GSTM1 and type 2 diabetes mellitus: Mitri et al. [14] implemented a 2-by-2 factorial-designed, double-masked, placebo-controlled trial and discovered that cholecalciferol (2000 IU once daily) supplementation for 16 wk can improved β cell function and had a marginal effect on attenuating the rise in Hb A(1c) in adults at risk of type 2 diabetes.