Sugar alcohols aren’t sugar and they’re not alcohol. Most are made by adding hydrogen molecules to sugars. The added hydrogen makes it harder for them to be absorbed in the digestive tract, which means they deliver fewer calories. But reduced absorption has a downside: sugar alcohols can cause GI distress if you eat too much.
On the plus side, sugar alcohols (along with non-caloric sweeteners) don’t promote tooth decay. And they’re absorbed slowly and don’t cause blood sugar to increase rapidly, which makes them better than sugar for people with diabetes.
Erythritol: It’s 60 to 70 percent as sweet as sugar. Erythritol is unique among sugar alcohols. It has far fewer calories than the others (so little that a teaspoon has less than 1 calorie), and most of it is excreted unchanged in the urine. The other sugar alcohols end up in the large intestine, which can cause diarrhea and gas. However, eating more than about 50 grams of erythritol may cause nausea.
Xylitol, maltitol, sorbitol, mannitol, isomalt, lactitol: They vary from roughly as sweet as sugar (xylitol) to about a third as sweet (lactitol). (We’ve listed them in descending order of sweetness.)
Consuming even as little as 20 grams a day of some of these sugar alcohols may lead to bloating, gas, and diarrhea. (Sensitivities vary widely, though, and some people develop a tolerance to GI distress.)
The FDA requires foods “whose reasonably foreseeable consumption may result in a daily ingestion of 20 grams of mannitol” to carry this warning: “Excess consumption may have a laxative effect.” The same goes for foods that could lead someone to consume 50 grams of sorbitol in a day. Warnings aren’t required on foods that contain other sugar alcohols, but they should be.
Nutrition Facts labels don’t have to list the amount of sugar alcohols per serving unless the package makes a sugar or sugar alcohols claim (“Sugar Free,” for example).