OBJECTIVE

To assess Vitamin D status in children aged 0-6 years in Quanzhou, China, and compare the impact of diagnostic criteria on deficiency/sufficiency classification.

METHODS

This cross-sectional study enrolled 1,183 healthy children aged 0-6 years (January 2022-March 2023). Serum 25(OH)D levels were measured via ELISA, and anthropometric data were collected. Participants were stratified by sex, season, age, WLZ, BMI, and Vitamin A status to analyze Vitamin D variations. Diagnostic criteria impacts on classification were evaluated.

RESULTS

Mean serum 25(OH)D was 73.02 nmol/L (: 58.48-89.09), with no sex-based differences ( > 0.05). Levels varied by season (highest in summer: 75.85 nmol/L; lowest in winter: 69.00), and age (infants > toddlers > preschoolers), all  < 0.05. Serum 25(OH)D were observed to decrease with increasing WLZ (Weight-for-Length Z-score) and BMI, though no statistically significant differences were found for either parameter (both  > 0.05) Using Criterion I, 2.46% were deficient, 9.97% insufficient, and 87.57% sufficient (  = 1589.053,  < 0.001). With Criterion II, rates shifted to 12.43, 40.74, and 46.83%, respectively (  = 239.271,  < 0.001). Classification discrepancies were significant across subgroups (sex, season, age, BMI; all <0.05), with poor inter-criteria agreement ( = 0.071,  < 0.001). Age, season, BMI, and Vitamin A independently predicted sufficiency ( < 0.05).

CONCLUSION

This study underscores two critical implications: (1) Vitamin D deficiency/sufficiency classifications are critically dependent on diagnostic criteria, necessitating region-specific guidelines and standardized threshold selection in practice and research. (2) Given the influence of latitude on Vitamin D synthesis, targeted interventions-particularly increased winter dosing for young children-should be tailored to age and seasonal variations.