When blood sugar levels rise too high, sugar sticks to the surface membranes of cells. The sugar, glucose, is converted into another sugar, fructose, and eventually to sorbitol, which destroys the cells. This cell damage leads to heart attacks, strokes, blindness, deafness, kidney damage and the other harmful effects of diabetes.
The same chemical is harmless when it is used in foods because you do not absorb it. Sugar alcohols such as sorbitol, mannitol or xylitol have almost the same chemical structures as carbohydrates, but they have an alcohol end on one side. This prevents them from being absorbed from your intestines, so they can be used to sweeten food without contributing any calories. The sugar alcohols pass undigested to your colon where they are fermented by bacteria, so large amounts can cause gas and diarrhea. That's why sorbitol is used only in foods such as hard candy or gum, where portion sizes are very small. How to keep blood sugar levels from rising too high; how to recognize pre-diabetes