Effect of vitamin D on lung function assessed by forced oscillation technique in asthmatic children with vitamin D deficiency: A randomized double-blind placebo-controlled trial.

Background: The role of vitamin D and asthma in pulmonary function changes showed conflicting result.

Objective: To evaluate if vitamin D treatment would improve lung function assessed by forced oscillation technique (FOT) in vitamin D deficient asthmatic children.

Methods: A randomized double-blind placebo-controlled trial was performed in children, aged 3-18 years with well controlled asthma. Serum total 25(OH)D and FOT parameters including respiratory resistance at 5 Hz (R5), at 20 Hz (R20), respiratory reactance at 5 Hz (X5) and area of reactance (ALX), resonance frequency (Fres) were evaluated at baseline, 1 month and 3 months. Vitamin D deficient patients (serum total 25(OH)D < 20 ng/ml) were randomized to receive treatment with vitamin D2 (tVDD) or placebo (pVDD). Non-vitamin D deficient patients (nVDD) received placebo as a control group.

Results: A total of 84 children were recruited, 43 patients in nVDD group, 20 in tVDD group and 21 in pVDD group. There were no significant differences in age, sex, height and weight among groups. There were no significant differences of FOT parameters among groups at all visits. There was a trend toward decrease in R5/R20 from baseline to 1 month and 3 months visit in all groups, but the statistically significant improvement was observed only in nVDD group. Serum 25(OH)D showed no correlation with % predicted of FOT measures.

Conclusions: Vitamin D treatment in asthmatic children who had vitamin D deficiency may have no short term beneficial effect on pulmonary function assessed by FOT. Vitamin D supplementation in all asthmatic patient needs further study.