Effects of Vitamin D on Blood Pressure and Cardiovascular Risk Factors: A Randomized Controlled Trial

Single-center randomized controlled trial conducted at the Medical University of Graz, Austria, in adults with arterial hypertension and low 25-hydroxyvitamin D levels (<30 ng/mL). A total of 200 participants were randomized, and 188 completed baseline and follow-up; outcome-specific vitamin D arm analyses ranged from n=83 to n=93.

Oral vitamin D3 was given as oily drops at 2800 IU/day (7 drops daily) for 8 weeks. Participants were randomized 1:1 to vitamin D3 or matching placebo.

Vitamin D3 did not lower 24-hour blood pressure or improve most cardiovascular risk markers in hypertensive adults with low vitamin D status. For 24-hour systolic BP, the treatment effect was -0.4 mmHg (95% CI -2.8 to 1.9; P = 0.712), and for 24-hour diastolic BP it was 0.2 mmHg (95% CI -1.3 to 1.7; P = 0.751). Vitamin D3 did raise 25-hydroxyvitamin D from 22.0±5.5 to 36.2±7.3 ng/mL (treatment effect 11.5; 95% CI 9.4 to 13.7; P < 0.001) and lowered parathyroid hormone (treatment effect -5.7 pg/mL; 95% CI -9.3 to -2.1; P = 0.003). No meaningful changes were seen in NT-proBNP, corrected QT interval, plasma calcium, or 24-hour urinary calcium excretion, and the trial reported a significant increase in triglycerides.

The intervention was short duration (8 weeks) and single-center, which limits assessment of longer-term cardiovascular outcomes. The cohort was described as white hypertensive patients, reducing generalizability, and several outcome analyses had smaller endpoint-specific sample sizes than the randomized total. Clinical event outcomes were not assessed, so findings are limited to surrogate cardiovascular markers.