Vitamin D has important functions in the immune system. In recent years, several studies have reported an association between vitamin D levels, atopy, asthma and respiratory tract infections.
Objective
We aimed to investigate whether vitamin D insufficiency in asthmatic adults associates with atopy, poor asthma control, and more frequent respiratory tract infections, and whether these patients can benefit from vitamin D supplementation.
Methods
The study included 62 adult patients diagnosed with asthma. At the first visit, patients underwent pulmonary function testing, skin prick testing with panel of aeroallergens, and 25-Hydroxyvitamin D levels were measured. Asthma Control Test (ACT) questionnaires were administered and records were obtained regarding number of visits to a medical centre for respiratory tract infections for the previous year. Subsequently, patients with vitamin D deficiency received 2000 I.U. vitamin D3 daily for 6 months (from October to March). At the end of that period, all patients were reassessed.
Results
Seventeen patients (27%) were found to have vitamin D levels lower than 30 ng/ml, considered to be insufficient. These patients had poorer asthma control as indicated by ACT scores, and had a significantly higher rate of allergic sensitization, compared to the vitamin D sufficient asthmatics. Patients with vitamin D insufficiency had an average number of medical visits for respiratory infections the previous year of 3.94, while after vitamin D supplementation the average was 2.17. ACT scores increased significantly at the end of the 6 month period, while spirometric values did not change significantly.
Conclusions
We found that vitamin D insufficiency in patients with asthma correlates with allergic sensitization. Vitamin D supplementation in these patients resulted in better asthma control, possibly due to fewer episodes or respiratory tract infections.