Sorbitol is a polyol or sugar-alcohol. It is a sugar substitute and has a relatively weak effect on blood glucose concentrations. It is particularly found in "no added sugar" sweets, "sugar free" chewing gum, and some "no added sugar" fruit tarts and frozen deserts. Once eaten, sorbitol is only partly absorbed by the body. For this reason it provides approximately half as many calories as table sugar.
However, the sweetening potency of sorbitol is slightly less than that of sucrose (cf. fructose). When it is used in a product larger amounts need to be added to obtain a similar sweetness to that obtained using sugar. This means that a sweet sweetened with sorbitol, for example, provides almost the same number of calories as a regular sweet, although it has a smaller effect on blood glucose concentrations.
Chemical formula of sorbitol. DR Credits