A global consensus establishes a basis for measuring and improving gut health

A new definition of gut health beyond the hype

The large intestine where the majority of our gut microbiome lives, is linked to many aspects of health and disease. While evidence is emerging that it affects everything from how our bodies digest and absorb nutrients to the risk of immune-mediated inflammatory diseases, researchers have not yet proposed a definition of gut health¹.

The new International Scientific Association for Probiotics and Prebiotics (ISAPP)-led scientific consensus establishes a basis for measuring and improving gut health, providing a framework with applications for researchers and clinicians that guide better-informed health decisions for healthy individuals and patients interested in improving gut health².

The consensus defines gut health as “a state of normal gastrointestinal function without active gastrointestinal disease and gut-related symptoms that affect quality of life”. The definition of gut health involves both physiological function and an individual’s experience of their symptoms. In particular, it states that an individual with a diagnosed digestive disorder can experience gut health when symptoms and their impact on physical and mental health are in remission.

The six domains of gut health and how to measure them

Authors from diverse fields, including gastroenterology, nutrition, immunology, and microbiology, suggest that gut physiology comprises 6 domains and propose ways to evaluate them:

• Digestive secretions and motility: measures ready to use in clinical practice include indirect measures of digestive secretions, fecal elastase as a marker of pancreatic exocrine sufficiency, and Bristol stool form for colonic transit.
• Gut microbiome: while there is a lack of consensus on what is a normal or healthy microbiome, the panel acknowledges that fecal short-chain fatty acids are an unreliable marker of gut health because the majority of them are absorbed or metabolized by colonocytes, meaning stool levels do not accurately reflect actual production levels.
• Gut barrier: early and late urinary excretion of mannitol and lactulose is a widely used marker that reflects small and colonic permeability, respectively, whereas fecal zonulin and plasma lipopolysaccharide-binding protein are less reliable markers of gut barrier status.
• Immunity: C-reactive protein is a non-specific marker of inflammation and/or infection and stool calprotectin is commonly used to screen for inflammatory bowel disease.
• Metabolism: the levels of active forms of the hormones GLP1 and PYY may reflect the functional capacity of L cells, while they are not widely available for clinical use.
• Gut-brain axis: multiple host- and gut-microbiota-derived metabolites have potential for diagnosing disorders of gut-brain interaction, while normal ranges are not well established and not validated in clinical populations.

The authors acknowledged that an important limitation identified with many gut physiology-related metrics is their lack of validation against clinically meaningful endpoints. For instance, it is common that symptomatic patients with IBS have no observable changes in objective markers of gut dysfunction. Beyond isolated symptoms and markers of gut dysfunction, the impact of symptoms on daily life remains pivotal, measured by bothersomeness and deterioration in quality of life, and it is also relevant to consider their impact beyond the gut and the context in which they appear (e.g., the menstrual cycle or a trip).

Determinants of gut health: all that glitters is not gold

When it comes to maintaining or restoring gut health, the new consensus recognizes the central role of diet and nutrition on gut health through gut microbiome-dependent and independent mechanisms. While a healthy dietary pattern and lifestyle are undoubtedly essential contributors to overall and gut health, individual foods with simplistic marketing claims that lack strong scientific evidence are less likely to be the holy grail of good gut health, which aligns with previous research^3,4.

It is also common that mainstream dietary interventions for gastrointestinal disorders have a different impact on the different dimensions of gut health. For instance, the low FODMAP diet has benefits for global symptoms of IBS, but leads to reductions in Bifidobacterium, highlighting that dietary recommendations for improving gut health are highly individualized, in particular given the large interindividual variability in the gut microbiome. Beyond diet, other determinants of gut health, less studied, include genetics, early-life exposures, medications, stress, exercise, smoking, and disease.

Overall, the consensus paper provides a framework and roadmap to assist researchers in designing basic, translational, and clinical studies targeting gut health, to assist healthcare providers in the clinical management of gastrointestinal disorders, and to increase awareness among the lay public that the gut microbiome is not the only piece of the puzzle for better gut health.

References:

¹Staudacher HM, Loughman A. Gut health: definitions and determinants. Lancet Gastroenterol Hepatol. 2021; 6(4):269. doi: 10.1016/S2468-1253(21)00071-6.

²Marco ML, Cunningham M, Bischoff SC, et al. The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on the definition and scope of gut health. Nat Rev Gastroenterol Hepatol. 2026. doi: 10.1038/s41575-026-01176-x.

³Bischoff SC. ‘Gut health’: a new objective in medicine? BMC Med. 2011; 9:24. doi: 10.1186/1741-7015-9-24.

⁴Prados-Bo A, Rabassa M, Bosch M, et al. Online information in Spanish on probiotics, yoghurt, kefir, kombucha, fibre and prebiotics: an analysis of the quality of information and the certainty of the evidence supporting health claims. BMJ Open. 2022; 12(8):e063316. doi: 10.1136/bmjopen-2022-063316.