Sugar alcohols and your gut: what the research says

Sugar-free. No added sugar. Keto-friendly. Only 2 g net carbs. Those phrases often lead to the same place on the ingredient list: a sugar alcohol.

Sugar alcohols, also called polyols, sweeten foods with fewer calories and less effect on blood sugar. They're also a well-known cause of gas, bloating and loose stools. Here's what the studies actually found, and how to use that when you read a label.

How to spot them

Most sugar alcohols end in "-itol." Look for these names in ingredient lists:

• Sorbitol and mannitol
• Xylitol
• Maltitol, including maltitol syrup
• Lactitol
• Erythritol
• Isomalt and hydrogenated starch hydrolysates, the two that don't end in "-itol"

Some Nutrition Facts labels also show a "Sugar alcohol" line in grams. Keep in mind that "net carbs" isn't a term the FDA defines. It usually means sugar alcohols and fiber were subtracted from the total, which says nothing about how your gut will handle them.

Why they cause symptoms

Sugar alcohols are only partly absorbed in the small intestine. What isn't absorbed travels to the colon, where gut bacteria ferment it and produce gas. It can also draw water into the bowel.

A systematic review of 79 studies found that polyol malabsorption in healthy people generally depends on the dose, and that it increases when different polyols are eaten together. Polyols caused dose-dependent gas, abdominal discomfort and laxative effects in both healthy volunteers and people with IBS (Lenhart and Chey, 2017). Polyols are also the "P" in FODMAP, the group of fermentable carbs that a low-FODMAP diet limits.

Not all sugar alcohols behave the same

Erythritol versus xylitol. In a randomized, double-blind study, 64 healthy young adults drank single doses of xylitol or erythritol in water. At 50 g, xylitol increased nausea, bloating, rumbling, cramping and watery stools compared with sugar, and 35 g of xylitol already increased watery bowel movements. Erythritol at 20 g and 35 g didn't cause a significant increase in symptoms, and 50 g increased only nausea and rumbling (Storey et al., 2007).

Maltitol, isomalt and lactitol. In a crossover study, 59 healthy volunteers ate 100 g of milk chocolate made with 40 g of different sweeteners. Lactitol caused the most symptoms. Isomalt increased all symptoms, though none were rated severe. Maltitol caused less intolerance than isomalt, mainly mild gas, rumbling and cramping, and no laxative effect. For all three, symptoms depended on the dose (Koutsou et al., 1996).

These were deliberately large test doses in young, healthy people. They're useful for comparing sweeteners, not for predicting exactly how much you can tolerate.

A sensitive gut may react to less

One study gave 10 g of sorbitol or mannitol to 21 healthy people and 20 people with IBS. Overall digestive symptoms increased significantly after both polyols only in the IBS group, and those symptoms didn't depend on how well the sugar alcohols were absorbed. The same team measured food content and found sorbitol in certain fruits and in sugar-free gum (Yao et al., 2014).

So if your gut is already reactive, a modest amount spread across gum, mints and a low-sugar snack could be enough to notice.

A note on erythritol and heart health

In 2023, researchers reported that higher blood levels of erythritol were linked with a greater three-year risk of heart attack, stroke or death in people undergoing heart evaluations. In validation groups of 2,149 US and 833 European patients, those in the top quarter of erythritol levels had a higher risk than those in the bottom quarter. In a small pilot, eating erythritol raised blood levels in 8 healthy volunteers for more than two days (Witkowski et al., 2023).

This kind of study shows an association, not proof that erythritol causes heart problems. The authors called for studies of its long-term safety. For now, it's reasonable not to treat any sweetener as something to eat in unlimited amounts.

What to do with this at the store

1. Scan ingredient lists for "-itol" names and isomalt, especially on anything labeled sugar-free or keto.
2. Count your sources across a day: gum, mints, bars, gummies and "no sugar added" desserts.
3. If you bloat easily, remove them for two weeks and track your symptoms, then add one product back.
4. Because the effects depend on dose, keep portions small rather than having several sugar-free products at once.

When to see a doctor

If loose stools or bloating continue after you've cut out sugar alcohols, or you notice blood in your stool, weight loss you can't explain or symptoms that wake you at night, see your doctor. Those aren't sweetener problems.

Sources

1. Lenhart A, Chey WD. A systematic review of the effects of polyols on gastrointestinal health and irritable bowel syndrome. Adv Nutr. 2017;8(4):587-596. PMID 28710145
2. 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
3. Koutsou GA, Storey DM, Lee A, et al. Dose-related gastrointestinal response to the ingestion of either isomalt, lactitol or maltitol in milk chocolate. Eur J Clin Nutr. 1996;50(1):17-21. PMID 8617186
4. 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
5. Witkowski M, Nemet I, Alamri H, et al. The artificial sweetener erythritol and cardiovascular event risk. Nat Med. 2023;29(3):710-718. PMID 36849732

This article is for general information and isn't medical advice. If you have IBS, diabetes or heart disease, talk to your healthcare provider or a registered dietitian about which sweeteners suit you.