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Ask the RD

Question: I know what sugar is, and what alcohol is, but what are “sugar alcohols”?

Answer: Sugar alcohols—also known as polyols—include sorbitol, xylitol, erythritol, mannitol and isomalt. All the -ols, I like to say, plus isomalt. They taste sweet like sugar and have a cooling effect in the mouth. Chemically, polyols are carbohydrates, and they are not intoxicating like alcohol (Grembecka 2015). Unlike artificial sweeteners, including aspartame and saccharin, sugar alcohols naturally occur in fruit like plums and berries and in some vegetables.

You will see sugar alcohols on the ingredient lists of some candy and chocolate, gum, and other sweets, especially those labeled “sugar-free,” and in products marketed to people with diabetes. Because they contain fewer calories than sugar (2–3 calories per gram compared with 4 calories per gram for sugar), have a lower glycemic index than sugar, and add bulk to food more than artificial sweeteners do, sugar alcohols are widely used food additives (Grembecka 2015).

Polyols even have antibacterial properties, reducing the risk of cavities when used in gum. Xylitol has been studied as a preventive treatment for recurrent ear infections in children (Uhari et al. 1996). Sugar alcohols sound good, right? In small amounts, they are. But in larger amounts, they are associated with uncomfortable gastrointestinal symptoms like bloating, gas and diarrhea in some people. Polyols are not well digested in the small intestine, so they make it to the large intestine, where they pull water into the gut and are digested by bacteria that produce gas. Have you ever wondered why prunes are known for their laxative effect? Sugar alcohols, along with fiber, help explain it.

How much is too much when it comes to polyols? A dose of 50 g of xylitol may cause diarrhea (Storey et al. 2007), which is why some sugar-free candies come with warning labels. These gastrointestinal side effects are the reason the Academy of Nutrition and Dietetics suggests that people with irritable bowel syndrome (IBS) avoid sugar alcohols (AND 2012; AND 2014).

In fact, polyols are the P in FODMAPs, the acronym for substances people with gastrointestinal disorders may absorb poorly and should therefore avoid. Everyone is unique, but if you have IBS or frequent gastrointestinal symptoms, it’s worth paying attention to your intake of sugar alcohols.

Sanna Delmonico, MS, RDN, CHE, is on the faculty at The Culinary Institute of America at Greystone, in Napa, California, where she teaches food safety, nutrition and gastronomy. As a dietitian nutritionist working in a culinary school, she makes it her goal to help students see the connection between good health and delicious food.

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