Predictors of differences in vitamin D levels in children and adolescents and their relation to endurance performance.

AIMS The present study investigated whether sociodemographic factors and physical activity (PA) are associated with differences in serum 25-hydroxyvitamin D [25(OH)D] levels and whether these differences are associated with varying levels of endurance performance and body mass index (BMI) in children and adolescents. SUBJECTS AND METHODS Path analyses were based on data of a nationwide, cross-sectional German Health Interview and Examination Survey for Children (KiGGS; 2003 until 2006) for 25(OH)D and the embedded 'motor function module' for PA and endurance performance. The data were collected from 3,437 children and adolescents aged 6-17 years clustered in three age groups: 6-10, 11-13 and 14-17 years. RESULTS PA is affected by socioeconomic status and (non-)immigration background, 25(OH)D is only affected by (non-)immigration background and only in childhood. PA and 25(OH)D were not associated in those aged 11-13 years. In adolescence, lower 25(OH)D levels are associated with lower endurance performance and a higher BMI. CONCLUSIONS Our results did not reveal a universally significant effect of sociodemographic factors on 25(OH)D. The association between 25(OH)D and endurance performance might reflect the effects of 25(OH)D on muscle function. Predictors of 25(OH)D status other than sunlight exposure and its health effects in the pediatric age group should be explored further.