INS and type 2 diabetes mellitus: While association studies postulate a possible effect of vitamin D supplementation on fasting glucose, HbA1c, and insulin resistance in type II diabetes mellitus [44], randomized controlled trials have shown no influence of vitamin D supplements on the rate of progression from prediabetes to type II diabetes mellitus [45] on the risk of developing type II diabetes mellitus at low vitamin D concentrations [46], glucose-insulin metabolism [47], or insulin resistance in children [48].