Objectives Vitamin D
insufficiency has been linked to hypertension
and cardiovascular events in observational studies. It is unclear whether vitamin D
supplementation can reduce blood pressure
, and, if so, by how much.
We performed a systematic review
and meta-analysis to examine whether vitamin D
reduces blood pressure
. Databases including MEDLINE, EMBASE, the Cumulative Index to Nursing and Allied Health Literature and the Cochrane library were searched, supplemented by searches of grey literature, unpublished trials and references from included studies. Studies were assessed by two reviewers independently according to a prespecified protocol. Interventions included activated vitamin D
, unactivated vitamin D2 and D3 and ultraviolet B radiation.
Eleven randomized, controlled trials fulfilled the inclusion criteria. Studies were small and of variable methodological quality. Mean baseline blood pressure
was more than 140/90 mmHg in eight studies. Meta-analysis of these eight studies showed a nonsignificant reduction in systolic blood pressure
in the vitamin D
group compared with placebo [−3.6 mmHg, 95% confidence interval (CI) −8.0 to 0.7]. A small, statistically significant reduction was seen in diastolic blood pressure
(−3.1 mmHg, 95% CI −5.5 to −0.6). Subgroup analysis suggested that unactivated vitamin D
produced a greater fall in systolic blood pressure
than activated vitamin D
(−6.2 mmHg, 95% CI −12.32 to −0.04, vs. +0.7 mmHg, 95% CI −4.8 to 6.2). No reduction in blood pressure
was seen in studies examining patients who were normotensive at baseline.
We found weak evidence to support a small effect of vitamin D
on blood pressure
in studies of hypertensive patients.