Serum Vitamin D Concentrations Are Not Associated with Insulin Resistance in Swiss

Background: Low vitamin D status has been associated with an increased risk of developing type 2 diabetes and insulin resistance (IR), although this has been recently questioned. Objective: We examined the association between serum vitamin D metabolites and incident IR. Methods: This was a prospective, population-based study derived from the CoLaus (Cohorte Lausannoise) study including 3856 participants (aged 51.26 10.4 y; 2217women) free from diabetes or IR at baseline. IR was defined as a homeostasis model assessment (HOMA) index>2.6. Fasting plasma insulin and glucose were measured at baseline and at follow-up to calculate the HOMA index. The association of vitamin D metabolites with incident IR was analyzed by logistic regression, and the results were expressed for each independent variable as ORs and 95 % CIs. Results: During the 5.5-y follow-up, 649 (16.9%) incident cases of IR were identified. Participants who developed IR had lower baseline serum concentrations of 25-hydroxyvitamin D3 [25(OH)D3 (25-hydroxycholecalciferol); 45.96 22.8 vs. 49.96 22.6 nmol/L; P < 0.001], total 25(OH)D3 (25(OH)D3 + epi-25-hydroxyvitamin D3 [3-epi-25(OH)D3]; 49.16 24.3 vs. 53.36 24.1 nmol/L; P < 0.001), and 3-epi-25(OH)D3 (4.26 2.9 vs. 4.36 2.5 nmol/L;P = 0.01) but a higher 3-epi- to total 25(OH)D3 ratio (0.096 0.05 vs. 0.086 0.04; P = 0.007). Multivariable analysis adjusting for month of sampling, age, and sex showed an inverse association between 25(OH)D3 and the likelihood of developing IR [ORs (95%CIs): 0.86 (0.68, 1.09), 0.60 (0.46, 0.78), and 0.57 (0.43, 0.75) for the second, third, an