Sugar Alcohol

What Are Sugar Alcohols?

Sugar alcohols, also called polyols, are a class of carbohydrates that are chemically derived from sugars but contain a hydroxyl group (-OH) in place of the aldehyde or ketone group found in conventional sugars. Despite the name, they contain no ethanol and are safe for consumption. Sugar alcohols occur naturally in small amounts in fruits and vegetables but are also manufactured commercially for use as reduced-calorie sweeteners and humectants in food products.

Common sugar alcohols used in food include:

• Xylitol — from birch wood and corn cobs; approximately 2.4 kcal/g
• Erythritol — fermented from glucose; approximately 0.2 kcal/g
• Sorbitol — from glucose reduction; approximately 2.6 kcal/g
• Mannitol — from fructose reduction; approximately 1.6 kcal/g
• Maltitol — from maltose; approximately 2.1 kcal/g
• Lactitol — from lactose; approximately 2.0 kcal/g
• Isomalt — from sucrose; approximately 2.0 kcal/g

Digestion and Blood Sugar Impact

Sugar alcohols are partially or minimally absorbed in the small intestine, which accounts for their lower caloric values compared to regular sugars (4 kcal/g). The fraction that is not absorbed passes into the large intestine, where gut bacteria ferment it. Because absorption is incomplete, sugar alcohols produce a smaller rise in blood glucose and insulin compared to equivalent amounts of sugar, making them popular in products marketed to people with diabetes or those following low-carbohydrate diets.

Erythritol is unique among sugar alcohols: approximately 90% is absorbed in the small intestine and excreted unchanged in the urine, resulting in negligible caloric contribution and minimal fermentation in the colon.

Gastrointestinal Effects and Labeling

The colonic fermentation of unabsorbed sugar alcohols can cause gastrointestinal symptoms — particularly bloating, gas, and diarrhea — in sensitive individuals or when consumed in large amounts. Sorbitol and mannitol are most commonly associated with these effects. Erythritol is generally well tolerated at moderate intakes.

In the United States, sugar alcohols must be listed on the Nutrition Facts label under "Total Carbohydrate." The FDA requires a laxative warning statement on food packages that contain more than 50 grams of sorbitol or more than 20 grams of mannitol per day's consumption. Despite their reduced glycemic impact, sugar alcohols are not calorie-free and should be accounted for in overall dietary planning.