Vitamin D Supplementation Doesn't Prevent Colds in Adult Asthma Patients

Vitamin D deficiency has been linked to asthma and to susceptibility for acute respiratory tract infections, but vitamin D supplementation has yielded inconsistent benefit. In a previously published trial, 408 adult patients with mild-to-moderate asthma and serum 25-hydroxyvitamin D (25[OH]D) levels <30 ng/mL received placebo or cholecalciferol (vitamin D₃; 100,000 IU initial dose, then 4000 IU daily) for 28 weeks while inhaled corticosteroids were tapered. Time to first asthma treatment failure and incidence of exacerbations were similar in the two groups (NEJM JW Gen Med Jul 1 2014 and JAMA 2014; 311:2083). Now, in a prospectively planned, secondary analysis, the investigators evaluated whether vitamin D₃ supplementation lowers the incide…