Effects of vitamin D supplementation on blood pressure.

OBJECTIVE Inconsistent findings from epidemiological studies have continued the controversy over the role of oral vitamin D supplementation in reducing blood pressure in normotensive or hypertensive populations. METHODS We performed a literature search up to December 2009, with no restrictions. Only double-blind randomized controlled trials (RCTs) of oral vitamin D supplementation in normotensive or hypertensive individuals with blood pressure measurements were included. RESULTS From 244 retrieved papers, four RCTs involving 429 participants met our inclusion criteria for this meta-analysis. Vitamin D supplementation reduced systolic blood pressure (SBP) by 2.44 mm Hg (weighted mean difference [WMD]: -2.44, 95% confidence interval [CI]: -4.86, -0.02), but not diastolic blood pressure (DBP) (WMD: -0.02, 95% CI: -4.04, 4.01) compared with calcium or placebo. Subgroup analysis suggested that the change of blood pressure did not vary markedly across the dose of vitamin D supplementation, study length, or intervention. CONCLUSIONS Oral vitamin D supplementation may lead to a reduction in systolic blood pressure but not diastolic blood pressure. Given the small number of trials and small but statistically significant reduction in systolic blood pressure from this meta-analysis, further studies are required to confirm the magnitude of the effect of vitamin D on blood pressure reduction and define the optimum dose, dosing interval, and type of vitamin D to administer.