Vitamin D for the management of asthma.
Level 1 - systematic review of randomized trials
Systematic review and meta-analysis of randomized controlled trials
PubMed 36744416 · doi:10.1002/14651858.CD011511.pub3
What was done
This Cochrane systematic review and meta-analysis updated evidence through September 2022 on the efficacy and safety of vitamin D (or its hydroxylated metabolites) for asthma. Authors included double-blind, randomized, placebo-controlled trials in children and adults. The primary outcome was the incidence of severe asthma exacerbations requiring systemic corticosteroids. Secondary outcomes included exacerbation rates, time to first exacerbation, hospital/emergency department visits, symptom control scores (ACT/cACT), lung function (FEV1), and serious adverse events.
What was found
Twenty trials were included (15 in 1,155 children, 5 in 1,070 adults; trial durations 3 to 40 months; mostly cholecalciferol). Vitamin D supplementation did not reduce the proportion of patients experiencing ≥1 severe exacerbation requiring systemic corticosteroids (OR 1.04, 95% CI 0.81 to 1.34; I² = 0%; 14 studies, 1,778 participants; high-quality evidence; absolute risk 226 per 1,000 in vitamin D vs. 219 per 1,000 in placebo). Supplementation also did not significantly reduce the rate of severe exacerbations (rate ratio 0.86, 95% CI 0.62 to 1.19; I² = 60%; 10 studies, 1,599 participants) or time to first exacerbation (HR 0.82, 95% CI 0.59 to 1.15; 3 studies, 850 participants). Subgroup analyses showed no modification by age, baseline vitamin D status, dose, or regimen. There was no difference in serious adverse events (OR 0.89, 95% CI 0.56 to 1.41; 12 studies, 1,556 participants).
Why it matters
Overturning earlier suggestive findings, this updated review provides high-quality evidence that routine vitamin D supplementation does not prevent severe exacerbations or improve symptoms in children and adults with asthma.
Limits
The vast majority of participants had mild-to-moderate asthma, leaving patients with severe asthma poorly represented. Profound baseline vitamin D deficiency (<25 nmol/L) was rare across included cohorts, limiting conclusions for severely deficient individuals. Almost all trials tested cholecalciferol (vitamin D3); only one small trial evaluated calcidiol.
Cited by
- contradicts Having sufficient vitamin D has been shown to improve asthma.