In this 5 year RCT among generally healthy and vitamin D-sufficient Finnish older adults, moderate- and high-dose vitamin D3 supplementation did not reduce the incidence of type 2 diabetes and, based on the subcohort data, did not have an effect on plasma glucose or insulin concentrations, HOMA-IR, BMI or waist circumference compared with placebo. Here, INS is linked to type 2 diabetes mellitus.