Vitamin D may not protect against mortality and cardiovascular risk, according to the results of a systematic review and meta-analysis reported in the July issue of the Journal of Clinical Endocrinology & Metabolism.

”Several studies found association between vitamin D levels and hypertension, coronary artery calcification, and heart disease,” write Mohamed B. Elamin, from the Knowledge and Evaluation Research Unit at Mayo Clinic in Rochester, Minnesota, and colleagues. ”The aim of this study was to summarize the evidence on the effect of vitamin D on cardiovascular outcomes.”

The reviewers searched electronic databases for relevant randomized trials reported from inception through August 2010. Both independently and in duplicate, they extracted data regarding study characteristics, methodologic quality, and pertinent study endpoints. Relative risks (RRs) and weighted mean differences across trials were pooled with random-effects meta-analysis.

The literature search yielded 51 trials of moderate quality meeting inclusion criteria. Pooling across studies showed that the effects of vitamin D were nonsignificant on endpoints of death (RR, 0.96; 95% confidence interval [CI], 0.93 – 1.00; P = .08), myocardial infarction (RR, 1.02; 95% CI, 0.93 – 1.13; P = .64), and stroke (RR, 1.05; 95% CI, 0.88 – 1.25; P = .59). There was minimal heterogeneity in these analyses.

Surrogate markers of lipid fractions, glucose levels, or diastolic or systolic blood pressure did not change significantly with vitamin D, but there was significant heterogeneity in these analyses, and the pooled estimates were trivial in absolute terms.

”Trial data available to date are unable to demonstrate a statistically significant reduction in mortality and cardiovascular risk associated with vitamin D,” the review authors write. ”The quality of the available evidence is low to moderate at best.”

Limitations of this review and meta-analysis include the fact that many of the included studies were not designed to evaluate cardiovascular outcomes; possible publication and reporting biases; heterogeneity in some of the analyses, causing the overall evidence to be of low to moderate quality; and possible confounding baseline cardiac risk factors.

”The practice implications of this systematic review indicate that recommending vitamin D to patients to reduce cardiovascular risk is not consistent with the current evidence,” the study authors conclude. ”Individuals will require the age-and sex-appropriate daily intake of vitamin D and may require additional supplementation for other indications such as bone health, but not for cardiovascular risk reduction. The accompanying guideline document developed by the task force of the Endocrine Society will provide additional practical advice and detailed recommendations regarding vitamin D supplementation.”

Source: J Clin Endocrinol Metab. 2011;96:1931-1942.

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