Table 2. Trials of vitamin D and asthma morbidity.

GINA: Global Initiative for Asthma; RCT: Randomized clinical trial.

Author	Year	Study Design	Study Sample	Outcome Measures	Findings
Urashima [30]	2010	RCT of 217 school children	All school children with subgroup with clinically diagnosed asthma	Asthma exacerbations	Vitamin supplements reduced the risk of severe asthmatic symptoms
Majak [31]	2011	Randomized, double-blind, parallel arm clinical trial 6-month experimental study of vitamin D3 (500 IU/d) as adjuvant therapy to IC among 48 Polish children	Newly diagnosed asthma	Asthma exacerbations	Children receiving vitamin D supplementation had lower incidence of asthma exacerbations as compared to other groups
Yadav [32]	2014	Randomized double blinded placebo controlled trial on 100 children 1 group received vitamin D3, 60,000 IU/month for 6 months versus placebo	Asthmatic children	Asthma exacerbations and number of emergency visits	Vitamin D has a role in bronchial asthma
Tachimoto [47]	2016	Treatment (n = 54): vitamin D3 800 IU/day orally for 2 months. Control (n = 39): daily oral placebo for 2 months	Asthmatic children (6 to 15 years)	Changes in asthma control levels defined by GINA. Changes in asthma control levels judged by the childhood ACT	Asthma control was significantly improved in vitamin D group versus placebo group (p = 0.015). Childhood asthma control test (CACT) scores were also significantly improved in vitamin D group
Jensen [48]	2016	Active intervention (n = 11): 100,000 IU vitamin D3 oral bolus at baseline, followed by 400 IU vitamin D3 IU orally daily. Control intervention (n = 11): oral placebo at baseline, followed by 400 vitamin D3 IU orally daily	Asthmatic preschool children (1 to 5 years)	Mean group change in total serum 25(OH)D from baseline to 3 months	Group difference in serum 25OHD (7.2 nmol/L; 95% CI: (13.7-28.1) was not significant; 100% vs 54.5% (intervention versus control) had serum 25OHD ≥75 nmol/L
Denlinger [49]	2015	Cholecalciferol (100,000 IU load plus 4,000 IU/d) for 28 weeks or placebo	Adults with asthma	Cold symptom severity, which was assessed using daily scores on the 21-item Wisconsin Upper Respiratory Symptom Survey	Vitamin D supplementation had no effect on the average peak scores (62.0 [95% CI: 55.1–68.9; placebo] and 58.7 [95% CI: 52.4–65.0; vitamin D]; p = 0.39)
Martineau [50]	2015	Six 2-monthly oral doses of 3 mg vitamin D3 (n = 125) or placebo (n = 125) over 1 year	Adults with asthma	Asthma exacerbations and URI	No significant association to first severe exacerbation (HR: 1.02, 95% CI: 0.69-1.53, p = 0.91) or first URI (HR: 0.87, 95% CI: 0.64-1.16, p = 0.34)