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.