Sugar alcohols, sometimes called alcohol sugars or polyols, are a class of sweeteners found in everything from sugar-free gum to protein bars. Despite the name, they contain no ethanol and will not get you drunk. They are carbohydrates whose chemical structure happens to resemble both a sugar and an alcohol, which is where the confusing label comes from. Common examples include xylitol, erythritol, sorbitol, maltitol, mannitol, lactitol, and isomalt, and each behaves a little differently in your body.
How Sugar Alcohols Differ from Regular Sugar
Table sugar is fully absorbed in your small intestine and delivers about four calories per gram. Sugar alcohols follow a different path. Because their molecular structure is altered, your small intestine absorbs them only partially. A study that tracked absorption in healthy volunteers found that roughly 79% of sorbitol was absorbed in the small intestine, while about 90% of maltitol was digested, and whatever reached the colon was fermented by gut bacteria rather than excreted.1PubMed. Digestion and absorption in the human intestine of three sugar alcohols That partial absorption is why sugar alcohols deliver fewer usable calories than table sugar. The same study estimated energy values of roughly 3.1 to 3.6 calories per gram for the sugar alcohols tested, compared with the full four calories per gram you get from regular sugar.2PubMed. Digestion and absorption in the human intestine of three sugar alcohols
Erythritol is the outlier. About 90% of it gets absorbed in the small intestine and then excreted unchanged in urine, meaning it contributes almost no calories. That makes it the lowest-calorie option in the group, typically listed at around 0.2 calories per gram. Maltitol, by contrast, sits at the higher end, delivering close to three calories per gram and raising blood sugar more noticeably than the others. If you are reading labels on “sugar-free” products, knowing which sugar alcohol is being used matters more than the blanket category.
Why They Can Upset Your Stomach
The signature side effect of sugar alcohols is gastrointestinal distress, and the reason is straightforward. The portion that is not absorbed in the small intestine moves into the colon, where it draws water into the gut by osmosis and gets fermented by bacteria. The result is bloating, gas, cramping, and, if you eat enough, diarrhea. Research in animal models has confirmed that the intestinal malabsorption of sorbitol is the primary driver of osmotic diarrhea.3PubMed Central. Sorbitol-based osmotic diarrhea: possible causes and mechanism of prevention investigated in rats
The good news is that this is a nuisance, not a danger. A scientific review of gastrointestinal disturbances from sugar alcohols found no pathology associated with polyol-induced osmotic diarrhea, meaning the intestinal lining retains its normal structure even during episodes, except in extreme cases.4PubMed Central. Gastrointestinal Disturbances Associated with the Consumption of Sugar Alcohols with Special Consideration of Xylitol: Scientific Review and Instructions for Dentists and Other Health-Care Professionals Your gut also adapts over time: people who consume sugar alcohols regularly tend to tolerate higher amounts before symptoms kick in. This is partly because colonic bacteria shift their populations to better handle the incoming polyols.
Tolerance thresholds vary by type. Erythritol is the best tolerated because so little of it reaches the colon. Most people can handle 50 grams or more per day without symptoms. Sorbitol and maltitol cause problems at much lower doses, sometimes as little as 10 to 20 grams. For context, a single sugar-free candy bar can contain 15 to 20 grams of maltitol, which explains why some products carry the now-infamous warning label about “excessive consumption” and a “laxative effect.”
Effects on Blood Sugar
This is usually why people reach for sugar alcohols in the first place. Because they are only partially absorbed and metabolized through pathways that require less insulin, most sugar alcohols produce a much smaller rise in blood glucose than table sugar or pure glucose. A review of sugar alcohols as antidiabetic supplements concluded that polyols like xylitol, sorbitol, erythritol, and others are appropriate sugar substitutes for diabetic diets because some of them do not raise plasma glucose at all.5PubMed Central. Suitability of sugar alcohols as antidiabetic supplements: A review
Erythritol stands out here again. Because it is absorbed and excreted without being metabolized for energy, it has essentially no effect on blood glucose or insulin. Xylitol causes only a slight bump. Maltitol, however, has a glycemic index of around 35 to 52, depending on the form. That is lower than table sugar’s glycemic index of 65, but it is hardly negligible, and people with diabetes who eat maltitol-heavy products thinking they are “sugar-free” can be caught off guard by a meaningful blood sugar spike.
