Association Between Vitamin D Status and Insulin Resistance in Adolescents: A Cross-sectional Observational Study

ObjectiveTo investigate the correlation between vitamin D nutritional status and insulin resistance in pubertal adolescents.MethodsThis cross-sectional observational study employed convenience sampling to recruit 2021-grade(8th grade) students from Jining No.7 Middle School in Shandong Province on June 5, 2023. Data collection included questionnaires, physical examinations, and imaging assessments to obtain general information, secondary sexual characteristics development, and bone age. Venous blood samples were collected to measure fasting blood glucose(FBG), fasting insulin(FINS), homeostasis model assessment of insulin resistance(HOMA-IR), and 25-hydroxyvitamin D[25(OH)D] levels. Spearman correlation analysis and multivariate linear regression models were used to examine the associations between serum vitamin D levels and FBG, FINS, and HOMA-IR.ResultsThe study included 168 pubertal adolescents[69 females(41.1%), 99 males(58.9%); mean age(13.27±0.46) years]. All participants had entered puberty based on sexual development assessment. Vitamin D deficiency was observed in 41 participants(24.4%), insufficiency in 109(64.9%), and sufficiency in 18(10.7%). The median HOMA-IR was 3.49(2.57, 5.14).Significant differences were found across vitamin D status groups for HOMA-IR [4.45(2.54, 6.62) vs. 3.58(2.74, 5.13) vs. 2.25(1.62, 3.40), P=0.003] and FINS[21.5(13.4, 30.1) mU/L vs. 16.5(13.0, 23.9) mU/L vs. 11.2(8.3, 17.8) mU/L, P=0.006], showing decreasing trends with improving vitamin D status. Spearman analysis revealed significant inverse correlations between serum 25(OH)D levels and FBG(r=-0.171, P=0.027), FINS(r=-0.234, P=0.002), and HOMA-IR(r=-0.250, P=0.001).After adjusting for age, sex, body mass index, and daily outdoor activity time, multivariate linear regression demonstrated that log-transformed 25(OH)D levels were independently and inversely associated with FBG(β=-0.324, P=0.022), lnFINS(β=-0.241, P=0.048), and lnHOMA-IR(β=-0.312, P=0.017).ConclusionsVitamin D deficiency/insufficiency is prevalent among pubertal adolescents, and serum vitamin D levels show a significant inverse association with insulin resistance. These findings suggest the potential importance of vitamin D status in metabolic health during puberty.