Association Between Serum Vitamin D and Metabolic Risk Factors in Korean Schoolgirls

Objectives

Vitamin D, a key regulator of bone metabolism, has been recently been linked with energy homeostasis and metabolic disorders in western countries. However, few studies have focused on the association of vitamin D with metabolic risk factors among Asian children. We studied the prevalence of vitamin D insufficiency and the association of 25-hydroxyvitamin D [25(OH)D] with metabolic risk factors in Korean schoolgirls.

Methods

The sample consisted of 320 13-year-old girls recruited from two middle schools in the city of Gwacheon, Korea (latitude 37°N), in July 2011. Anthropometric and blood biochemistry data were obtained for this cross-sectional observational study. We also obtained lifestyle data from questionnaires and dietary data from 3-day food diaries.

Results

Vitamin D deficiency [25(OH)D < 20 ng/mL] was noted in 63.8% of participants. The mean 25(OH)D level was not significantly lower in the overweight group. Level of physical activity and vitamin D intake did not significantly affect 25(OH)D. However, 25(OH)D levels were positively correlated with milk intake and negatively correlated with soft drink intake. Serum 25(OH)D had a negative relationship with fasting glucose and insulin resistance index (homeostasis model assessment-insulin resistance; HOMA-IR) after adjustment for physical activity and body mass index z score (r = −0.144, p = 0.015), and with metabolic risk score similarly (r = −0.141, p = 0.012). Levels of insulin, HOMA-IR, and systolic blood pressure were higher in girls with deficient 25(OH)D levels than in those with sufficient levels.

Conclusion

We found that low 25(OH)D levels were associated with higher blood glucose and insulin resistance. Korean girls with low 25(OH)D levels could be at increased risk for metabolic disorders.