Extra-skeletal impact of vitamin D supplementation protocol in an adult population with cystic fibrosis.

BACKGROUND: Due to lack of vitamin D absorption in patients with cystic fibrosis (CF), vitamin D supplementation becomes necessary. Our aim was to study the association between serum vitamin D levels and key clinical factors, such as nutritional status, pulmonary function and pulmonary exacerbations (PEx) frequency, in an adult CF population. METHODS: Prospective analysis of a published vitamin D (VitD3) supplementation protocol (N = 200 adult patients) over a follow-up period of 5 years. Data were collected from the medical files before (baseline) and after (follow-up) the implementation of the VitD3 supplementation protocol, between 2009 and 2014. Serum samples to measure vitamin D were also collected at baseline and follow-up. RESULTS: A positive relationship between serum vitamin D and lung function was observed at baseline (R = 0.158, P = 0.027), but it disappeared at follow-up (P = 0.454). There was no association between serum vitamin D levels and body mass index. At follow-up, patients with significantly higher serum vitamin D levels were women, older in age, had CF-related diabetes or had a history of recurring PEx. CONCLUSION: No direct link was observed between heightened serum vitamin D and lung function or BMI in an adult CF population. We suggest that better compliance to treatments and closer follow-up from health professionals could partially explain why such patients reached higher vitamin D serum levels.