Serum 25-hydroxyvitamin D levels in relation to lung function and exhaled nitric oxide in children.

OBJECTIVE: To investigate the relationship of vitamin D status with lung function and fraction of exhaled nitric oxide (FeNO) in a population sample of children. STUDY DESIGN: A total of 1315 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 forced vital capacity was 53.4 mL (SE, 26.5 mL; P = .045), and the mean forced expiratory volume in 1 second was 48.2 mL (SE, 23.6 mL; P = .042) 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 81.9 mL (SE, 26.7 mL; P = .002) for forced vital capacity and 55.2 mL (SE, 23.7 mL; P = .020) for forced expiratory volume in 1 second. There was no significant association between serum 25(OH)D levels and FeNO after adjusting for confounders. CONCLUSIONS: Our results demonstrate 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.

Suboptimal vitamin D status in a population-based study of Asian children: prevalence and relation to allergic diseases and atopy.

BACKGROUND: New evidence shows high prevalence of vitamin D deficiency in many countries and some studies suggest a possible link between vitamin D status and allergic diseases. The objectives of this study were to determine the prevalence of suboptimal vitamin D status in a population sample of Asian children and to investigate the relationship of vitamin D status with allergic diseases and atopy. METHODS: Children aged 5-18 years (N = 1315) in the Prediction of Allergies in Taiwanese CHildren (PATCH) study were evaluated using questionnaires, anthropometric measurements, and serum levels of 25-hydroxyvitamin D [25(OH)D] and total and specific immunoglobulin E (IgE). RESULTS: The mean concentration of serum 25(OH)D was 20.4 ng/mL (SD: 7.1 ng/mL). Vitamin D deficiency (defined as serum 25(OH)D<20 ng/mL) was present in 670 subjects (51.0%), while vitamin D insufficiency (defined as serum 25(OH)D<30 ng/mL) was observed in 1187 subjects (90.3%). Older age (P<0.001), female gender (P<0.001), higher body mass index (P = 0.001), winter and spring seasons (compared to summer; P both<0.001), and passive smoking (P = 0.011) were independently associated with low serum 25(OH)D levels. After adjusting for potential confounders, serum 25(OH)D status had no association with asthma, rhinitis, eczema, atopy, or total serum IgE (all P>0.05). CONCLUSIONS: Low serum 25(OH)D levels are remarkably common in this population sample of Asian children, suggesting that millions of children living in Taiwan may have suboptimal levels of vitamin D, which should be a matter of public health concern. Our results provides epidemiological evidence against the association of vitamin D status with various allergic diseases and atopy in Asian children.