Associations Between Serum 25-Hydroxyvitamin D Levels and Metabolic Syndrome Among Korean Adolescents: Based on the Korea National Health and Nutrition Examination Survey in 2022–2023

Background/Objectives: Vitamin D is a nutrient involved not only in bone metabolism but also in metabolic functions, and deficiency is common during adolescence. This study aimed to describe the distribution of serum 25-hydroxyvitamin D levels among Korean adolescents and to examine their associations with metabolic syndrome and its individual components. Methods: We analyzed data from the 2022–2023 Korea National Health and Nutrition Examination Survey. Adolescents aged 10–18 years with serum 25-hydroxyvitamin D measurements were included (unweighted N = 880). Weighted analyses were performed by categorizing serum 25-hydroxyvitamin D levels into quartiles. Associations between vitamin D quartiles and anthropometric and metabolic parameters were examined using complex-sample general linear models, and odds ratios for metabolic syndrome and its individual components according to vitamin D deficiency were estimated using complex-sample logistic regression models. Results: Weighted prevalence of vitamin D deficiency ( 0.5 (OR 2.63), and BMI ≥ 95th percentile (OR 1.89), while metabolic syndrome was not significant. Conclusions: Vitamin D appears to play an important role in metabolic health in adolescents and was particularly associated with general and central obesity.