Effect of Vitamin D on Blood Pressure and Hypertension in the General Population: An Update Meta-Analysis of Cohort Studies and Randomized Controlled Trials.

Background The effect of vitamin D supplementation on blood pressure has been explored in previous meta-analyses, but whether the association is causal in the general population is still unknown. We evaluated the association comprehensively and quantitatively. Methods We searched PubMed and Embase for relevant cohort studies and randomized controlled trials (RCTs). We used a 2-step generalized least-squares method to assess the dose-response association of circulating 25-hydroxyvitamin D (25[OH]D) and hypertension and a fixed-effects model to pool the weighted mean differences (WMDs) and corresponding 95% confidence intervals (95% CIs) of blood pressure across RCTs. Results We identified 11 cohort studies and 27 RCTs, with 43,320 and 3,810 participants, respectively. The dose-response relationship between circulating 25(OH)D levels and hypertension risk was approximately L-shaped (P-nonlinearity = .04), suggesting that the risk of hypertension increased substantially below 75 nmol/L as 25(OH)D decreased, but it remained significant over the range of 75-130 nmol/L. However, pooled results of RCTs showed that there was no significant reduction in systolic blood pressure (WMD, -0.00 mm Hg; 95% CI, -0.71 to 0.71) or diastolic blood pressure (WMD, 0.19 mm Hg; 95% CI, -0.29 to 0.67) after vitamin D intervention. Conclusions The results of this meta-analysis indicate that supplementation with vitamin D does not lower blood pressure in the general population. RCTs with long-term interventions and a sufficient number of participants who have low levels of vitamin D are needed to validate these findings.