No Effect of High-Dose Vitamin D Supplementation on Glycemic Status or Cardiovascular Risk Factors in Subjects With Prediabetes

Study answer

What this study found

High-dose vitamin D did not improve glycemic status or cardiovascular risk factors over 1 year in adults with prediabetes. Serum 25(OH)D rose substantially in the vitamin D group, increasing by 45.8 ± 24.2 nmol/L versus 3.4 ± 16.9 nmol/L with placebo (P < 0.001), and PTH fell by 0.5 pmol/L versus a 0.2 pmol/L increase with placebo (P < 0.001). Total cholesterol fell by 0.16 mmol/L and LDL cholesterol by 0.17 mmol/L versus placebo (P < 0.05), but HDL cholesterol decreased and the TC/HDL ratio did not differ significantly. There were no significant between-group differences in glycemic…

Study & population

Randomized, placebo-controlled trial in adults with prediabetes, defined by impaired fasting glucose and/or impaired glucose tolerance, without diabetes.

Intervention

The active regimen was oral cholecalciferol (vitamin D3) 20,000 IU per week, given as identical-looking capsules for 6 months, compared with placebo.

Key limitation

The trial showed no benefit on the main clinical outcomes despite clear biochemical repletion, which limits clinical interpretability.

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Original abstract