Sugar Alcohols (Polyols): Sorbitol, Xylitol, Erythritol and Maltitol Explained

Sugar alcohols, also called polyols, are carbohydrates that taste sweet but are absorbed slowly or incompletely, so they supply less energy than sugar and raise blood glucose less. Sorbitol, xylitol, maltitol and erythritol are the ones you will meet most often. FSSAI's labelling regulations count polyols at 2 kcal per gram, against 4 kcal for sugar, and erythritol at 0. The cost is in the gut: beyond a certain dose most of them cause gas and loose stools. This entry is part of the carbohydrates section of the handbook.

What are sugar alcohols?

They are neither sugar nor alcohol in the everyday sense. A 2003 review in Nutrition Research Reviews describes polyols as hydrogenated carbohydrates used as sugar replacers, and none of them contains the ethanol found in drinks. Sorbitol and mannitol occur naturally in many fruits, and dried fruit such as prunes holds enough sorbitol to loosen the bowels. The polyols in packaged food are manufactured: maltitol from maltose, erythritol by fermentation.

The WHO keeps them apart from sweeteners such as sucralose and aspartame. Its 2023 guideline on non-sugar sweeteners says the advice does not apply to sugar alcohols, because they are sugars or sugar derivatives that contain calories. Those intense sweeteners are covered in NNWA's article on whether sugar-free sweeteners are safe.

Sorbitol, xylitol, erythritol and maltitol compared

The four differ mainly in how much is absorbed. Erythritol is the outlier: the European Food Safety Authority reports that 78 to 92 per cent of a dose is absorbed and passed unchanged in the urine within 24 hours, which is why it carries no energy and rarely reaches the large intestine. Xylitol is absorbed in part, about 90 per cent of a 5 g dose but 66 per cent of a 30 g dose in one study of adult men. Sorbitol is absorbed very slowly, and maltitol is split in the gut into glucose and sorbitol.

Treat the last column as a guide. The review that compiled it warns that such values are not universally valid: the result changes with body weight, with whether the polyol is taken in a drink or with solid food, and with habit.

How many calories do polyols carry on an Indian label?

Two per gram, by regulation. The Food Safety and Standards (Labelling and Display) Regulations, 2020, tell manufacturers to calculate energy with fixed factors: 4 kcal per gram for carbohydrates, 2 kcal for polyols except erythritol, 0 kcal for erythritol, 4 for protein and 9 for fat. A sweet in which 30 g of sugar has been replaced by 30 g of maltitol is therefore credited with 60 kcal from the sweetener where sugar would have given 120.

That is why a sugar-free sweet is seldom a low-calorie one. ICMR-NIN's Dietary Guidelines for Indians, 2024, makes the same point about the claim itself: sugar-free foods may be loaded with fats and refined cereals, and may hold what it calls hidden sugars, naming maltitol among them. The Indian food calorie counter gives the ordinary version of most sweets for comparison, and the page on kaju katli calories works one example through.

What must an Indian label say about polyols?

It must carry a laxative statement once polyols make up a tenth of the product. Schedule II of FSSAI's labelling regulations lists the mandatory declarations, each to be printed in a rectangular box. Sorbitol has a longer statement of its own, in force since 10 September 2021. Polyols sold as table-top sweeteners carry the same statements.

Two limits of this rule are worth knowing. A product with less than 10 per cent polyols needs no statement, so several such foods in a day can add up unannounced. And the statement names no quantity, so it cannot tell you how many pieces are too many.

Is there an Indian requirement or daily limit for polyols?

There is neither. Polyols are not nutrients the body needs, and ICMR-NIN's Nutrient Requirements for Indians, 2020, sets no requirement and no upper limit for them. FSSAI's labelling regulations set a warning, not a daily amount. The nearest thing to a numerical limit comes from Europe, where the food safety authority in 2023 set an acceptable daily intake for erythritol of 0.5 g per kg of body weight, chosen to protect against diarrhoea.

How much is too much for the gut?

For sorbitol, less than most people guess. A 2016 review of feeding studies reports that sorbitol and mannitol can change bowel habit in adults at 10 to 20 g a day, and that most experts expect osmotic diarrhoea from sorbitol somewhere between 20 g and 50 g. Xylitol is better tolerated, with the largest safe daily amounts ranging widely from 20 g to 70 g. Erythritol does not normally cause gut symptoms at all. Unabsorbed polyol draws water into the bowel and is fermented by bacteria.

Maltitol, the usual bulk sweetener in sugar-free chocolate and mithai, sits in between. In the studies that review summarises, 30 g in chocolate caused no significant symptoms in young adults, 40 g caused rumbling and wind without laxation, and a single 45 g dose brought on short-lived diarrhoea in 29 of 34 people. Children reach these doses sooner because they weigh less; the review describes a three-year-old who ate about 40 g of sorbitol as chewing gum and had cramps and watery diarrhoea within the hour.

Do sugar alcohols raise blood glucose?

