The sweet truth may be more bitter than expected. New research from Washington University in St. Louis shows that sorbitol-a common sugar substitute found in "sugar-free" gums, candies, and protein bars-may harm the liver much like fructose, the same sugar long tied to fatty liver disease and metabolic problems.
Artificial sweeteners such as aspartame, sucralose, and sugar alcohols like sorbitol have long been marketed as “healthier” substitutes that help cut calories or manage blood sugar. But scientists are now discovering that some of these sweeteners may disrupt metabolism in surprising ways. Sorbitol, in particular, is so chemically close to fructose that the liver can easily convert it into the same damaging compound.
Led by Professor Gary Patti, a chemist and biologist at WashU, the research team conducted experiments on zebrafish, a model organism often used for studying human metabolism. They found that enzymes in the gut can naturally convert glucose into sorbitol after meals. If the gut bacteria fail to break it down completely, the remaining sorbitol travels to the liver—where it transforms into fructose-like molecules. The effect mirrors the way high-fructose diets trigger liver fat buildup and inflammation, both early signs of steatotic liver disease (fatty liver).
Interestingly, gut microbiota played a pivotal role. Zebrafish with sorbitol-degrading bacteria could process the compound safely, while those lacking these microbes accumulated excess sorbitol, worsening liver stress. This suggests that a person’s unique gut bacterial balance might determine how their body reacts to certain sweeteners. Patti’s team observed that even low doses of sorbitol, similar to what might be consumed in everyday “low-calorie” foods, could end up being converted into harmful metabolic byproducts.
The findings reinforce a growing message among nutrition scientists: there’s no free lunch when it comes to sugar substitutes. While marketed as harmless, sugar alcohols like sorbitol might quietly strain liver health—especially in people with high sugar intake or gut imbalances.
Future research will dig deeper into how diet, microbiota, and metabolism interact to reveal which “sugar-free” choices are truly safe for long-term health.
REFERENCE: Jackstadt, M. M., et al. (2025). Intestine-derived sorbitol drives steatotic liver disease in the absence of gut bacteria. Science Signaling. doi: 10.1126/scisignal.adt3549. https://www.science.org/doi/10.1126/scisignal.adt3549
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