Scientists have uncovered potential metabolic risks linked to sorbitol, a type of sugar alcohol used in sugar-free products like gum and candy. Researchers from Washington University in St. Louis discovered that the body can convert sorbitol into fructose in the liver, which could lead to harmful effects similar to those caused by consuming fructose. The study, published in Science Signaling, expands on earlier work by Gary Patti’s lab at the university, which has explored how fructose affects the liver and other organs. Sorbitol is often marketed as a healthier substitute for refined sugar, but recent research is challenging the idea that all sugar alternatives are automatically better for the body. The study suggests that sorbitol may not be as harmless as previously thought. It found that sorbitol isn’t just consumed through food—it can also be produced by enzymes in the intestine from glucose after a meal. This means that even people who don’t eat sorbitol directly could still be exposed to it. The body’s handling of sorbitol depends on factors like the amount of glucose and sorbitol consumed and the types of bacteria in the gut. These factors can influence how sorbitol is processed and whether it reaches the liver, where it may be converted into fructose-like compounds. While earlier studies on sorbitol often focused on conditions like diabetes—where high glucose levels can lead to increased sorbitol production—new research using zebrafish showed that significant sorbitol production can occur in the intestine without diabetes. Some gut bacteria play a key role in managing sorbitol. Certain strains of Aeromonas bacteria can break down sorbitol and turn it into harmless byproducts. This microbial process helps keep sorbitol from entering the bloodstream. However, if these bacteria aren’t present, sorbitol can move into the liver, where it may be converted into fructose-like compounds. This is particularly relevant for people with diabetes or other metabolic conditions who may choose sugar-free products to avoid the negative effects of regular sugar. The study highlights that while small amounts of sorbitol—like those found in fruit—can be safely processed by gut bacteria, larger amounts can overwhelm these microbes. This can happen in two main ways: either by consuming large quantities of glucose, which can lead to more sorbitol production in the intestine, or by consuming large amounts of sorbitol directly. Even individuals with beneficial gut bacteria may eventually exceed their microbes’ ability to process sorbitol. Sorbitol is one of several compounds known as polyols, or sugar alcohols, which are used in food because they offer sweetness with fewer calories than regular sugar. It was commonly believed that these substances are mostly excreted without affecting metabolism. However, the new findings suggest that the story is more complex. The research reinforces a growing understanding that simply replacing sugar with another sweetener may not eliminate metabolic risks. As Patti noted, there is no "free lunch" when seeking sugar alternatives, since multiple pathways can lead to liver-related issues.