Tufts University Apr 23 2026 More than two in five U.S. adults has prediabetes, a condition marked by higher-than-normal blood sugar levels that often leads to type 2 diabetes. A new study finds that vitamin D may help delay or prevent that progression, but only in people with certain genetic variations. The study, published today in JAMA Network Open , found prediabetic adults with certain variations in the vitamin D receptor gene had a 19% lower risk of developing diabetes when taking a high