Effect of vitamin D supplementation on cystic fibrosis pulmonary exacerbations: A pilot randomized crossover clinical trial

Control of pulmonary exacerbations (PEs) is highly important in the treatment of cystic fibrosis (CF). Given the evidence of the extra skeletal properties of vitamin D, this study aimed to evaluate the effect of supplementation with an extra dose of vitamin D on CF PEs. This is a randomized crossover clinical trial conducted in Brazil. Subjects were randomly allocated to receive vitamin D (5,000-10,000 IU/day, liquid, or gelatin capsules) followed by standard treatment (400-2,000 IU/day of vitamin D), or standard treatment followed by vitamin D for three months, with 9-month washout separating each treatment period. The primary endpoint was the number of PEs during the intervention period. In addition, a 6-month period following the use of the extra dose and the regular dose were assessed. Secondary outcome included change in serum 25(OH)D after the end of supplementation. 34 subjects completed the study (16 received vitamin D first, and 18 received standard treatment first; median age: 5.16 years (1.74:8.07)). A significant statistical reduction in pulmonary exacerbations with the use of the extra dose of vitamin D was not detected (P = 0.10). No effect of vitamin D on PEs was observed after the end of supplementation. More than half of the subjects had suboptimal levels of 25(OH)D pre-supplementation and only 58% achieved desirable levels of the vitamin. Our findings reinforce the high prevalence of hypovitaminosis D in subjects with CF, despite routine supplementation. Further robust evidence is needed to analyze the possible effect of vitamin D in reducing CF pulmonary exacerbations.