title: Vitamin D in the prevention of acute respiratory infection: systematic review of clinical studies.
abstract: Vitamin D metabolites enhance immunity to a wide range of respiratory pathogens in vitro. Numerous observational studies have investigated whether vitamin D deficiency is a risk factor for acute respiratory infection, and a number of clinical trials of vitamin D supplementation for the prevention of acute respiratory infection have recently been conducted. Syntheses of this literature are lacking. We therefore conducted a systematic review of clinical studies investigating the association between vitamin D deficiency and susceptibility to acute respiratory infection in humans. A total of 39 studies (4 cross-sectional studies, 8 case-control studies, 13 cohort studies and 14 clinical trials) satisfying review eligibility criteria were identified. Observational studies predominantly reported statistically significant associations between low vitamin D status and increased risk of both upper and lower respiratory tract infections. Results from randomised controlled trials were conflicting however, reflecting heterogeneity in dosing regimens and baseline vitamin D status in study populations. Further trials of vitamin D supplementation for the prevention of acute respiratory infection should be conducted in populations with a high prevalence of vitamin D deficiency at baseline, using doses sufficient to induce sustained elevation of serum 25-hydroxyvitamin D concentrations, and powered to detect clinically important sub-group effects. This article is part of a Special Issue entitled 'Vitamin D Workshop'.
authors.affiliation: Queen Mary University of London, Centre for Primary Care and Public Health, Barts and The London School of Medicine and Dentistry, London E1 2AB, UK. d.a.jolliffe@qmul.ac.uk
authors.forename: David A
authors.initials: DA
authors.lastname: Jolliffe
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Griffiths
authors.forename: Adrian R
authors.initials: AR
authors.lastname: Martineau
mesh_terms: D002986:Clinical Trials as Topic; D019587:Dietary Supplements; D004198:Disease Susceptibility; D016021:Epidemiologic Studies; D006801:Humans; D012141:Respiratory Tract Infections / Q000097:blood / Q000209:etiology / Q000517:prevention & control*; D012307:Risk Factors; D014807:Vitamin D / Q000097:blood / Q000494:pharmacology*; D014808:Vitamin D Deficiency / Q000097:blood / Q000150:complications / Q000517:prevention & control
chemical_list: D014807:Vitamin D