Efficacy of vitamin D supplementation on COPD and asthma control: A systematic review and meta-analysis

Systematic review and meta-analysis of randomized controlled trials in participants with COPD or asthma. The evidence base included 11 COPD RCTs with 1183 patients and 19 asthma RCTs with 2025 patients; several asthma studies were conducted in children.

Vitamin D supplementation was evaluated across randomized trials in COPD and asthma, using a wide range of regimens including daily, weekly, monthly, single-dose, and loading-plus-maintenance approaches. Doses ranged from 100 IU daily to 400,000 IU as a single dose, with durations from 10 days to 48 weeks; several studies used vitamin D3.

Vitamin D supplementation showed some beneficial effects on respiratory outcomes, but the overall response was heterogeneous. Pooled findings favored improvements in pulmonary function, including FEV1% and, in asthma, FEV1/FVC, and in COPD quality of life measured by SGRQ also improved. Vitamin D was associated with reduced inflammatory markers such as IL-5 and IgE, and IL-10 increased in participants with vitamin D deficiency. Exacerbations and mortality were not consistently affected, and the authors caution that effects may be overestimated despite the low-cost, low-risk profile of supplementation.

The included trials were heterogeneous in population, condition, dose, and treatment duration, which limits certainty about the size and consistency of benefit. Exacerbation and mortality outcomes were not consistently improved, and the authors note a possibility of overestimation. Generalizability is also limited by the mix of adult and pediatric asthma studies and the absence of consistently extractable arm-level outcome data in the supplied packet.