Vitamin D supplementation and the risk of colds in patients with asthma
Reviewed by: Alan Gaby, MD
Author: Denlinger LC, et al
Reference: Vitamin D supplementation and the risk of colds in patients with asthma. Am J Respir Crit Care Med 2016;193:634-641.
Design: Randomized, double-blind, placebo-controlled trial.
Participants: Four hundred eight U.S. adults with mild-to-moderate asthma, a plasma 25-hydroxyvitamin D (25[OH]D) level less than 30 ng/ml, and asthma symptoms despite treatment with an inhaled glucocorticoid. The mean 25(OH)D level at baseline was 15.6 ng/ml in African Americans and 20.4 ng/ml in all others.
Study Medication and Dosage: Vitamin D3 or placebo. The dosage of vitamin D3 was 100,000 IU as a bolus, followed by 4,000 IU per day for 28 weeks, while tapering the inhaled glucocorticoid.
Primary Outcome Measure: The incidence of colds.
Key Findings: The incidence of colds was nonsignificantly higher in the vitamin D group than in the placebo group (1.48 vs. 1.24 colds per person per year; p = 0.15). Among African Americans, the incidence of colds was significantly higher by 70% in the vitamin D group than in the placebo group (p = 0.02). The mean plasma 25(OH)D level increased to 41.9 ng/ml during the study.
Practice Implications: These findings indicate that supplementation with relatively large doses of vitamin D did not prevent colds in patients with poorly controlled asthma. To the contrary, colds tended to occur more frequently in patients receiving vitamin D than those receiving placebo. Among African Americans, this increase in frequency of colds was statistically significant. Previous research has shown that vitamin D metabolism and vitamin D requirements may differ between blacks and whites. In addition, a 25(OH)D concentration that indicates vitamin D deficiency in whites may indicate normal vitamin D status in blacks. The results of the present study support previous research suggesting that aggressive vitamin D supplementation may do more harm than good in African Americans.