Sugar alcohols are a type of sweetener derived from sugars, used widely in “sugar-free” and “low-carb” foods. Despite the name, they contain neither alcohol in the drinking sense nor sugar in the traditional sense. They’re a hybrid: sweet-tasting compounds that your body only partially absorbs, which is why they have fewer calories and a smaller effect on blood sugar than regular sugar. You’ll find them listed on ingredient labels as sorbitol, xylitol, erythritol, maltitol, mannitol, isomalt, and lactitol.
Why They’re Called “Alcohols”
The “alcohol” in sugar alcohol refers to a specific chemical structure, not the ethanol in beer or wine. In chemistry, an alcohol is any molecule with a particular type of oxygen-hydrogen group attached to it. Regular sugar has one of these groups, but sugar alcohols have several, which is why chemists also call them “polyols” (meaning many alcohol groups). This structural tweak is what changes how your body processes them. They taste sweet because they’re close enough to sugar for your taste buds to recognize, but different enough that your digestive enzymes can’t fully break them down.
Where Sugar Alcohols Show Up
Sugar alcohols are found naturally in small amounts in fruits like pears, melons, and grapes, as well as in fermented foods. Commercially, they’re manufactured through a chemical process that converts sugars into their corresponding alcohol form. You’ll encounter them in sugar-free gum, candy, ice cream, protein bars, baked goods, cough drops, toothpaste, and many products marketed toward keto or low-carb diets. On a nutrition label, they appear under “Total Carbohydrates” with their own line item.
Calories and Sweetness Compared to Sugar
Regular table sugar delivers 4 calories per gram. Sugar alcohols range from 1.5 to 3 calories per gram, depending on the type. That’s a meaningful reduction, but not zero, which is an important distinction from artificial sweeteners like aspartame or sucralose that are truly calorie-free.
Their sweetness levels vary quite a bit:
- Xylitol is about as sweet as sugar, gram for gram.
- Maltitol reaches about 75% of sugar’s sweetness.
- Erythritol hits 60 to 80% of sugar’s sweetness, with essentially zero calories.
- Sorbitol is only 50% as sweet as sugar, so products need twice as much to taste comparable.
- Isomalt reaches 45 to 65% of sugar’s sweetness and is often blended with other sweeteners to compensate.
How They Affect Blood Sugar
This is the main reason sugar alcohols are popular with people managing diabetes or following low-carb diets. Because your small intestine only partially absorbs them, they cause a much smaller spike in blood sugar and insulin compared to regular sugar. The glycemic index of table sugar is 69. For sugar alcohols, the numbers are dramatically lower: maltitol sits at 35, xylitol at 13, sorbitol at 9, and both erythritol and mannitol register at 0. That last number means erythritol and mannitol pass through your system without raising blood glucose or triggering insulin at all.
These properties also make sugar alcohols less likely to promote fat storage, since they stimulate less insulin production than sugar does.
Counting Net Carbs on Labels
If you track carbohydrates, sugar alcohols change the math. The standard approach is to subtract fiber and sugar alcohols from total carbohydrates to get “net carbs,” the carbs your body actually absorbs. For erythritol, you can subtract the full amount. For other sugar alcohols like maltitol or sorbitol, it’s safer to subtract only half, since your body does absorb a portion of them. So a food with 20 grams of total carbs, 8 grams of fiber, and 4 grams of erythritol would have 8 net carbs.
Digestive Side Effects
The fact that sugar alcohols aren’t fully absorbed is both their advantage and their biggest drawback. The unabsorbed portion travels to your large intestine, where gut bacteria ferment it and where it draws water into the bowel through osmosis. The result, for many people, is gas, bloating, cramping, and diarrhea. This is common enough that the FDA requires a laxative warning on products where you might reasonably consume 50 grams of sorbitol in a day.
Tolerance thresholds vary by type. Sorbitol and mannitol can cause digestive changes in adults at just 10 to 20 grams per day, with 20 to 50 grams of sorbitol enough to trigger osmotic diarrhea in most people. Maltitol is somewhat better tolerated: 30 grams in chocolate caused no significant symptoms in one study, while 40 grams produced mild gas but no diarrhea. At 45 grams, though, 85% of participants experienced diarrhea.
Erythritol is the gentlest option. Because it’s absorbed in the small intestine and excreted through urine rather than reaching the colon, it typically causes no gastrointestinal symptoms at normal consumption levels.
Benefits for Dental Health
Sugar alcohols don’t cause cavities. In fact, xylitol actively fights them. The bacteria responsible for tooth decay can take up xylitol but can’t use it for energy. This traps the bacteria in a wasteful cycle that eventually kills them. Xylitol also reduces plaque formation, limits bacterial attachment to teeth, and decreases acid production that erodes enamel. This is why xylitol is a common ingredient in sugar-free gum and dental products.
Erythritol and Heart Health Concerns
A study published by researchers at the Cleveland Clinic found that people with higher blood levels of erythritol had an increased risk of heart attack, stroke, and early death. This finding raised concern because erythritol is one of the most widely used sugar alcohols, showing up in stevia blends, monk fruit sweeteners, and many keto-friendly products. The research is still in early stages, and it’s not yet clear whether erythritol directly causes cardiovascular problems or whether high blood levels are a marker of something else. But for people who consume erythritol daily and in large amounts, it’s worth paying attention to as more data emerges.
Xylitol Is Dangerous for Dogs
One critical safety note: xylitol is extremely toxic to dogs. A dose as small as 0.1 grams per kilogram of body weight can cause a dangerous drop in blood sugar, and anything above 0.5 grams per kilogram can trigger acute liver failure. For a 20-pound dog, that’s less than a gram to reach the danger zone. Peanut butter, gum, candy, and baked goods sweetened with xylitol are all potential hazards. If your dog eats something containing xylitol, it’s a veterinary emergency.