Risk factors for low vitamin D status in Korean adolescents: the Korea National Health and Nutrition Examination Survey (KNHANES) 2008-2009

Objective: To evaluate the prevalence of vitamin D deficiency and predictors for low vitamin D status in Korean adolescents living between latitudes 338 and 39 degrees 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 (logtransformed 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 (P50.012) 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.