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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Forouhi, NG 
Menon, RK 
Sharp, SJ 
Mannan, N 
Timms, PM 

AIMS: To investigate the effect of short-term vitamin D supplementation on cardiometabolic outcomes among individuals with an elevated risk of diabetes. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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, 25-Hydroxyvitamin D 2, Adult, Aged, Calcifediol, Cardiovascular Diseases, Cholecalciferol, Cohort Studies, Diabetes Mellitus, Type 2, Dietary Supplements, Double-Blind Method, England, Ergocalciferols, Feasibility Studies, Female, Follow-Up Studies, Glycated Hemoglobin, Humans, Male, Middle Aged, Pulse Wave Analysis, Risk, Vascular Stiffness
Journal Title
Diabetes Obes Metab
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Medical Research Council (MC_UU_12015/4)
Medical Research Council (MC_UU_12015/5)
Medical Research Council (MC_U106179474)
The trial was jointly sponsored by Queen Mary University of London and the Medical Research Council Epidemiology Unit at Cambridge. The trial was funded from a block grant from the NHS Tower Hamlets Primary Care NHS Trust and East London CLRN, and from MRC Epidemiology Unit core funding (MC_UP_A100_1003, MC_U106179474, MC_UU_12015/5 and MC_UU_12015/4).