus placebo: -0.68 m/s (95% CI -1.31, -0.05); D3 versus placebo -0.73 m/s (95% CI -1.42, -0.03)]. No important safety issues were identified.


Short-term supplementation with vitamin D2 or D3 had no effect on HbA1c. The modest reduction in PWV with both D2 and D3 relative to placebo suggests that vitamin D supplementation has a beneficial effect on arterial stiffness.


intervention; placebo; pulse wave velocity; randomized; trial; type 2 diabetes; vitamin D2; vitamin D3

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