Sugar Alcohols: Why They're in Everything and What They Do

By the Strength from the Well Editorial Team · Evidence last reviewed September 2026 · Not reviewed by a licensed clinician (why we say that)

The short answer

Sugar alcohols are carbohydrates that taste sweet but are only partly absorbed by the body, which is why they provide fewer calories than sugar and raise blood sugar less. They are neither sugars nor alcohol in the drinking sense. The main ones you will see are erythritol, xylitol, maltitol, sorbitol and isomalt. Because the unabsorbed portion travels to the colon and is fermented by gut bacteria, they commonly cause gas, bloating and loose stools, with maltitol and sorbitol being the worst offenders and erythritol generally the best tolerated.

Key points

Sugar alcohols are partly absorbed carbohydrates, not sugars and not alcohol. They end in -ol on ingredient lists.
The unabsorbed portion ferments in the colon, which is what causes gas, cramping and diarrhea.
Erythritol is absorbed in the small intestine and excreted mostly unchanged, so it causes fewer digestive symptoms than the others.
Maltitol is the most common one in sugar-free candy and protein bars and is among the most likely to cause trouble.
Xylitol is seriously toxic to dogs, even in amounts that are harmless to people.
On a Nutrition Facts panel, sugar alcohols are counted inside total carbohydrate but are not added sugars, which is why 'net carb' math on the front differs from the panel.

What they actually are

Despite the name, sugar alcohols contain no ethanol and will not affect you the way a drink does. The term is chemical: these molecules have a structure related to both sugars and alcohols, with a hydroxyl group where a sugar would have something else. That structural difference is the whole story, because it is what makes them hard for your body to fully break down and absorb.

They occur naturally in small amounts in fruits and vegetables, and they are also manufactured at scale, usually by chemically modifying sugars from corn or birch. Most of what is in your protein bar is manufactured.

Because they are only partly absorbed, they contribute fewer calories per gram than sugar, ranging from almost none for erythritol up to about two-thirds of sugar's calories for maltitol. They also raise blood glucose less than sugar does, though not equally: erythritol has essentially no effect on blood sugar while maltitol has a substantial one, which matters a great deal if you are managing diabetes.

They are used heavily for reasons beyond sweetness. Unlike high-intensity sweeteners such as sucralose or stevia, sugar alcohols provide bulk, so they can physically replace sugar in a recipe and keep the texture of a candy, a bar or a gummy intact. That is why they show up in solid products far more than in beverages.

Why they upset your stomach

The mechanism is not mysterious and it is worth understanding, because it tells you which ones to expect trouble from.

Two things happen in the gut. First, sugar alcohols are osmotically active, meaning they pull water into the intestine. Second, whatever is not absorbed in the small intestine reaches the colon, where gut bacteria ferment it and produce gas. More water plus more gas produces exactly what you would predict: bloating, cramping, audible gurgling, urgency and loose stools. Some products in the European Union are required to carry a warning that excessive consumption may have a laxative effect, which is a fair description.

How much trouble a given sugar alcohol causes depends mostly on how much of it gets absorbed before the colon. Erythritol is the outlier: it is a small molecule that is largely absorbed in the small intestine and then excreted in urine mostly unchanged, so relatively little reaches the bacteria. That is why it is generally the best tolerated of the group, though large amounts can still cause symptoms.

Maltitol and sorbitol sit at the other end. Both are poorly absorbed, both ferment readily, and both are common in sugar-free candy, chocolate and protein bars. If a sugar-free product has ever sent you looking for a bathroom, maltitol is the most likely culprit.

People with irritable bowel syndrome are more sensitive to all of this. Sugar alcohols are polyols, the P in the FODMAP framework used to identify fermentable carbohydrates that trigger IBS symptoms, and they are among the most reliable triggers in that group.

