RESUMO
CONTEXT: Observational studies have suggested a relationship between vitamin D status and asthma-related respiratory outcomes. The benefit of vitamin D supplementation for pulmonary function, symptoms and exacerbations is not well established. OBJECTIVE: To systematically review paediatric clinical trials investigating the role of vitamin D on asthma-related respiratory outcomes. DATA SOURCES: MEDLINE, EMBASE and CENTRAL were searched until January 2014. No date or language restrictions. STUDY SELECTION: Clinical trials reporting asthma-related respiratory outcomes following vitamin D administration at a dose equal or greater than 500 IU per day were included and reviewed independently by two authors for full systematic review eligibility. DATA EXTRACTION: Two reviewers independently extracted and verified pre-defined data fields. RESULTS: We identified five studies that met study eligibility and assessed final data synthesis. The median trial size was 48 participants (range 17-430) and the average daily dose of cholecalciferol ranged from 500 to 2000 IU/day. Overall study methodological quality was high, but some heterogeneity in population and vitamin D dosing regimen was evident. Meta-analysis suggested a statistically significant reduction (RR 0.41, CI 0.27-0.63) in asthma exacerbation with vitamin D therapy. LIMITATIONS: Due to variability in outcome selection and missing data, it was not possible to perform meta-analysis for pulmonary function testing and asthma symptom scores. Vitamin D-related adverse events were not considered in four of five papers. CONCLUSIONS: Available evidence from this systematic review suggests that high dose vitamin D may prevent asthma exacerbation. This should be confirmed through larger well-designed randomised controlled trials.
