Vitamin D and diabetes in Koreans: analyses based on the Fourth Korea National Health and Nutrition Examination Survey (KNHANES), 2008–2009

Abstract

AimsA causal relationship between vitamin D deficiency and the incidence of diabetes mellitus has been suggested, but little research has been conducted on the Korean population.MethodsWe analysed the glucose tolerance status and serum 25-hydroxyvitamin D concentrations in 12 263 subjects > 19 years old who were registered for the Korea National Health and Nutrition Examination Survey, 2008–2009.ResultsVarious demographic variables such as gender, age, season, resident area, physical activity, smoking, alcohol, marital status, education and occupation were associated with serum 25-hydroxyvitamin D concentrations. After adjusting for these variables as confounders, 25-hydroxyvitamin D concentrations in subjects with diabetes were significantly lower than those in subjects with normal glucose tolerance and those with impaired fasting glucose (P = 0.005). Compared with the ≥ 75 nmol/l subgroup of serum 25-hydroxyvitamin D concentration, the odds ratios and 95% confidence intervals for diabetes mellitus were 1.206 (95% CI 0.948–1.534) in the 50- to 74-nmol/l subgroup, 1.339 (1.051–1.707) in the 25- to 49-nmol/l subgroup and 1.759 (1.267–2.443) in the < 25-nmol/l subgroup. Compared with the serum ≥ 75-nmol/l 25-hydroxyvitamin D subgroup, serum insulin and homeostasis model assessment 2%B, a marker of insulin secretory capacity, were significantly higher, and homeostasis model assessment 2%S, a marker of insulin sensitivity, was significantly lower in the < 25- and 25- to 49-nmol/l serum 25-hydroxyvitamin D subgroups than those in the other subgroups (P < 0.001).ConclusionsThe findings suggest that vitamin D deficiency, possibly involving altered insulin sensitivity, is associated with an increased risk for diabetes mellitus in the Korean population.