Sugar alcohols or "polyols," as they are also called, are neither sugars nor alcohols. They are carbohydrates with a chemical structure that partially resembles sugar and partially resembles alcohol . They occur naturally in plant products such as fruits and berries but are commercially produced from other carbohydrates such as sucrose (table sugar), glucose, and starch. Their calorie content us usually around 2 calories per gram compared to 4 calories per gram for sucrose or other naturally sweet sugars. Most are approximately half as sweet as sucrose. They do not cause tooth decay like sugar does. Therefore, many "sugar-free" gums are made with sugar alcohols. Sugar alcohols also add texture to foods, retain moisture better and prevent foods from browning when they are heated.

Because they are absorbed into the bloodstream more slowly than sugar, sugar alcohols don't raise blood sugar levels as high or as fast as simple sugars and they require little or no insulin to be metabolized. Therefore, people with diabetes sometimes use them as sugar alternatives.

The most commonly used sugar alcohols are mannitol and sorbitol, which can be found in hard and soft candies, cookies, and cake mixes. They are frequently used in toothpaste and mouthwash too. Other sugar alcohols are xylitol and isomalt. They are safe sweeteners but are not well absorbed and consuming large amounts of them (about 50 grams of sorbitol or about 20 grams of mannitol) can cause diarrhea. Products containing large amounts of mannitol and sorbitol must carry the warning, "Excess consumption may have a laxative effect."