Vitamin D doesn't prevent type 2 diabetes

Morning Rounds loves a negative study, and in this one, researchers reported that that a daily vitamin D supplement did not stave off type 2 diabetes. Scientists had previously noticed an association between lower levels of vitamin D and type 2 diabetes, and some studies had indicated vitamin D could bolster the activity of insulin-generating beta cells. But in the new trial, which involved more than 2,400 people with signs of prediabetes, those who took a daily boost of vitamin D did not have significantly lower rates of diabetes after a few years than those who took a placebo. The results of the “D2d study” highlight the importance of running trials to answer questions raised by correlative work.