Improved control of childhood asthma with low‐dose, short‐term vitamin D supplementation: a randomized, double‐blind, placebo‐controlled trial

Abstract Background In our prior randomized trial on preventing influenza, asthma attacks as a secondary outcome occurred less often in the vitamin D group than in the placebo group. We aimed to clarify whether low‐dose, short‐term vitamin D supplementation, in addition to standard treatments, improves control of childhood asthma. Methods We conducted a randomized, double‐blind, placebo‐controlled trial comparing vitamin D3 supplements (800 IU /day) with placebo for 2 months in schoolchildren with asthma. The primary outcomes were frequency and severity of asthma judging from changes in asthma control levels defined by the Global Initiative for Asthma ( GINA ) by collaborating doctors at 2 and 6 months. Results Japanese schoolchildren with asthma ( n = 89) were randomly assigned to receive vitamin D ( n = 54) or placebo ( n = 35). At 2 months, GINA asthma control was significantly more improved in the vitamin D group compared with the placebo group ( P = 0.015). Childhood asthma control test ( CACT ) scores, a secondary outcome, were also significantly ( P = 0.004) improved in the vitamin D group compared with the placebo group at 2 months, and differences remained significant ( P = 0.012) at 6 months. The proportion of patients with a peak expiratory flow rate <80% predicted was significantly less in the vitamin D group (8/54: 15%) than in the placebo group (12/35: 34%) at 6 months ( P = 0.032). Conclusions Low‐dose, short‐term vitamin D supplementation in addition to standard treatment may improve levels of asthma control in schoolchildren.