In a small randomized clinical trial, researchers at Karolinska Institute in Sweden showed that vitamin D supplements may improve lung function in cystic fibrosis (CF) patients. A daily intake of high levels of vitamin D are required, however, for the effects to be noticed.
Lung function decline is the major cause of morbidity and mortality in cystic fibrosis. This is the result of chronic colonization of the lungs by bacteria and acute airway infections.
It is well established that CF patients suffer from a lack of vitamin D, a condition that is still frequently maintained even when patients take vitamin D supplements. In fact, vitamin D levels have been shown to correlate with lung function, the annual number of pulmonary exacerbations, and the immune status of CF patients.
Vitamin D is important for bone health, and the current recommendations for vitamin D supplements in CF were designed according to this specific parameter. However, due to its effects on the immune system, in this study researchers investigated how vitamin D supplements influence immune responses (measured by the level of cytokines, a group of small proteins released by immune cells that act as chemical messengers) and lung function in cystic fibrosis.
The study’s main objective was to establish the most efficient dosing strategy for daily vitamin D supplements.
Researchers investigated the effectiveness of vitamin D supplements — currently sold in two distinct forms, ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3) — at increasing the blood levels of vitamin D (assessed as 25-hydroxyvitamin D, s25OHD).
The team conducted a small clinical trial study (NCT01321905) where 16 cystic fibrosis patients were randomly assigned to receive vitamin D2 or D3. A control group did not receive any extra vitamin D. Patients under 16 years old received a starting dose of 35,000 IU (international units), while those 16 and older received 50,000 IU of vitamin D2 or D3 per week. The weekly dose was given as seven once-daily doses. All patients maintained their ordinary vitamin supplements.
The study was conducted for three months followed by two months without supplements. In the end, an analysis of the effects was performed on the 13 patients who finished the study.
Researchers observed that to increase serum s25OHD levels, the mean daily dose of vitamin D2 and D3 needed an increase of up to 15,650 and 8,184 IU, respectively. Additionally, both groups of patients (D2 and D3) showed decreased levels of immune system interleukin 8 (IL-8, which is a key mediator associated with inflammation) in plasma at the end of the supplement study.
Patients in the vitamin D3 arm improved their forced vital capacity (FVC, a measure of lung function) compared with baseline, whereas the same was not observed in those receiving vitamin D2.
Overall, changes in s25OHD were positively correlated with an improved quality of life respiratory score at the end of the supplement study in CF adults.
“This pilot trial suggests that high doses are needed to improve vitamin D status in CF patients. Vitamin D supplementation may positively affect the immune system in patients with CF, which might eventually lead to better respiratory function,” the authors wrote in their report.
“Larger long-term placebo-controlled studies are needed to test the new hypotheses generated by this pilot trial,” they added.