IRANIAN DIABETICS MAY NOT BE VITAMIN D DEFICIENT MORE THAN HEALTHY SUBJECTS

There are some reports of decreased serum levels of 25(OH)D in the subjects with impaired glucose tolerance and type 2 diabetes mellitus (T2DM). To assess vitamin D status of the Iranian diabetics, a pilot study was conducted on 90 subjects with either type 1 diabetes mellitus (T1DM) (n= 30), T2DM (n= 30), or apparently healthy subjects (n= 30) during fall and winter of 2005. Serum samples were analyzed for 25-hydroxycholecalciferol using three different methods: high-performance liquid chromatography (HPLC), competitive protein-binding assay (CPBA) and radioimmunoassay (RIA). In this study serum levels of 25(OH)D were categorized as follows: sufficient ≥ 37 nmol/L; 25 nmol/L ≤ mild deficiency < 37 nmol/L; 12.5 nmol/L ≤ moderate deficiency < 25 nmol/L; severe deficiency < 12.5 nmol/L. Results showed that the occurrence of vitamin D insufficiency was almost the same in patients with T1DM and healthy controls. Mean serum level of 25(OH)D in patients with T2DM was significantly higher than in T1DM, as judged by HPLC (58.2 ± 8.5 vs. 35 ± 5 nmol/L, Mann Whitney U-Wilcoxon, P= 0.024). Moreover, both CPBA and RIA showed some over-estimation of serum 25(OH)D compared to HPLC. Our findings suggest that, at least in the cold seasons, vitamin D status of the healthy subjects may not be higher than that of T1DM patients.