Vitamin D status in preschool children and its relations to vitamin D sources and body mass index-Fish Intervention Studies-KIDS (FINS-KIDS).

Objectives: The aims of this study were to determine vitamin D status (serum 25-hydroxyvitamin D [s-25(OH)D]) and examine possible associations between vitamin D status and vitamin D-rich dietary sources, sun exposure, and body mass index in preschool children ages 4 to 6 y.

Methods: This is a cross-sectional study based on baseline data (collected in January-February 2015) from the two-armed randomized controlled trial Fish Intervention Studies-KIDS (FINS-KIDS) conducted in Bergen, Norway. S-25(OH)D concentration was determined by liquid chromatography-tandem mass spectrometry. Information regarding habitual dietary intake, recent sun vacations, and body mass index were assessed with questionnaires answered by the children's caregivers.

Results: The children (n = 212) had a mean (standard deviation) s-25(OH)D of 60.7 (13.8) nmol/L; 18.9% had s-25(OH)D ≤50 nmol/L. In logistic regression models, non-overweight versus overweight status was inversely associated with s-25(OH)D ≤50 nmol/L (odds ratio: 0.41; 95% confidence interval, 0.18-0.95; P = 0.037). Non-sun versus sun vacations were associated with s-25(OH)D ≤75 nmol/L (odds ratio: 5.33; 95% confidence interval, 1.93-14.77; P = 0.001).

Conclusions: The majority of the preschool children (81%) had s-25(OH)D >50 nmol/L. Children with overweight status had an increased risk of s-25(OH)D ≤50 nmol/L, and children who had not been on sun vacations were at a greater risk of s-25(OH)D ≤75 nmol/L.