A study gave a single huge dose of vitamin D (250,000 IU) to adults with cystic fibrosis during a lung flare‑up and found it cut two inflammation markers (TNF‑α and possibly IL‑6) after 12 weeks, but it didn’t change the antimicrobial peptide LL‑37 or other cytokines. The results are specific to sick CF patients and don’t directly tell us how to use vitamin D for general health or performance.

Patients with cystic fibrosis (CF) suffer from chronic lung infection and inflammation leading to respiratory failure. Vitamin D deficiency is common in patients with CF, and correction of vitamin D deficiency may improve innate immunity and reduce inflammation in patients with CF. We conducted a double-blinded, placebo-controlled, randomized clinical trial of high-dose vitamin D to assess the impact of vitamin D therapy on antimicrobial peptide concentrations and markers of inflammation. We randomized 30 adults with CF hospitalized with a pulmonary exacerbation to 250,000 IU of cholecalciferol or placebo, and evaluated changes in plasma concentrations of inflammatory markers and the antimicrobial peptide LL-37 at baseline and 12 weeks post intervention. In the vitamin D group, there was a 50.4% reduction in tumor necrosis factor-α (TNF-α) at 12 weeks (P<0.01), and there was a trend for a 64.5% reduction in interleukin-6 (IL-6) (P=0.09). There were no significant changes in IL-1β, IL-8, IL-10, IL-18BP and NGAL (neutrophil gelatinase-associated lipocalin). We conclude that a large bolus dose of vitamin D is associated with reductions in two inflammatory cytokines, IL-6 and TNF-α. This study supports the concept that vitamin D may help regulate inflammation in CF, and that further research is needed to elucidate the potential mechanisms involved and the impact on clinical outcomes.