Effects Of Vitamin A Supplementation On Asthma, Allergy And Lung Function: Systematic Review And Meta-Analysis Of Human Models

Objective To assess the evidence of therapeutic effects of vitamin A on asthma in human models.Methods Databases (Medline, Embase, EBSCO, Web of Science) were searched for collecting the randomized controlled trials (RCTs) of the effects of vitamin A supplementation on asthma, wheeze, allergy and lung function in human models from inception to February 28th,2015. We also undertook handsearching of associated journal as well as references of RCTs. Studies were critically appraised, and meta-analyses were then performed using RevMan 5.3 software.Results(1) 10 eligible RCTs were identified comprising a total of 6354 subjects. Part of between-study heterogeneity was large. Experimental group was supplemented with oral vitamin A (VA) or β-carotene (βC), while controlled intervention was oral placebo without it. Results of meta-analysis showed that, administration of VA/βC reduced the risk of children’s atopy [RR=1.65,95%CI(1.10,2.47), P=0.01] and improved lung function [SMD=0.21,95%CI(0.08,0.33), P=0.002].(2) While significant differences were neither found in delayed-type hypersensitivity nor in wheezing in previous year between the VA/βC group and the control group.Conclusion(1) Administration of VA/βC significantly reduced the risk of children’s atopy and improved lung function in asthma patients as well as healthy people, especially when early intervention, which indicated that VA might partially protect asthma from occurrence and development.(2) There were no significant differences found in wheezing in previous year or in delayed-type hypersensitivity between VA/βC group and placebo group.(3) Based on the current evidence, treatment with VA shows controversial therapeutic effects on asthma. So far, the clinical results should be interpreted with caution while concerning the internal and external validity of the studies, so as to design clinical trials with high quality.