Sugar alcohols are a type of sweetener found naturally in some fruits and vegetables and added to thousands of “sugar-free” and “reduced sugar” products. Despite the name, they contain neither sugar nor alcohol in the way most people understand those words. They’re a hybrid molecule: structurally similar to sugar but with a small chemical tweak that changes how your body absorbs and processes them. That tweak means fewer calories, a much smaller blood sugar spike, and in some cases, real benefits for your teeth.
How They Differ From Sugar
Regular table sugar (sucrose) has 4 calories per gram. Sugar alcohols range from 1.5 to 3 calories per gram, depending on the type. The calorie reduction comes from the way their molecules are built. In an ordinary sugar molecule, one end features a reactive chemical group that your body breaks down efficiently for energy. In a sugar alcohol, that reactive group has been swapped out, which means your digestive enzymes can’t process the molecule as completely. The result: you absorb less energy from it.
This same structural change is why sugar alcohols taste sweet but not quite as sweet as sugar. Most land somewhere between 50% and 97% of sugar’s sweetness, with maltitol at the top of that range and lactitol near the bottom. They also don’t brown foods the way sugar does, because the chemical reaction responsible for caramelization and browning (the Maillard reaction) requires the reactive group that sugar alcohols lack.
Common Types and How They Compare
You’ll encounter several sugar alcohols on ingredient lists. Each behaves a little differently in your body:
- Erythritol: About 63% as sweet as sugar. Glycemic index of 1, meaning it has virtually no effect on blood sugar. Roughly 90% of it is absorbed in the small intestine and excreted unchanged in urine, which also makes it the easiest on your stomach.
- Xylitol: 97% as sweet as sugar, making it the closest substitute in taste. Glycemic index of 12. Well known for dental benefits, and the most common sugar alcohol in chewing gum.
- Sorbitol: 58% as sweet as sugar. Glycemic index of 4. One of the most widely produced sugar alcohols globally, with around 700,000 tons manufactured per year through an industrial process that converts glucose.
- Maltitol: 87% as sweet as sugar. Glycemic index of 35, which is the highest of the group and close enough to sugar’s GI of 65 that people watching their blood sugar should be cautious with it.
- Isomalt: 54% as sweet as sugar. Glycemic index of 2. Often used in hard candies because it resists crystallization.
- Lactitol: 35% as sweet as sugar. Glycemic index of 3. The least sweet option, typically combined with other sweeteners.
For reference, table sugar has a glycemic index of 65. Most sugar alcohols fall between 1 and 12, making them a genuinely lower-glycemic option. Maltitol is the outlier at 35.
What Happens When You Eat Them
Your body handles sugar alcohols very differently from regular sugar. Only a portion gets absorbed in the small intestine, and that portion varies widely by type. Lactitol, for instance, passes through the small intestine largely unabsorbed, with about 84% reaching the colon. Maltitol and isomalt are partially absorbed, with roughly 40 to 44% making it to the colon. Erythritol sits at the opposite end, with about 90% absorbed before it ever reaches the large intestine.
Whatever isn’t absorbed in the small intestine travels to the colon, where gut bacteria ferment it. This fermentation produces gas and draws water into the intestine, which is exactly why sugar alcohols can cause bloating, cramping, and diarrhea if you eat too much. The bacteria do eventually break down the sugar alcohols completely, so the unabsorbed portion isn’t wasted. It still provides some calories, just fewer than if it had been absorbed directly.
Digestive Side Effects
The laxative effect is the most common complaint, and tolerance varies by both the type of sugar alcohol and the person eating it. Research has measured the thresholds fairly precisely. Sorbitol triggers diarrhea at relatively low doses: around 0.17 grams per kilogram of body weight for men and 0.24 grams per kilogram for women. For a 70 kg (154 lb) man, that’s only about 12 grams of sorbitol, roughly the amount in two or three “sugar-free” candy bars.
Erythritol is far more forgiving. Its laxative threshold is about 0.66 grams per kilogram for men and 0.80 grams per kilogram for women. For that same 70 kg man, that works out to around 46 grams before digestive trouble starts. This higher tolerance is directly related to erythritol’s absorption rate: since 90% of it gets picked up in the small intestine, much less reaches the colon to cause problems.
If you’re new to sugar alcohols, starting with small amounts and increasing gradually gives your gut bacteria time to adapt. Spreading intake throughout the day rather than consuming a large amount at once also helps.
Benefits for Dental Health
Sugar alcohols don’t feed the bacteria that cause cavities, and xylitol actively fights them. The cavity-causing bacterium Streptococcus mutans absorbs xylitol the same way it absorbs regular sugar, but once inside the cell, xylitol can’t be used for energy. Instead, the bacterium spends energy pulling xylitol in, converting it, and then expelling it, gaining nothing in return. This “futile energy cycle” essentially starves the bacteria, inhibiting their growth and eventually killing them.
Xylitol also reduces the acidity of dental plaque by increasing concentrations of ammonia and amino acids that neutralize plaque acids. Over time, bacteria exposed to xylitol develop resistant strains that are less capable of causing damage in the mouth. This is why xylitol-sweetened gum is often recommended by dentists, not just as a sugar-free alternative, but as an actively protective one.
The Erythritol Heart Health Question
A widely reported study from the Cleveland Clinic found that people with higher blood levels of erythritol had an increased risk of heart attack, stroke, and early death. This research raised legitimate questions, particularly since erythritol is one of the most popular sugar alcohols in keto, low-carb, and stevia-based products.
The study showed an association, not a direct cause-and-effect relationship. Your body actually produces small amounts of erythritol on its own during normal metabolism, and blood levels can rise for reasons unrelated to diet. Many of the study participants already had existing heart disease risk factors. Still, the findings are worth noting, especially for people who consume erythritol daily in large quantities. More work is needed to clarify whether the erythritol itself is contributing to risk or simply showing up alongside other factors.
How to Spot Them on Labels
Under FDA rules, sugar alcohols don’t have to appear on a nutrition label unless the product makes a claim about sugar content, total sugars, or added sugars. When sugar alcohols are present and listed, they appear as a separate line item, indented under total carbohydrates, expressed in grams per serving. If only one type of sugar alcohol is in the product, the label can name it specifically (for example, “xylitol” instead of “sugar alcohol”).
On ingredient lists, look for names ending in “-ol”: sorbitol, xylitol, maltitol, erythritol, mannitol, lactitol, and isomalt. Hydrogenated starch hydrolysates, sometimes listed as HSH, are another form. Products labeled “sugar-free” or “no sugar added” almost always contain sugar alcohols, artificial sweeteners, or both.
Xylitol Is Toxic to Dogs
This is not a minor footnote. Xylitol is life-threatening to dogs at doses that would be trivial for a human. Dogs that ingest more than 0.1 grams per kilogram of body weight risk dangerously low blood sugar. At doses above 0.5 grams per kilogram, acute liver failure becomes a real possibility. For a 10 kg (22 lb) dog, that’s just 1 gram for hypoglycemia risk and 5 grams for liver damage, an amount easily found in a few sticks of sugar-free gum.
The difference comes down to biology. In dogs, xylitol triggers a massive insulin release that doesn’t happen in humans. If your dog gets into a product containing xylitol, it’s a veterinary emergency. The prognosis is good if only blood sugar drops, but guarded to poor once the liver is involved.