In patients with pre- or stage 1 hypertension and vitamin D deficiency, high-dose vitamin D supplementation was not effective at improving blood pressure, according to results of the DAYLIGHT trial presented Nov. 19 at AHA 2013.

DAYLIGHT was a prospective randomized controlled trial that studied the effects of high-dose vitamin D supplementation on blood pressure, and looked at 363 patients with pre- or stage 1 hypertension and vitamin D deficiency, who were randomized to low dose vitamin D3 (400 IU/d) and high dose vitamin D3 (4,000 IU/d).

Results showed that for the primary endpoint of 24-hour ambulatory blood pressure, at six months, Systolic BP, mm Hg, was 127 ± 10 in high dose patients, and 126 ± 9 in low dose patients (P = 0.58). Diastolic BP, mm Hg, was 77 ± 9 in high dose patients, and 76 ± 8 in low dose patients (P = 0.90). Further, the change from baseline for Systolic BP, mm Hg, was -0.8 ± 8.7 in high dose patients, and -1.6 ± 8.8 in low dose patients; and the change from baseline for Diastolic BP, mm Hg, was -1.2 ± 6.5 in high dose patients and -1.0 ± 6.8 in low dose patients. The study was stopped for futility

The authors note that "in vitamin D-deficient individuals with pre- or stage 1 hypertension, high-dose vitamin D supplementation did not improve blood pressure." They add that their findings suggest "the vitamin D and blood pressure associations seen in observational studies are not causal."

Keywords: Vitamin D Deficiency, Dietary Supplements, Blood Pressure, Medical Futility, Hypertension, Cholecalciferol