title: Effect of vitamin D on blood pressure: a systematic review and meta-analysis.
abstract: OBJECTIVE
  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and Allied Health Literature and the Cochrane library were searched, supplemented by searches of grey literature, unpublished trials and references from included studies.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.
  
  
  CONCLUSIONS
  We found weak evidence to support a small effect of vitamin D on blood pressure in studies of hypertensive patients.
authors: 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. m.witham@dundee.ac.uk
authors: Miles D
authors: MD
authors: Witham
authors: M Adnan
authors: MA
authors: Nadir
authors: Allan D
authors: AD
authors: Struthers
mesh_terms: D001794:Blood Pressure / Q000187:drug effects*; D006801:Humans; D006973:Hypertension / Q000150:complications / Q000188:drug therapy*; D014807:Vitamin D / Q000008:administration & dosage*; D014808:Vitamin D Deficiency / Q000150:complications / Q000188:drug therapy*; D014815:Vitamins / Q000008:administration & dosage*
chemical_list: D014815:Vitamins; D014807:Vitamin D