Sugar Alcohols (Polyols)

Sugar alcohols (polyols) are sweeteners that sit chemically between sugars and alcohols. They taste sweet but are absorbed poorly in the small intestine. The unabsorbed portion reaches the colon, where bacteria ferment it and the osmotic load pulls water in — producing gas, bloating, cramping, and loose stools. They're the most common cause of acute digestive distress from "sugar-free" products.

Common ones: sorbitol, mannitol, xylitol, maltitol, isomalt, lactitol, and erythritol. They're used in sugar-free gum, mints, candy, "low-carb" snacks and ice cream, protein bars, toothpaste, and some medications. They also occur naturally in some fruits — sorbitol in apples, pears, plums, prunes; mannitol in mushrooms and cauliflower.

Why they cause GI symptoms

Tolerance is dose-dependent. A few sticks of sugar-free gum can deliver 10–20g of polyols and reliably trigger bloating in many people; a single after-dinner mint usually doesn't. The FDA requires a warning on products containing 50g+ of sorbitol per serving — but most people react well below that threshold. Polyols are also one of the categories restricted in low-FODMAP diets; people with IBS are usually substantially more sensitive than the general population.

Tolerance varies by polyol

Erythritol is the best-absorbed and least likely to cause symptoms at moderate doses — most people tolerate it well, though there's recent emerging research on possible cardiovascular signals at very high intakes. Maltitol and sorbitol are the worst-tolerated. Xylitol is somewhere in between for humans but is severely toxic to dogs — even small amounts can cause life-threatening hypoglycemia, so xylitol products must be kept away from pets.