Sugar alcohols and bloating: which ones are gentler?

Check the back of a sugar-free gum pack, a keto snack bar or a "no sugar added" chocolate and you'll often find ingredients ending in "-itol." These are sugar alcohols, also called polyols, and they add sweetness without regular sugar. Some of them are also well-known gas and bloating triggers.

They're not all the same, though. Here's how the common ones compare in controlled studies, and how to test them for yourself.

Why sugar alcohols can cause gas

Many sugar alcohols aren't fully absorbed in the small intestine. What isn't absorbed travels on to the colon, where it can draw in water and be fermented by bacteria. A review of the research notes that many polyols can cause digestive symptoms, at least in people who aren't used to them, and that how well each is tolerated depends partly on its molecular size and structure (Mäkinen, 2016).

The same review notes that some adaptation may happen with regular use as gut bacteria adjust (Mäkinen, 2016). As you'll see below, though, that didn't show up for every polyol that was tested.

How the common ones compare

Sorbitol: among the least forgiving. In a classic study, 7 healthy volunteers took 5, 10 and 20 grams of sorbitol. As little as 5 grams raised breath hydrogen in most of them, a sign it wasn't fully absorbed. Most had mild gas and bloating after 10 grams, and severe symptoms such as cramps and diarrhea after 20 grams (Hyams, 1983). Sorbitol occurs naturally in certain fruits and is used in sugar-free gum (Yao et al., 2014).

Mannitol: a close relative, found in some vegetables. In a double-blind study of 21 healthy people and 20 people with irritable bowel syndrome (IBS), 10 grams of sorbitol or mannitol increased digestive symptoms only in the IBS group. Only 33% of the healthy participants and 40% of those with IBS fully absorbed the sorbitol dose (Yao et al., 2014).

Xylitol: better tolerated, but dose matters. In a double-blind trial, 64 young adults took single doses of xylitol or erythritol dissolved in water. Compared with 45 grams of table sugar, 50 grams of xylitol increased bloating, nausea, rumbling, cramping and watery stools, and 35 grams increased watery stools (Storey et al., 2007). The review describes xylitol as better tolerated than sorbitol, mannitol or maltitol (Mäkinen, 2016).

Erythritol: the gentlest in these studies. In the same trial, 20 and 35 grams of erythritol caused no significant increase in symptoms. At 50 grams, only nausea and rumbling increased (Storey et al., 2007). Erythritol is a smaller molecule and normally avoids the digestive reactions seen with other polyols (Mäkinen, 2016).

Maltitol: tolerated by healthy volunteers until the dose climbs. In a double-blind crossover study, 12 healthy volunteers ate increasing daily amounts of maltitol or sugar until diarrhea or a severe symptom appeared. That threshold averaged about 92 to 93 grams a day for maltitol, compared with 106 to 113 grams for sugar. Diarrhea was more common with maltitol, and 9 days of regular use didn't raise the threshold (Ruskoné-Fourmestraux et al., 2003).

The comparison at a glance

• Most likely to cause gas and bloating at modest doses: sorbitol and mannitol, especially in people with IBS
• Middle of the pack: maltitol and xylitol, with symptoms rising at higher doses
• Least likely to cause symptoms in these studies: erythritol

What these studies don't tell you

Most of this research used single doses dissolved in water, often in healthy young adults. Real foods contain fiber, fat and other ingredients that may change how a polyol behaves, and a sensitive gut can react to amounts that don't bother others, as the IBS findings show (Yao et al., 2014).

The amount in a single serving varies widely from product to product. Polyols can also add up across a day of sugar-free gum, mints, bars and drinks, which is easy to miss if you only look at one label at a time.

Where they tend to turn up

Sugar alcohols aren't limited to obvious diet foods. Places worth checking include:

• Sugar-free gum, mints and hard candies
• Protein bars, keto bars and "low net carb" snacks
• Sugar-free chocolate, ice cream and baked goods
• Sugar-free syrups and drink mixes
• Some chewable or gummy supplements

How to spot them on a label

• Sorbitol, mannitol, xylitol, erythritol, maltitol, isomalt and lactitol
• "Hydrogenated starch hydrolysate" or "maltitol syrup"
• A "Sugar Alcohol" line under Total Carbohydrate on the Nutrition Facts panel, which some products include
• Front-of-pack wording like "sugar-free," "no sugar added" or "keto," which is a good reason to read the ingredient list

A simple two-week test

1. For two weeks, avoid products that contain any of the ingredients above.
2. Rate your bloating from 0 to 10 at the same time each afternoon.
3. Reintroduce one sweetener at a time, in a normal serving, for a few days.
4. Note the amount and your symptoms. You may find you're fine with erythritol but not sorbitol, or with one serving but not three.

If persistent diarrhea, blood in your stool, weight loss or symptoms at night continue after cutting out sugar alcohols, see a doctor. Those need a medical check regardless of what you eat.

Sources

1. Mäkinen KK. 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. Int J Dent. 2016;2016:5967907. PMID 27840639
2. Hyams JS. Sorbitol intolerance: an unappreciated cause of functional gastrointestinal complaints. Gastroenterology. 1983;84(1):30-3. PMID 6847853
3. Yao CK, Tan HL, van Langenberg DR, et al. Dietary sorbitol and mannitol: food content and distinct absorption patterns between healthy individuals and patients with irritable bowel syndrome. J Hum Nutr Diet. 2014;27 Suppl 2:263-75. PMID 23909813
4. Storey D, Lee A, Bornet F, Brouns F. Gastrointestinal tolerance of erythritol and xylitol ingested in a liquid. Eur J Clin Nutr. 2007;61(3):349-54. PMID 16988647
5. Ruskoné-Fourmestraux A, Attar A, Chassard D, Coffin B, Bornet F, Bouhnik Y. A digestive tolerance study of maltitol after occasional and regular consumption in healthy humans. Eur J Clin Nutr. 2003;57(1):26-30. PMID 12548293

This article is for general information and isn't medical advice. If you have ongoing digestive symptoms or a condition that affects how you use sweeteners, such as diabetes, talk to your healthcare provider or a registered dietitian.