You probably haven’t heard of sugar alcohols before—they don’t garner the nutritional spotlight the way table sugar and artificial sweeteners do. But we can almost guarantee you've eaten them before.
Sugar alcohols occur naturally in certain fruits and vegetables: pears, apples, dried fruit, mushrooms, snow peas, avocados. But they can also be chemically processed and used as non-sugar sweeteners to boost the flavor of food and still score the label of “sugar-free,” says Danielle Capalino, R.D., author of Healthy Gut, Flat Stomach! In fact, most products labeled “sugar-free” likely have an artificial sugar alcohol compound in them.
Even their name is confusing: “Sugar alcohols are not actually a sugar (though they taste sweet) and not alcohol (like what you would find in beer), but rather a group of carbohydrates that partially resembles both sugar and alcohol, chemically,” explains Liz Applegate, Ph.D., director of sports nutrition at the University of California, Davis.
You’re probably familiar with a few types: sorbitol, mannitol, erythritol, maltitol. Each has varying degrees of side effects on your digestive system (we’ll get to those in a sec), but in general, they’re all more or less nutritionally the same, Applegate says.
The biggest question: Since sugar is the new enemy of the state, are sugar alcohols a healthier alternative?
Well, they’re certainly better for your teeth: Dentists like the compounds because sugar-free chewing gum doesn’t cause cavities the way regular gum does, Capalino points out.
Nutritionally, certain aspects of sugar alcohols make them healthier than alternatives. Sugar can actually damage your body by causing your insulin levels and blood sugar to spike, which inevitably comes with a crash in your energy levels. “These sugar alcohols give sweetness to food but do not raise insulin levels, because insulin isn’t needed for processing them,” Applegate says. This makes sugar alcohols ideal for diabetics, while also helping pre-diabetics control the fate they’re headed toward. In fact, some research even suggests that avoiding these insulin spikes may lower your risk for certain cancers, she adds.
The other main perk: “Sugar alcohols do not have calories, so they technically are ‘better for you’ because you get the sweetness without the calories of sugar,” says Capalino.
The reason they have fewer cals—less than 2 calories per gram compared to table sugar’s 4 cal/g—is that we can only partially digest the large molecules.
But this perk comes with a price: The undigested part of the compound remains in your digestive tract, so your intestinal bacteria ferments the molecules while your body also pulls in water to help pass the undigested molecules through, Applegate explains. The result of the whole process? Gas, bloating, and, potentially, even diarrhea.
This is actually the reason why running gels and protein bars sometimes give you GI distress. “Manufacturers put sugar alcohols in sports nutrition chews and drinks to give calories but avoid a rise in blood glucose and insulin levels,” Applegate says. That’s not always a smart move. You don’t really need blood sugar control during exercise, because your body leverages any kind of sugar for fuel so quickly that insulin isn’t even released.
The good news: Unabsorbed sugar alcohols will pass through your intestines and, other than the GI distress, won’t cause harm, Applegate says. But the digestive discomfort can be a real problem, especially for athletes, she adds. In addition to the stomach woes, during exercise your body shuttles blood to your muscles, giving your GI tract less support when it’s trying to digest something already more difficult than normal, she explains.
If you’re aiming for fewer calories or more control over your blood sugar, sugar alcohols can be a healthy addition to your diet—but you will likely have GI distress. Stick to fewer than 50g of sorbitol per day, and fewer than 20g per day of the others to minimize the discomfort, Applegate advises.
But even from a caloric standpoint, Capalino says she’s not a fan of sugar alcohols. “When you taste something sweet your body craves calories, and it will signal that it wants them somewhere else,” she explains. “I think you’re better off having small amounts of real sugar instead of thinking it’s okay to eat a lot of something because it is labeled ‘sugar free.’”