Vitamin D supplementation does not improve CVD risk factors in vitamin D-insufficient subjects
What this study found
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.
- Study & population
- Double-blind randomized controlled trial in adults with vitamin D insufficiency recruited from the Tromsø region in Northern Norway.
- Intervention
- 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.
- Key limitation
- The intervention lasted only 4 months, which may be too short to detect changes in cardiovascular outcomes.
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Open PDFOriginal abstract
Objective Low serum 25(OH)D levels are associated with cardiovascular disease (CVD) and some of its risk factors. However, in interventional studies, the effects of vitamin D supplementation have been uncertain, possibly due to inclusion of vitamin D-sufficient subjects. Our aim was therefore to examine effects of vitamin D supplementation on CVD risk factors in vitamin D-insufficient subjects. Design Double-blinded randomized controlled trial. Methods A 4-month interventional study with high-dose vitamin D (100,000 IU loading dose, followed by 20,000 IU/week) or placebo with measurements of blood pressure, lipids (total-, LDL- and HDL-cholesterol, triglycerides, apolipoproteins A1 and B), and glucose metabolism parameters (blood glucose, HbA1c, serum human receptors for advanced glycation end products (sRAGE), insulin, C-peptide and HOMA-IR). Results A total of 422 subjects with mean serum 25(OH)D level 34 nmol/L were included, with 411 subjects completing the study. Serum 25(OH)D levels increased with 56 nmol/L and decreased with 4 nmol/L in the vitamin D and placebo group, respectively. We found no statistically significant differences between the two groups in any of the measured CVD risk factors, except for a minor increase in sRAGE in the vitamin D group. Stratified analyses of subjects with low baseline serum 25(OH)D levels alone, or combined with blood pressure, lipid and HOMA-IR values above the median for the cohort, did not skew the results in favour of vitamin D supplementation. Conclusion Supplementation with vitamin D in subjects with baseline vitamin D insufficiency does not improve CVD risk factor profile.