Vitamin D Supplementation in Childhood Asthma: A Systematic Review and Meta-analysis of Randomised Controlled Trials
BackgroundThere is conflicting evidence for vitamin D supplementation in childhood asthma. We aimed to systematically synthesize the evidence on the efficacy and safety of vitamin D supplementation in childhood asthma.MethodsWe searched electronic databases (Medline, Embase, Web of Science) and register (CENTRAL) for randomised controlled trials (RCTs) published until September 30, 2021. RCTs enrolling asthmatic children (1–18 years) and comparing vitamin D against placebo/routine care were included if they met at least one of the endpoints of interest (asthma attacks, emergency visits, hospitalisation). We used the Risk of Bias (RoB) 2 tool for risk of bias assessment. Random-effects meta-analysis with RevMan 5.3 software was done. The GRADE approach was used to assess the level of certainty of the evidence.ResultsEighteen RCTs (n=1579 participants) were included. The pooled meta-analysis did not find a significant effect of vitamin D supplementation on asthma attacks requiring rescue systemic corticosteroids (6 studies, 445 participants, Risk ratio: 1.13; 95% CI: 0.86 to 1.48, I2–0%) (Moderate-certainty evidence). In addition, there was no significant difference in the proportion of children with asthma attacks of any severity (11 trials, 1132 participants, RR: 0.84; 95% CI: 0.65 to 1.09; I2–58%) (Very-low certainty evidence). Vitamin D does not reduce the need for emergency visits (3 studies, 361 participants, RR: 0.97; 95% CI: 0.89 to 1.07, I2–0%) and hospitalisation (RR: 1.38; 95% CI: 0.52 to 3.66, I2–0%) (Low certainty evidence).ConclusionVery low to moderate certainty evidence suggests that vitamin D supplementation might not have any protective effect in childhood asthma.