Mannitol

Sugar-free sweetener: "Dust" on chewing gum, other sugar-free foods.
Mannitol, like most other sugar alcohols, is not as sweet as sugar, not absorbed well by the body (which means it provides only less than half as many calories per gram as table sugar), and does not promote tooth decay. However, large amounts may have a laxative effect and may even cause diarrhea. The FDA requires foods "whose reasonably foreseeable consumption may result in a daily ingestion of 20 grams of mannitol" to bear this warning: "Excess consumption may have a laxative effect."