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.
Methods: 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and Allied Health Literature and the Cochrane library were searched, supplemented by searches of grey literature, unpublished trials and references from included studies.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.
Results: 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.
Conclusion: We found weak evidence to support a small effect of vitamin D on blood pressure in studies of hypertensive patients.
aSection of Ageing and Health, Scotland
bDepartment of Clinical Pharmacology, Centre for Cardiovascular and Lung Biology, Division of Medical Sciences, University of Dundee, Ninewells Hospital and Medical School, Dundee, Scotland
Received 26 February, 2009
Revised 8 May, 2009
Accepted 4 June, 2009
Correspondence to Miles D. Witham, BM, BCh, PhD, Clinical Lecturer, Section of Ageing and Health, Centre for Cardiovascular and Lung Biology, Division of Medical Sciences, University of Dundee, Ninewells Hospital and Medical School, Dundee DD1 9SY, Scotland Tel: +44 01382 632436; fax: +44 01382 660675; e-mail: email@example.com