Relationship of vitamin D status to adult lung function and COPD

BACKGROUND: There is considerable interest in the possible role of vitamin D in respiratory disease, but only one population-based study has reported associations with lung function. METHODS: The cross-sectional relationships of total dietary vitamin D intake, serum 25 hydroxy vitamin D (25(OH)D) concentrations and three vitamin D receptor (VDR) polymorphisms (Apa1, Fok1 and Cdx2) with lung function and spirometrically-defined chronic obstructive pulmonary disease (COPD) were investigated in men and women aged 59-73 years in the Hertfordshire Cohort Study, UK. RESULTS: After controlling for confounders, total vitamin D intake was positively associated with forced expiratory volume in 1 s (FEV(1); difference in FEV(1) between top and bottom quintiles of intake 0.079 l (95% CI 0.02 to 0.14), p trend=0.007, n=2942), ratio of FEV(1) to forced vital capacity (FEV(1)/FVC; p trend=0.008) and negatively associated with COPD (OR comparing top and bottom quintiles 0.57 (95% CI 0.38 to 0.87), p trend=0.02). In contrast, serum 25(OH)D concentrations were not related to FEV(1) (p trend=0.89, n=1197) but were positively associated with COPD (p trend=0.046). VDR genotypes were unrelated to lung function and did not modify the effects of dietary intake or 25(OH)D concentrations on lung function. CONCLUSIONS: The results of this study did not confirm a positive association between blood 25(OH)D concentrations and adult lung function. The apparent relationships with dietary vitamin D are likely to be explained by other highly correlated nutrients in the diet.