1. Vitamin D deficiency is associated with high blood pressure and cardiovascular disease.
2. Ameliorating vitamin D deficiency through supplementation did not lower blood pressure in this study.
Evidence Rating Level: 1 (Excellent)
Study Rundown: Previous work has demonstrated that low serum levels of vitamin D are associated with elevated blood pressure. Vitamin D receptors are found on smooth muscle and endothelial cells, which represents a plausible mechanism through which vitamin D might act on the vascular system. This meta-analysis sought to address whether or not vitamin D supplementation in patients deficient in vitamin D would lower blood pressure. Through analysis of several randomized clinical trials, this study did not find any anti-hypertensive effect of vitamin D supplementation.
Limitations to this paper include the caliber of the studies included in the meta-analysis, as most were single-center trials that recruited less than 1000 patients. It is also indeterminate what the optimal dose might be of vitamin D supplementation. The authors suggest that many of the studies this paper makes reference to were using doses too low for adequate serum levels. However, excess vitamin D further can result in toxicity if ingested in very high doses, resulting in renal calculi, gastrointestinal symptoms, or even risk of cardiac events.
Relevant Reading: Effect of Vitamin D Supplementation on Blood Pressure
In-Depth [meta-analysis]: The authors used MEDLINE and other sources to identify clinical trials containing search terms related to vitamin D and hypertension. Studies that measured baseline 25-hydroxyvitaminD (25OHD) versus blood pressure or surrogate markers of cardiovascular risk were included in study. All trials had an intervention arm of minimum 4 weeks of treatment with vitamin D2, vitamin D3, calcitriol, paricalcitol, or doxerocalciferol. Forty-six trials, including a total of 4,541 patients, were ultimately included in analysis. The primary outcome was change in office-measured systolic and diastolic blood pressure readings from baseline through follow-up.
Both individual (for 27 trials) and trial data were analyzed. At the trial level, no effect of vitamin D supplementation was seen on either systolic (effect size 0.0; 95%CI −0.8 to 0.8 mm Hg; p = 0.97) or diastolic (effect size −0.1; 95%CI −0.6 to 0.5 mmHg; p = 0.84) blood pressures. Similar results were found upon analyzing individual data. Subgroup analyses were also unrevealing, and did not suggest any particular groups that would benefit more than others from supplementation.
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