Vitamin D intake associates with insulin resistance in type 2 diabetes, but not in latent autoimmune diabetes in adults

This study aimed to evaluate the relationship between vitamin D (vitD) intake and serum concentrations and insulin secretion (assessed by C-peptide serum concentration)/insulin resistance (determined by estimated glucose disposal rate [eGDR]) in patients with latent autoimmune diabetes in adults (LADA) and type 2 diabetes (T2DM). C-peptide, serum vitD, lipid profile, insulin, glucose, and glycosylated hemoglobin (HbA1c) were assessed; vitD intake was determined; and eGDR was calculated. Groups were compared using the Student t or Mann-Whitney U test. Correlations were performed between insulin secretion, insulin resistance, and vitD, and linear regression models were adjusted for confounding variables. Of 107 patients included, age was 55.3 ± 11.84 years old, and time since diabetes diagnosis was 13.23 ± 5.96 years. There were significant intergroup differences in age, body mass index (BMI), hip measurements, glucose, and HbA1c. The correlation between vitD intake and C-peptide for the whole group was significant (r = 0.213; P = .032) as well as for vitD deficiency/sufficiency in T2DM (P = .042), whereas neither was significant in eGDR. After adjustment for age, HbA1c, disease progression, physical activity, solar exposure, sex, and BMI, vitD intake was only significant in T2DM (P = .028). In serum vitD, only the correlation between eGDR and vitD in T2DM was significant and intragroup when comparing vitD sufficiency. After adjustments, significance was lost. Patients with LADA had lower intake of vitD, poorer metabolic control, lower BMI, and younger age compared to T2DM patients. There was no association between serum vitD or vitD intake and insulin secretion when analyzed by group, although vitD intake was associated with insulin resistance in T2DM, but not LADA.