If you look at the label on most sugar-free items, you‘ll see a curious ingredient: sugar alcohol (polyols), a nutrient that occurs naturally in fruits and vegetables and tastes almost as sweet as sugar relative to weight. While the name may sound ominous, sugar alcohol is a substitute for artificial sweeteners such as sucralose and aspertame. “Sugar alcohols can be metabolized into energy, but they don‘t trigger an insulin response because absorption of glucose and caloric sugars is slowed in their presence,” says Luke Bucci, PhD, vice president of research at Schiff Nutrition International. These alcohols also range in caloric content from 0-3 calories per gram, whereas regular sugars come in at 4 calories a gram. Because of this you may sometimes see the designation “net carbs” on a protein bar wrapper. The calculation works like this: total carbs – fiber – sugar alcohols = net carbs. This represents the actual amount of calorie-containing carbohydrates in a bar.

Consuming polyols in large quantities, however, can lead to gastrointestinal distress. “Sugar alcohols at higher intakes (more than 20-30 grams) feed gut bacteria and can produce gas. It all depends on what kind of critters are in your gut,” Bucci says. He adds that consuming more than 50 grams can pull water into the gut, causing loose stools or temporary diarrhea, and that they can stay in your system 12-24 hours. So be mindful of your total daily consumption.

But you don‘t have to avoid them. In fact, in addition to preventing protein bars from getting hard, Bucci says sugar alcohols (like xylitol) don‘t cause tooth decay like regular sugar because mouth germs don‘t like to use it for food. Perhaps most important, polyols have been extensively studied over decades because they are regularly used in diabetic foods and have a well-documented safety record.