Vitamin D and cardiovascular outcomes: A systematic review and meta-analysis

Context: Several studies found association between vitamin D levels and hypertension, coronary artery calcification, and heart disease. Objective: The aim of this study was to summarize the evidence on the effect of vitamin D on cardiovascular outcomes. Design and Methods: We searched electronic databases from inception through August 2010 for randomized trials. Reviewers working in duplicate and independently extracted study characteristics, quality, and the outcomes of interest. Random-effects meta-analysis was used to pool the relative risks (RR) and the weighted mean differences across trials. Results: We found 51 eligible trials with moderate quality. Vitamin D was associated with non-significant effects on the patient-important outcomes of death [RR, 0.96; 95% confidence interval (CI), 0.93, 1.00; P = 0.08], myocardial infarction (RR, 1.02; 95% CI, 0.93, 1.13; P = 0.64), and stroke (RR, 1.05; 95% CI, 0.88, 1.25; P = 0.59). These analyses were associated with minimal heterogeneity. There were no significant changes in the surrogate outcomes of lipid fractions, glucose, or diastolic or systolic blood pressure. The latter analyses were associated with significant heterogeneity, and the pooled estimates were trivial in absolute terms. Conclusions: Trial data available to date are unable to demonstrate a statistically significant reduction in mortality and cardiovascular risk associated with vitamin D. The quality of the available evidence is low to moderate at best.