Vitamin D supplementation does not improve CVD risk factors in vitamin D-insufficient subjects

Double-blind randomized controlled trial in adults with vitamin D insufficiency recruited from the Tromsø region in Northern Norway. The study randomized 422 participants in a 1:1 ratio; 211 were assigned to vitamin D and 211 to placebo, with the vitamin D arm reporting 208 completers. Baseline cohort characteristics included a mean age of 50 years, BMI of 28 kg/m^2, and mean serum 25(OH)D of 34 nmol/L.

Participants in the active arm received oral cholecalciferol capsules: a 100,000 IU loading dose (five 20,000 IU capsules), followed by 20,000 IU per week for 4 months. The comparator was identical placebo capsules containing arachis oil.

Vitamin D supplementation did not improve cardiovascular risk factors in vitamin D-insufficient adults. Serum 25(OH)D rose by 56 nmol/L in the vitamin D group and fell by 4 nmol/L in the placebo group, but there were no statistically significant between-group differences in blood pressure, lipids, or glucose metabolism measures. A minor increase in sRAGE was observed, including a significant delta value in the specified subgroup (P < 0.05), but subgroup analyses did not show overall benefit. No serious study-related side effects were reported, although two participants developed hypercalcemia.

The intervention lasted only 4 months, which may be too short to detect changes in cardiovascular outcomes. Generalizability is limited to vitamin D-insufficient adults from one northern Norwegian region, and arm-specific ethnicity, diet, and physical activity data were not reported. The trial also yielded no supportive benefit in subgroup analyses, despite clear biochemical repletion.