Aim: To investigate vitamin D status and its determinants in school-aged children living in Auckland, New Zealand.
Methods: Healthy children (n=507) aged 8-11 years were recruited from six primary schools to include a range of ethnicities and sociodemographic characteristics. Finger-prick blood spots were collected and analysed for capillary 25-hydroxyvitamin D (25(OH)D). Weight and percentage of body fat (%BF) were measured using the InBody 230 (Biospace Co. Ltd., Seoul, Korea). Information related to ethnicity, skin colour, physical activity and sun exposure were sought from parents through a questionnaire.
Results: Mean±standard deviation (SD) 25(OH)D concentration were 64±21 nmol/L, with 31% of the population presenting with 25(OH)D≥75nmol/L, 41% 50-75nmol/L and 28%<50nmol/L. Capillary 25(OH)D was significantly higher in New Zealand European compared to all other ethnic groups (75±20nmol/L, P<0.001). As expected, children with dark/brown skin colour had lower 25(OH)D levels compared to other skin colour categories (51±18nmol/L, P<0.001). Using multiple logistic regression analysis, determinants of 25(OH)D were %BF and ethnicity.
Conclusion: Approximately one-third of this population had 25(OH)D<50nmol/L. Determinants of a 25(OH)D<50nmol/L included %BF and ethnicity. Wintertime serum 25(OH)D was highly variable. There are some children at high risk of 25(OH)D<50nmol/L for whom supplementation may be considered.