A clinical trial compared a sugar-alcohol mixture called lacritose against glucose and sucrose in both healthy subjects and people with type 2 diabetes. Blood glucose was significantly lower at every time point after ingesting the sugar-alcohol blend compared with glucose or sucrose in the diabetic group, and was also lower at 30 and 60 minutes in the healthy group.6Endocrinología, Diabetes y Nutrición (English ed.). The effect of a new mixture of sugar and sugar-alcohols compared to sucrose and glucose on blood glucose increase and the possible adverse reactions Gastrointestinal side effects in that trial were not significantly different between the test beverages, suggesting that formulated blends can avoid the gut issues sometimes seen with pure polyols.
The Dental Advantage
If sugar alcohols have one unambiguous health benefit, it is for your teeth. Cavity-causing bacteria, especially Streptococcus mutans, thrive on regular sugar. They ferment it into acids that eat away at tooth enamel. Sugar alcohols are poor fuel for these bacteria, so switching from sugar to a polyol sweetener starves them. Xylitol goes a step further. It is actively taken up by S. mutans but cannot be metabolized, which disrupts the bacteria’s energy cycle and can reduce their population in your mouth over time.
A randomized, double-blind crossover trial compared xylitol chewing gum against sorbitol chewing gum. S. mutans and S. sobrinus counts dropped significantly in the xylitol group but not in the sorbitol group, supporting the idea that xylitol has a targeted antimicrobial effect that other sugar alcohols lack.7PubMed Central. Effect of xylitol on cariogenic and beneficial oral streptococci: a randomized, double-blind crossover trial A systematic review echoed this, noting that xylitol reduces levels of mutans streptococci in both plaque and saliva.8PubMed Central. Xylitol in preventing dental caries: A systematic review and meta-analyses
Habitual xylitol use has been linked to significant reductions in cavity incidence and even some degree of remineralization of existing lesions. Erythritol may share some of this benefit, with literature suggesting it can also lower caries incidence.9PubMed Central. Sugar alcohols, caries incidence, and remineralization of caries lesions: a literature review However, the mechanism behind any remineralization appears to be indirect. When polyols were added to artificial saliva solutions, they did not improve remineralization of enamel lesions beyond what the saliva solution achieved on its own.10PubMed. Polyols and remineralisation of enamel subsurface lesions In other words, the dental benefit is mainly defensive: sugar alcohols protect your teeth by not feeding the bacteria that cause damage, rather than by actively rebuilding enamel.
One study on chewing gums did find that all gum groups, including a paraffin control, showed increased enamel microhardness after chewing periods, likely because chewing itself stimulates saliva flow, which naturally promotes remineralization.11PubMed Central. Effect of chewing gums with xylitol, sorbitol and xylitol-sorbitol on the remineralization and hardness of initial enamel lesions in situ So when you see xylitol gum marketed for “rebuilding enamel,” the chewing itself deserves some of the credit.
Emerging Cardiovascular Concerns
This is where the picture gets complicated and genuinely unsettled. In 2023 and 2024, two high-profile studies raised alarms about erythritol and xylitol, the two sugar alcohols most popular in “keto” and low-carb products.
Research published in a major cardiovascular journal reported that fasting plasma levels of erythritol are clinically associated with heightened cardiovascular disease risk and that erythritol can enhance thrombosis potential, meaning it may make blood platelets stickier and more prone to clotting.12PubMed Central. Ingestion of the Non-Nutritive Sweetener Erythritol, but Not Glucose, Enhances Platelet Reactivity and Thrombosis Potential in Healthy Volunteers-Brief Report A separate study found a similar pattern for xylitol, reporting that people in the highest third of plasma xylitol levels had roughly 57% higher risk of major adverse cardiovascular events compared with those in the lowest third.13European Heart Journal. Xylitol is prothrombotic and associated with cardiovascular risk
A commentary in Cardiovascular Research acknowledged these findings while urging caution about drawing firm conclusions. The authors noted that higher fasting plasma concentrations of erythritol and xylitol are associated with increased cardiovascular risk and might predict major adverse cardiovascular events, but the research so far does not definitively establish that eating erythritol or xylitol in food causes heart problems.14Cardiovascular Research. Sweeteners: erythritol, xylitol and cardiovascular risk—friend or foe? A key issue is that your body produces erythritol and xylitol internally through the polyol pathway, and people with metabolic syndrome or diabetes tend to have elevated endogenous production of these compounds. So the association between high blood levels and cardiovascular events might reflect underlying metabolic disease rather than anything caused by dietary intake.
