GSTM1 and Insulin resistance: Compared with the placebo group, fasting plasma glucose, 2-hr post-prandial blood glucose, glycosylated hemoglobin(Hb A1C), serum insulin level, and homeostasis model of assessment-estimated insulin resistance(HOMA_IR) were not significantly changed in the selenium group at the end of study (p = 0.25, p = 0.87, p = 0.34, p = 0.57, and p = 0.31, respectively).