Erythritol: best tolerated, minimal blood sugar effect, mostly excreted unchanged
Xylitol: moderately tolerated, tastes closest to sugar, toxic to dogs
Sorbitol: poorly absorbed, strong laxative effect, common in sugar-free gum and candy
Maltitol: very common, meaningful blood sugar effect, frequent cause of symptoms
Isomalt and lactitol: also poorly absorbed, mostly used in hard candy and baking

The dog problem, and other specific cautions

Xylitol is genuinely dangerous to dogs. In dogs it triggers a rapid insulin release that can cause severe low blood sugar and, at higher doses, liver failure. The amounts involved are small, and a dog getting into sugar-free gum, mints, peanut butter or a protein product is a veterinary emergency. This is not a mild caution and it is worth knowing if xylitol products are in your house.

Erythritol has drawn attention from research examining associations between higher blood levels and cardiovascular events. That work is early and observational in nature, and it does not establish that eating erythritol causes harm, partly because the body also produces erythritol internally. Regulatory bodies have not changed their assessment on the basis of it. The honest position is that this is unsettled and worth watching rather than a reason for alarm or for reassurance.

For anyone managing diabetes, the practical point is that sugar alcohols are not interchangeable. Maltitol raises blood glucose substantially more than erythritol does, and a product marketed as sugar-free can still move your numbers. Blood glucose response is individual, and checking is more informative than trusting the front of a box.

How to find them on a label

The easy tell is the ending. Erythritol, xylitol, sorbitol, maltitol, mannitol, isomalt and lactitol are the ones you will actually encounter, and most of them end in -ol.

On a Nutrition Facts panel, sugar alcohols are part of total carbohydrate. They may be listed on their own line labeled 'Sugar Alcohol', which manufacturers can include voluntarily and must include if the product makes a claim about them. They are not counted as added sugars, which is why a product can honestly say zero added sugar while being built almost entirely on maltitol.

'Net carbs' is a marketing calculation, not a regulated term. It typically means total carbohydrate minus fiber minus sugar alcohols. That subtraction is roughly reasonable for erythritol and considerably less reasonable for maltitol, which is partly absorbed and does affect blood sugar. Take the number as an estimate made by the seller.

Check the placement in the ingredient list, since ingredients are ordered by weight. A sugar alcohol appearing first or second means the product is substantially made of it. And check the serving size honestly. Many bars and bags of gummies list a serving that is half of what a person eats in one sitting, which doubles the dose of whatever is in there.

There is no villain here. Sugar alcohols solved a real problem for people who want sweetness without sugar, and for many people they work fine. But they are the most common reason a low-sugar product makes someone feel terrible, and nobody prints that on the front. Knowing which name is on your label is the difference between blaming the protein, blaming your gut, and knowing what actually happened.

Common questions

Which sugar alcohol is least likely to upset my stomach?

Erythritol, in general. It is absorbed in the small intestine and excreted largely unchanged, so less of it reaches the colon to be fermented. Large amounts can still cause symptoms, and individual tolerance varies, but it is consistently the best tolerated of the group.

Do sugar alcohols count as carbs if I am counting?

They are carbohydrates and are included in total carbohydrate on the panel. How much they affect blood sugar varies widely by type, with erythritol having almost no effect and maltitol having a substantial one. The 'net carb' figure on the front is the manufacturer's estimate, not a regulated number.

Are sugar alcohols safe?

The main established effect is digestive, and it is dose dependent rather than dangerous. Regulatory agencies consider the common sugar alcohols acceptable for use in food. Research on erythritol and cardiovascular markers is ongoing and currently inconclusive, and xylitol is a serious poisoning risk for dogs though not for people.

Why does the same amount bother me some days and not others?

Tolerance depends on what else is in your gut, how fast things are moving, your gut bacteria, and whether you ate the product on an empty stomach. Symptoms are also cumulative across a day, so a gummy in the morning and a bar in the afternoon can add up to a dose neither would reach alone.

Sources

This is information, not medical advice. Strength from the Well is an independent publisher. Nothing here is a diagnosis, a prescription, or a recommendation to start or stop any treatment. Talk to a clinician who knows your history before you act on anything you read here — including anything you read here that contradicts them.