Less than sugar, but not all of them equally. The 2003 review pooled the published glucose and insulin responses and gave glycaemic index values of 0 for erythritol, 9 for sorbitol, 13 for xylitol and 35 for maltitol, against 65 for sucrose and 100 for glucose. The matching insulin values were 2, 11, 11 and 27, against 43 for sucrose. The same values held in people with and without diabetes at intakes up to 50 g.

So maltitol behaves like a slower sugar, not like a zero. A person with diabetes still has to count a maltitol sweet, along with the flour, milk solids and fat that come with it. The article on sugar-free sweets for people with diabetes goes through the festive options, and the diabetes nutrition course teaches how sweeteners fit into a day's carbohydrate. The entry on added sugar gives the limits for sugar itself.

What does the dental evidence show?

That polyols do not feed decay is accepted; that xylitol actively prevents it is less certain than the packaging suggests. A Cochrane review in 2015 found 10 trials with 5,903 participants, seven of them at high risk of bias. Its main finding was that a fluoride toothpaste containing 10 per cent xylitol may reduce caries in children by 13 per cent over 2.5 to 3 years compared with a fluoride-only toothpaste, on low-quality evidence from 4,216 children in two studies by the same authors.

For xylitol lozenges, tablets, wipes and syrups the review judged the evidence insufficient, with results in most comparisons compatible with both less and more decay. A sugar-free gum or sweet spares the teeth the sugar it replaces; a preventive effect of xylitol itself is still unproven.

What did the 2023 erythritol study find?

It found an association, not proof of harm. Researchers at the Cleveland Clinic measured fasting blood erythritol in people having elective heart assessments. In a United States cohort of 2,149 and a European cohort of 833, those in the highest quarter of blood erythritol had about twice the risk of death, heart attack or stroke over three years compared with the lowest quarter, with adjusted hazard ratios of 1.80 and 2.21. In eight healthy volunteers, a drink with 30 g of erythritol kept blood levels raised for more than two days.

The limits are stated in the paper itself. Blood erythritol was measured once. The participants came from specialist heart centres and already had a high burden of cardiovascular disease, so the result may not carry over to the general population. The design can show association and not causation, and diet was not measured. The body also makes its own erythritol, and the authors think the fasting levels in the United States samples probably reflect that internal production.

The European Food Safety Authority reviewed the study in 2023 and concluded that the available evidence does not demonstrate a causal link between erythritol eaten as an additive and cardiovascular disease, adding that blood erythritol may be a marker of metabolic disturbance. The same research group has since reported that 30 g of erythritol increased measures of platelet reactivity in ten healthy volunteers, and a similar association for xylitol. No trial has yet tested whether eating erythritol changes the rate of heart attacks or strokes.

A worked example: one box of sugar-free sweets

This case and its label are invented to show the arithmetic. A 46-year-old schoolteacher in Pune who weighs 58 kg and has type 2 diabetes buys sugar-free sweets for Diwali. The label declares 30 g of maltitol per 100 g. Three pieces, 60 g in all, give her 18 g of maltitol: under the 30 g that caused no significant symptoms in the chocolate study, and credited with 36 kcal where 18 g of sugar would count as 72. The saving is 36 kcal, and with a glycaemic index of 35 the sweet still has to be counted.

Now suppose the sweetener were sorbitol. Using the review's figure for women, 0.24 g per kg, her largest single dose without laxation would be about 13.9 g, so the same 18 g would be past it. For xylitol the figure is 0.3 g per kg, or 17.4 g. For erythritol it is 0.80 g per kg, or 46.4 g in one go, while the European acceptable daily intake of 0.5 g per kg works out to 29 g across her day.

Common mistakes and myths about sugar-free foods

The commonest mistake is reading sugar free as permission to eat more, which cancels the small saving and invites the laxative effect. The second is assuming every polyol behaves alike, when maltitol has more than a third of the glycaemic effect of glucose and erythritol has none. The third is overlooking the polyols in foods not sold as sweets, a point the article on protein bars takes up.

A further mistake is treating the erythritol finding as either settled or dismissed. It is an open question, and moderation is a reasonable response to an open question about a sweetener that nobody needs to eat.

Who should be cautious, and when should you see a doctor?

Polyols are permitted food ingredients, and the 2016 review notes that the osmotic diarrhoea they cause is a response to unabsorbed carbohydrate in the bowel, not a disease. Some groups have less room for error, though, and diarrhoea that continues after you stop the product needs a medical opinion.

If your gut is sensitive, the low-FODMAP diet entry explains where polyols sit among the other fermentable carbohydrates. No polyol replaces a medicine, and none should be given to a child as a remedy for constipation without a doctor's advice.

Learning this subject at NNWA

Label reading and the place of sweetening agents in a diet are taught at NNWA, a private skill academy in Kolkata that teaches online in English and Hindi. Its programmes, which begin with the Certification in Nutrition, prepare learners to guide healthy clients and to send anyone with a medical condition to a doctor. No NNWA course is a degree or a dietitian qualification.