Walk down the aisles of many grocery stores and you're liable to see claims about products that are "good for gut health," from yogurt and kombucha to supplements and even sodas. But despite its popularity, the phrase can mean different things to different people and lacks a shared scientific definition.
Scientists, clinicians, food companies and consumers widely use the term "gut health," particularly in research and marketing tied to diet, fermented foods, probiotics, prebiotics and the gut microbiome.
"For years, we were all using the term gut health, but we weren't using it in the same way," said Maria Marco, a professor in the Department of Food Science and Technology at the University of California, Davis, and lead author of a new consensus study. "For some, poor gut health meant just having an upset stomach, acid reflux or constipation, symptoms centered in the digestive tract. Others defined it much more broadly, including allergies and depression."
Marco said that lack of agreement made it hard to know how to evaluate or compare research studies.
International panel proposes a clear definition
To address the confusion, an international group of scientists and clinicians has taken a closer look at what gut health means. They proposed a scientific definition along with practical ways to measure it.
In September of 2024, the nonprofit International Scientific Association for Probiotics and Prebiotics, or ISAPP, convened an expert panel jointly led by Marco and Eamonn E. Quigley of Houston Methodist Hospital. The panel defined gut health as "a state of normal gastrointestinal function without active gastrointestinal disease or gut-related symptoms that affect quality of life." Their consensus statement was published in Nature Reviews Gastroenterology & Hepatology.
The definition matters because "gut health" now influences what people buy, even though people use the term vaguely and inconsistently. Also, symptoms and disease do not always align.
"People may feel fine, but have active disease and vice versa," Marco said.
While doctors may diagnose someone with celiac disease or inflammatory bowel disease, the patient may still experience gut health during periods of complete remission. Measurements of gut health should go beyond lab tests or the gut microbiome to include both how well the digestive system functions and how people feel day to day.
Implications for medicine, research and consumer claims
In the consensus statement, the panel outlines clinically relevant ways to assess gut health and proposes a framework that physicians can use in medical practice and researchers can use in studies on food, probiotics and other dietary interventions.
The authors also note that reliable tests to measure gut health, particularly the gut microbiome, remain limited and there is still a need for better tools and more consistent study designs.
Researchers described the new definition as a starting point for a more comprehensive analysis for understanding what contributes to a healthy gut and how it influences overall health.
Other authors include Marla Cunningham, Stephan C. Bischoff, Gerard Clarke, Nathalie Delzenne, James D. Lewis, Marlies Meisel, Daniel Merenstein, Paul W. O'Toole, Heidi M. Staudacher, Hania Szajewska, Jerry M. Wells and Eamonn M. M. Quigley.
Marco is president of ISAPP's board, a voluntary unpaid position. The authors received travel support from ISAPP to attend the initial panel meeting and discussion.
