A sugar alcohol (also known as a polyol, polyhydric alcohol, or polyalcohol) is a hydrogenated form of carbohydrate, whose carbonyl group (aldehyde or ketone, reducing sugar) has been reduced to a primary or secondary hydroxyl group. They are commonly used for replacing sucrose in foodstuffs, often in combination with high intensity artificial sweeteners to counter the low sweetness. Some common sugar alcohols are:

• erythritol
• isomalt
• lactitol
• maltitol
• mannitol
• sorbitol
• xylitol
  

Disaccharides and monosaccharides can both form sugar alcohols; however, sugar alcohols derived from disaccharides (eg Maltitol and lactitol) are not entirely hydrogenated because only one aldehyde group is available for reduction.

Sugar alcohols as food additives:

As a group, sugar alcohols are not as sweet as sucrose, and they are also less caloric than sucrose. Their flavor is like sucrose, and they can be used to mask the unpleasant aftertastes of some high intensity sweeteners. In addition to their sweetness, some sugar alcohols can produce a noticeable cooling sensation in the mouth when highly concentrated, for instance in sugar-free hard candy ("boiled sweets") or chewing gum. Sugar alcohols are not metabolized by oral bacteria, and so they do not contribute to tooth decay. They do not brown and caramelize when heated.

Sugar alcohols are usually incompletely absorbed into the blood stream from the small intestines which generally results in a smaller change in blood glucose than "regular" sugar (sucrose). This property makes them popular sweeteners among diabetics and people on low-carbohydrate diets. However, as for many other incompletely digestible substances (such as dietary fiber), overconsumption of sugar alcohols can lead to bloating, diarrhea and flatulence because they are not absorbed in the small intestine. Some individuals experience such symptoms even in a single-serving quantity. With continued use, most people develop a degree of tolerance to sugar alcohols and no longer experience these symptoms. As an exception, erythritol is actually absorbed in the small intestine and excreted unchanged through urine, so it has no side effects at typical levels of consumption.