ReviewTreatment of vitamin D deficiency in cystic fibrosis

•Vitamin D insufficiency is common in patients with cystic fibrosis.•Vitamin D status is important for bone health, lung and immune function in patients with cystic fibrosis.•Treatment of vitamin D insufficiency in patients with cystic fibrosis requires high dose cholecalciferol or ergocalciferol.•Randomized, double blind, placebo controlled, large scale clinical trials are underway to evaluate the role of vitamin D as an adjunctive treatment in patients with cystic fibrosis.

Vitamin D deficiency occurs frequently in patients with cystic fibrosis (CF). Vitamin D is important for optimal mineralization of bone and may be important for other comorbidities commonly occurring in patients with CF. Vitamin D deficiency in patients with CF can arise from various causes including pancreatic exocrine insufficiency, lack of outdoor activity, and alterations of vitamin D metabolism. Due to fat malabsorption stemming from pancreatic insufficiency, higher oral doses of vitamin D are necessary to correct and maintain optimal vitamin D status in patients with CF. Recent studies have demonstrated that higher vitamin D status is associated with better lung function and that vitamin D therapy may help recovery from pulmonary exacerbations of CF. The mechanisms by which vitamin D may exert its beneficial actions in CF are unclear but likely related to the role vitamin D has in modulating the adaptive and innate immune response. Large randomized clinical studies to evaluate the potential role of vitamin D as adjunctive therapy in CF that goes beyond bone are necessary.