Background and aims There is increasing evidence that vitamin D plays a role in lung diseases, but it is not clear whether vitamin D is related to lung function and airway inflammation. The objective of this study was to investigate the relationship of vitamin D status with lung function and fraction of exhaled nitric oxide (FeNO) in a population sample of children.

Methods 1,315 children aged 5–18 years were evaluated using serum 25-hydroxyvitamin D [25(OH)D] levels, spirometry, a single-breath online FeNO measurement, and questionnaires.

Results After adjusting for confounders, the mean FVC was 53.7 mL (SE, 26.6 mL; p = 0.043) and the mean FEV₁ was 48.6 mL (SE, 23.6 mL; p = 0.040) lower for children with insufficient serum 25(OH)D levels (20–29.9 ng/mL) compared with those with sufficient 25(OH)D levels (≥30 ng/mL). The mean difference between children with deficient (<20 ng/mL) and sufficient levels of serum 25(OH)D was 83.6 mL (SE, 26.7 mL; p = 0.002) for FVC and 56.9 mL (SE, 23.8 mL; p = 0.017) for FEV₁. There was no significant association between serum 25 (OH)D levels and FeNO after adjusting for confounders.

Conclusions Our results demonstrate new evidence for a significant relationship between insufficient serum vitamin D levels and worse lung function in children in the community with a suggested dose-response effect. Our findings also suggest that vitamin D status is not a significant determinant of FeNO in children in the general population.