Vitamin D status is associated with bone mineral density in adolescents: Findings from the Korea National Health and Nutrition Examination Survey

Vitamin D is a factor that regulates calcium and bone metabolism. However, the clinical effect of vitamin D on bone mineral density (BMD) remains controversial. We hypothesized that sufficient vitamin D is required to maintain optimal BMD in adolescents. Based on the Korea National Health and Nutritional Examination Survey, data of 1063 adolescents aged 12 to 18 years were analyzed. The association of vitamin D status and other variables, such as body mass index (BMI), calcium intake, physical activity, lean mass, and fat mass, with BMD Z-scores in the lumbar spine, whole body, total femur, and femur neck were examined. We defined vitamin D deficiency as < 12 ng/mL, vitamin D insufficiency as 12 to 20 ng/mL, and sufficiency as > 20 ng/mL according to the 25-hydroxyvitamin D (25-OHD) level. The mean 25-OHD concentration of subjects was below normal, at 16.28 ng/mL. Subjects with vitamin D deficiency, insufficiency, and sufficiency comprised 20.5%, 58.6%, and 20.9% of all subjects, respectively. The vitamin D sufficient group had higher BMD Z-scores compared to the insufficient group, and the insufficient group had higher BMD Z-scores compared to the deficient group. In linear regression analysis, 25-OHD level, BMI, calcium intake, physical activity, lean mass, and fat mass were positively associated with BMD Z-scores. 25-OHD level was positively associated with BMD Z-scores, even after adjusting for other factors. This study suggests that vitamin D status is positively associated with BMD in adolescents; therefore, maintaining sufficient vitamin D levels during adolescence is crucial to prevent low BMD.