Interestingly, within the group of test participants that increased their vitamin D3 intake (rather than eldecalcitol), those that maintained a vitamin D blood serum level of 50 ng/ml or higher (i.e., the truly optimal vitamin D level we should be aiming for, according to experts) during the three-year follow-up reduced their diabetes risk by a whopping 76% compared to participants that had serum levels of 20 to 29 ng/ml (i.e., clinical insufficiency).