The evidence is early-stage and vigorously debated. If you are someone with existing heart disease or major cardiovascular risk factors who also consumes large daily amounts of erythritol or xylitol, it is reasonable to pay attention as more data arrive. For people without those risk factors eating moderate amounts, the findings do not yet warrant alarm, but they are a reminder that “natural” or “sugar-free” labels are not automatic safety guarantees.
What Sugar Alcohols Do to Appetite and Gut Hormones
You might expect that a sweetener with few or no calories would leave your body unsatisfied, but erythritol and xylitol appear to trigger real physiological satiety signals. A study in both lean and obese subjects found that erythritol and xylitol led to marked increases in CCK and GLP-1, two gut hormones that signal fullness, while also significantly slowing gastric emptying, meaning food stays in your stomach longer.15PubMed. Gut hormone secretion, gastric emptying, and glycemic responses to erythritol and xylitol in lean and obese subjects Erythritol did all of this without affecting insulin or plasma glucose at all. Xylitol produced a slight insulin bump, but it was minor.
A follow-up dose-ranging study on erythritol alone confirmed the pattern in a dose-dependent way: higher doses of erythritol triggered more CCK, GLP-1, and PYY (another satiety hormone) release, and further slowed gastric emptying. Blood glucose, insulin, lipids, and uric acid were all unaffected, and no one reported abdominal pain, nausea, or vomiting.16PubMed Central. Gastric emptying of solutions containing the natural sweetener erythritol and effects on gut hormone secretion in humans: A pilot dose‐ranging study
The catch is that despite these hormonal signals, the studies did not find that subjective feelings of appetite were significantly different after consuming sugar alcohols compared with a placebo.17PubMed. Gut hormone secretion, gastric emptying, and glycemic responses to erythritol and xylitol in lean and obese subjects So your gut sends “I’m full” signals to your brain, but whether that meaningfully reduces how much you eat at the next meal remains unclear. Anyone hoping that switching to erythritol-sweetened snacks will automatically lead to weight loss should temper expectations. The calorie savings are real, but the appetite-suppression story is not yet convincing in practice.
Sugar Alcohols and Your Gut Microbiome
Beyond causing gas and bloating, the unabsorbed portion of sugar alcohols that reaches your colon serves as food for gut bacteria, and the effects are not all bad. A review of allulose and sugar alcohols found that they can act as prebiotics, fostering the growth of beneficial bacteria and stimulating the production of short-chain fatty acids, which are linked to reduced inflammation and improved gut-barrier function.18Universal Journal of Pharmaceutical Research. THE ROLE OF ALLULOSE AND SUGAR ALCOHOLS IN GUT MICROBIOTA MODULATION AND METABOLIC HEALTH: A REVIEW This is the same mechanism by which foods like garlic, onions, and whole grains are considered prebiotic, and it partly explains why regular consumers adapt and experience fewer GI symptoms over time. Their colonic bacteria have shifted to better handle the incoming polyols, producing useful metabolites rather than excessive gas.
That said, the prebiotic effect depends heavily on which sugar alcohol you are consuming and in what quantity. Erythritol, because so little of it reaches the colon, is unlikely to have meaningful prebiotic activity. Sorbitol and isomalt deliver more undigested material to colonic bacteria and are more likely to influence the microbiome, for better and worse.
Why Xylitol Is Dangerous for Dogs
This is one of the most important practical things to know about sugar alcohols. Xylitol is safe for humans but can be lethal to dogs. In dogs, xylitol triggers a massive insulin release that causes rapid and severe hypoglycemia, and this response is far stronger than what occurs in humans. A study on experimental xylitol toxicity in dogs found that plasma insulin concentrations rose sharply within 20 minutes of dosing, peaked at 40 minutes, and were followed by a dangerous drop in blood glucose starting at 30 minutes.19PubMed. Experimental acute toxicity of xylitol in dogs Beyond hypoglycemia, xylitol ingestion caused elevated liver enzymes and electrolyte disturbances.
