Abstract
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.