Objective: To evaluate the prevalence of vitamin D deficiency and predictors for low vitamin D status in Korean adolescents living between latitudes 33° and 39° N.
Design: A descriptive cross-sectional study.
Setting: Korea National Health and Nutrition Examination Survey (KNHANES) 2008-2009.
Subjects: A total of 1510 healthy adolescents aged 12-18 years (806 male, mean age 14.7 years) participated. Possible predictors for low vitamin D status (log-transformed 25-hydroxyvitamin D (25(OH)D) concentrations) were evaluated.
Results: The prevalence of vitamin D deficiency (25(OH)D<20 ng/ml) was 89.1% in spring, 53.7% in summer, 63.9% in autumn and 90.5% in winter. Winter season, older age, higher education level reached, being female, being obese, a lack of vitamin D supplementation, lower milk consumption (0-<200 ml/d) and a lack of physical activity were unadjusted predictors (all P < 0.05). Multiple linear regression analysis showed that winter season (P < 0.001), higher education level (P < 0.001) and a lack of vitamin D supplementation (P = 0.012) were independent predictors for low vitamin D status. The modifying effect of season on the association between vitamin D supplement use and vitamin D status was significant (P < 0.001).
Conclusions: Vitamin D deficiency was highly prevalent in Korean adolescents, especially those in higher school grades. Vitamin D supplementation may contribute to maintain a better vitamin D status with lower seasonal variation. Further studies are required to determine optimal vitamin D intakes to maintain sufficient vitamin D status for Korean adolescents.