A veterinary review confirmed that acute death from severe hypoglycemia is possible if untreated, and liver failure can develop one to three days after ingestion.20Veterinary Clinics: Small Animal Practice. Xylitol Toxicity in Dogs Even small amounts are dangerous. A few sticks of xylitol-sweetened gum can be enough to send a small dog into crisis. If you keep sugar-free products in your home and have a dog, store them as carefully as you would chocolate or medication. Many peanut butter brands have started adding xylitol as a sweetener, which is a particularly insidious risk because peanut butter is a common treat for dogs.
Your Body Makes Its Own Sugar Alcohols
Here is something most people do not realize: you do not need to eat sugar alcohols to have them circulating in your body. Your liver produces sorbitol through what is called the polyol pathway, an internal process that converts glucose to sorbitol and then to fructose. Researchers have found elevated levels of both fructose and sorbitol in the livers of mice fed high-glucose diets, along with increased expression of the enzymes that drive this pathway.21Nature Communications. Endogenous fructose production and metabolism in the liver contributes to the development of metabolic syndrome The same research showed that this endogenous sorbitol-to-fructose conversion contributes to the development of fatty liver and metabolic syndrome, because the fructose produced internally has the same harmful metabolic effects as fructose consumed in food.
Uric acid, which is elevated in conditions like gout and metabolic syndrome, appears to ramp up this pathway further. In human liver cells, exposure to high uric acid levels caused a dose-dependent increase in aldose reductase, the enzyme that kicks off sorbitol production, with a nearly fourfold increase at the highest concentrations tested.22Journal of Biological Chemistry. Uric acid induces hepatic steatosis by generating endogenous fructose production via the activation of aldose reductase This creates a feedback loop: metabolic dysfunction increases internal sugar alcohol production, which generates more fructose, which worsens metabolic dysfunction.
This internal chemistry also complicates the cardiovascular findings discussed earlier. When researchers see high blood levels of erythritol or xylitol associated with heart disease, they cannot easily separate how much came from dietary intake and how much the body produced on its own in response to metabolic stress. It is a genuine methodological challenge that will take years of further research to untangle.
Choosing Between Sugar Alcohols
Not all sugar alcohols are interchangeable, and picking the right one depends on what you care about most. Here is how the major players stack up on the dimensions that matter to most consumers:
- Erythritol: Near-zero calories, no blood sugar impact, best GI tolerance at typical doses, but now under scrutiny for potential cardiovascular effects at high intake levels.
- Xylitol: About 2.4 calories per gram, minimal blood sugar impact, strong dental benefits, triggers satiety hormones, but deadly to dogs and also flagged in cardiovascular research.
- Sorbitol: About 2.6 calories per gram, moderate blood sugar effect, commonly used in candies and medications, relatively low GI tolerance threshold.
- Maltitol: About 2.1 to 3 calories per gram, highest glycemic index of the common sugar alcohols, tastes the most like sugar, most likely to cause unexpected blood sugar spikes in diabetics.
- Isomalt: About 2 calories per gram, low glycemic impact, popular in hard candies and baking because it resists crystallization, but can cause GI symptoms at moderate doses.
Product labels in the United States list sugar alcohols on the Nutrition Facts panel, but they are grouped under a single line rather than broken out by type. You have to check the ingredient list to see which specific polyol is used. In the European Union, sugar alcohols are assigned E-numbers (E420 for sorbitol, E967 for xylitol, E968 for erythritol, and so on), and any product containing more than 10% added polyols must carry an advisory that “excessive consumption may produce laxative effects.” No equivalent mandatory warning exists in the United States, though many manufacturers include one voluntarily.
For baking at home, erythritol and xylitol are the most commonly available retail options. Erythritol has a cooling sensation on the tongue that some people find pleasant in mints and beverages but odd in cookies. It also does not caramelize or brown the way sugar does, since it is excreted unchanged by the body and behaves similarly under heat. Xylitol, on the other hand, has a sweetness and mouthfeel close to table sugar and works well in most recipes, though you need to keep it away from pets. Maltitol-based syrups are widely used in commercial “sugar-free” chocolates because they mimic the texture and melting properties of sugar syrups, which is why sugar-free chocolate can taste surprisingly convincing while still delivering a decent number of calories and a noticeable glycemic response.