Inverse relation between vitamin D and serum total IgG in the Scandinavian Cystic Fibrosis Nutritional Study

Overview & Synopsis

Background/Objectives: The hallmark of cystic fibrosis (CF) is chronic lung inflammation. The severity of lung disease is closely correlated with IgG levels. Beyond its contribution to the bone health, the importance of vitamin D has not been fully recognized due to lack of human studies providing evidence of its benefit. In context of the recently described immunomodulatory functions of vitamin D, we aimed to assess the relationship between vitamin D and IgG levels. Subjects/Methods: 896 CF patients were included (0.53 - 65.9 years) from 7 centers in Denmark, Norway and Sweden. Serum 25-hydroxyvitamin D (25OHD) and total IgG were measured, spirometry was carried out and vitamin D intake data were gathered using a seven-day dietary food record. Multiple linear regression analyses were performed for IgG and FEV1 as dependent variables, and serum 25OHD, daily food and supplemented vitamin D sources of intake as independent variables. The model was controlled for age, gender, genotype, CF-related diabetes, season, infection/colonization status, long-term oral corticosteroid treatment, long-term treatment with macrolide antibiotics, pancreatic insufficient phenotype and Body Mass Index z-score. Results: Serum total IgG levels were negatively associated with serum 25OHD (adjusted R2=0.376; beta=-0.02; p