INS and vitamin D deficiency: Bayani et al showed that vitamin D concentration was significantly lower in diabetic patients compared with that in healthy individuals.[4] Moreover, animal and human studies have demonstrated a correlation between vitamin D deficiency and impaired insulin production and secretion as well as insulin sensitivity.[5,6,7] Another study reported that reduced serum insulin levels could be related to the lower level of 1,25(OH)2 D.[8]