Longitudinal associations between vitamin D status and biomarkers of inflammation in a pan-European cohort of children and adolescents.

Purpose: To investigate longitudinal associations between the vitamin D status and inflammatory markers in children and adolescents.

Methods: Children from eight European countries from the IDEFICS/I.Family cohort with repeated measurements were included in this study. A linear mixed-effect model was used to model the association of serum 25(OH)D as independent variable and z-scores of inflammatory markers [CRP, cytokines, adipokines, combined inflammation score] as dependent variables, where one level accounts for differences between individuals and the other for changes over age within individuals.

Results: A total of 1,582 children were included in the study. In the adjusted model, 25(OH)D levels were positively associated with adiponectin (β = 0.11 [95% CI 0.07; 0.16]) and negatively with the inflammation score (β = - 0.24 [95% CI - 0.40; - 0.08]) indicating that the adiponectin z-score increased by 0.11 units and the inflammation score decreased by 0.24 units per 12.5 nmol/l increase in 25(OH)D. In children with overweight or obesity, only a positive association between 25(OH)D and IP-10 was observed while in children with normal weight adiponectin was positively and the inflammation score was negatively associated. Associations of vitamin D with adiponectin and the inflammation score were stronger in girls than in boys and a positive association with TNF-α was observed only in girls.

Conclusion: Our results suggest that an increase in vitamin D concentrations may help to regulate inflammatory biomarkers. However, it seems to be no benefit of a better vitamin D status in children with overweight/obesity unless their weight is managed to achieve an improved inflammatory marker status.