Sugar alcohols are not inherently bad for you, but they come with trade-offs worth understanding. These sweeteners, found in sugar-free gums, protein bars, and keto-friendly snacks, have real advantages over regular sugar: they barely raise blood sugar, contain fewer calories, and some even protect your teeth. But they can also cause digestive problems, and newer research on one popular type has raised serious questions about heart health.
What Sugar Alcohols Actually Are
Despite the name, sugar alcohols contain no alcohol and aren’t exactly sugar. They’re a class of carbohydrates with a chemical structure that partially resembles both sugar and alcohol, which is how they got the confusing label. Your body absorbs them incompletely, which is why they deliver sweetness with fewer calories and less impact on blood sugar than regular table sugar.
The most common sugar alcohols you’ll encounter are xylitol, erythritol, sorbitol, and maltitol. You’ll find them in products labeled sugar-free, keto-safe, diabetes-friendly, or low sugar. They show up in chewing gum, candy, ice cream, protein bars, baked goods, and even toothpaste. If a packaged food claims to be sugar-free but still tastes sweet, there’s a good chance it contains one of these.
The Blood Sugar Advantage
This is the main reason sugar alcohols exist in so many products. Regular table sugar (sucrose) has a glycemic index of 69, meaning it causes a substantial spike in blood sugar after you eat it. Most sugar alcohols sit dramatically lower. Erythritol and mannitol have a glycemic index of zero. Xylitol comes in at 13, sorbitol at 9, and even maltitol, the highest of the group, only reaches 35.
The insulin response follows the same pattern. Sucrose triggers an insulinemic index of 48, while erythritol barely registers at 2, xylitol at 11, and mannitol at zero. For people managing diabetes or trying to reduce blood sugar spikes, this difference is meaningful. It’s also why sugar alcohols get subtracted from total carbohydrates in “net carb” calculations popular in keto dieting, though it’s worth noting the FDA doesn’t officially recognize the net carbs concept, and the math isn’t always precise.
Maltitol deserves a special mention here. With a glycemic index of 35 and an insulin response of 27, it’s the sugar alcohol that behaves most like actual sugar. If blood sugar control is your goal, check which sugar alcohol you’re actually eating. Not all of them perform equally.
Digestive Side Effects
The most common complaint about sugar alcohols is that they can cause gas, bloating, cramping, and diarrhea. This happens because your small intestine doesn’t fully absorb them. The unabsorbed portion travels to your large intestine, where gut bacteria ferment it and produce gas. Eat enough, and the osmotic effect draws water into your intestine, triggering loose stools.
How much is “enough” varies by the specific sugar alcohol and your body weight. Sorbitol is the most likely to cause problems: as little as 0.17 grams per kilogram of body weight in men (about 13 grams for a 170-pound person) can trigger a laxative effect. Erythritol is far more forgiving because roughly 90% of it gets absorbed in the small intestine before reaching the colon. The laxative threshold for erythritol is around 0.66 grams per kilogram in men and 0.80 grams per kilogram in women, roughly four times higher than sorbitol’s threshold.
Products containing sorbitol that could reasonably lead to consuming 50 grams in a day are required by the FDA to carry the warning: “Excess consumption may have a laxative effect.” Your tolerance also improves with repeated exposure. People who eat sugar alcohols regularly tend to handle larger amounts than first-timers. Starting with small portions and increasing gradually is a practical way to reduce discomfort.
The Erythritol Heart Risk Question
A 2023 study published in Nature Medicine raised a significant concern about erythritol specifically. Researchers tracked over 1,000 people and found that those with the highest blood levels of erythritol were about twice as likely to experience a heart attack, stroke, or cardiovascular death over three years compared to those with the lowest levels.
The researchers then investigated why. When they exposed human blood platelets to erythritol in the lab, the platelets became more sensitive to clotting signals. In mice, elevated erythritol levels sped up blood clot formation and artery blockage. Perhaps most striking: when eight healthy volunteers drank a beverage sweetened with erythritol, their blood levels of the compound surged 1,000-fold and stayed elevated for several days. For at least two of those days, levels were high enough to trigger the platelet changes seen in the lab.
This doesn’t prove that erythritol causes heart attacks. The initial finding was observational, meaning it shows a correlation, not necessarily cause and effect. People with metabolic problems may naturally produce more erythritol in their bodies, which could explain part of the link. But the lab and animal data showing a plausible clotting mechanism make this more than a statistical fluke. If you have existing cardiovascular risk factors, this research is worth paying attention to.
Dental Benefits of Xylitol
Not all the news is negative. Xylitol actively fights tooth decay, which is why it’s a common ingredient in sugar-free gum and toothpaste. The cavity-causing bacteria in your mouth (mutans streptococci) can’t use xylitol for energy the way they use regular sugar. When they try, it disrupts their energy production and eventually kills the cells. Xylitol also reduces plaque formation, limits the bacteria’s ability to stick to tooth surfaces, and decreases the acid production that erodes enamel.
This isn’t a minor benefit. Regular xylitol exposure through gum or mints meaningfully reduces the bacterial population most responsible for cavities. It’s one of the few cases where a sugar substitute does something genuinely positive beyond simply replacing sugar.
A Serious Danger for Dogs
If you have a dog, this may be the most important thing in this article. Xylitol is extremely toxic to dogs. A dose as small as 0.1 grams per kilogram of body weight can cause dangerous drops in blood sugar, and anything above 0.5 grams per kilogram can trigger acute liver failure. For a 20-pound dog, that could mean just a couple of pieces of xylitol-sweetened gum. Symptoms include vomiting, loss of coordination, and collapse. If your dog gets into a product containing xylitol, it’s a veterinary emergency.
How to Think About Sugar Alcohols Overall
Sugar alcohols are substantially better than regular sugar for blood sugar control, and they provide fewer calories. That’s a genuine benefit, especially if you’re managing diabetes or reducing sugar intake. Xylitol offers a real bonus for dental health. The digestive side effects are manageable for most people once they learn their personal tolerance and stick within it.
The erythritol cardiovascular findings, however, introduce real uncertainty. Erythritol had been considered the “safest” sugar alcohol because of its high digestive tolerance and zero glycemic impact. The clotting data complicates that reputation. It doesn’t mean you need to panic over a piece of sugar-free candy, but regularly consuming large amounts of erythritol, particularly if you already have heart disease risk factors, warrants caution until more research clarifies the picture.
The practical takeaway: sugar alcohols aren’t a single category you can label good or bad. Xylitol in your toothpaste is genuinely helpful. A sorbitol-sweetened protein bar might upset your stomach. Erythritol in your daily coffee sweetener might deserve a second look. Reading ingredient labels to know which sugar alcohol you’re actually consuming gives you much more useful information than treating them all the same.