Though the study is preliminary—read: no reason to fill your fridge with mangos just yet—one sliced cup of the fruit only contains 100 calories, and is a healthy add-on to any diet. But your best bet to keep blood sugar in check? Exercise and a diet generally rich in all sorts of fruits and vegetables, says Lucas. In fact, people who ate produce-packed diets had a decreased diabetes risk and lower blood sugar levels than those who didn’t, according to a 2012 meta-analysis.