Defining Gut Health: ISAPP Consensus Statement Gives Clinicians a Practical Framework

For years, the term “gut health” has been everywhere — in journals, clinic conversations and, perhaps most prominently, on product labels. Despite its popularity, what it lacks is precision. A new consensus statement from the International Scientific Association for Probiotics and Prebiotics (ISAPP) aims to change that — giving gastroenterologists a clinically actionable definition and a framework for evaluating gut function in practice.

Co-chaired by Houston Methodist Chief of Gastroenterology Dr. Eamonn Quigley, the effort brings together international panel of experts across microbiology, physiology, nutrition and clinical medicine to answer a deceptively simple question: What do we actually mean by gut health?

The consensus statement, published in Nature Reviews, comes at a time when research into the microbiome, diet and gut-brain interactions is accelerating, often outpacing the field’s ability to define what constitutes normal.

From catchphrase to clinical concept

“A lot of people use the term 'gut health' very loosely — particularly in the media and in marketing — but nobody really knows what it mean. With this paper, we tried to put some real evidence around this concept.”

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Eamonn Quigley, MD

The group’s proposed definition centers on a “state of normal gastrointestinal function,” grounded in the absence of active disease and the presence of coordinated processes supporting digestion, absorption and host-microbe interactions.

Importantly, the definition acknowledges nuance: patients with conditions such as celiac disease or inflammatory bowel disease may still achieve gut health if their disease is in remission and symptoms no longer affect quality of life.

“That was a key point for us,” says Dr. Quigley. “If someone’s disease is fully controlled and their gut is functioning normally, we would consider that gut health."

A framework grounded in biology

Beyond definition, the paper’s most practical contribution may be its structured framework. The authors outline multiple biological domains — including microbiome composition, gut barrier integrity, immune activity, motility and gut-brain interactions — and attempt to map how each contributes to gut health and how it might be measured.

Central to that effort is a comprehensive table summarizing available metrics of gastrointestinal function across these domains, along with their clinical utility.

“That’s really the heart of the paper,” Dr. Quigley explains. “It’s our best attempt to compile what can be measured, how it can be measured and how useful those measures are in clinical practice."

For practicing clinicians, the implications are immediate. The consensus clarifies which tools are ready for clinical use — such as symptom-based assessments and established physiological tests — and which remain investigational. Microbiome testing, for example, remains an area of intense research but limited clinical applicability due to a lack of consensus on what constitutes “normal.”

“We can analyze the microbiome in great detail,” says Dr. Quigley. “But at this moment, it’s not particularly helpful for diagnosis in routine practice.”

Looking at symptoms through a clinical lens

In doing so, the framework offers a more consistent way to distinguish benign, intermittent symptoms from those that warrant further evaluation — a distinction that aligns closely with how clinicians already approach disorders of gut-brain interaction.

“If we said any GI symptom meant you didn’t have gut health, then nobody would be healthy,” notes Dr. Quigley. “We all get some of these issues sometimes. What matters is when symptoms become bothersome and impact daily life.”

For researchers, the consensus provides a common language that could standardize study design and interpretation across the field. And for industry, it raises the bar for how “gut health” claims are used and understood.

“This doesn’t carry regulatory authority,” Dr. Quigley notes. “But it does put the onus on anyone using the term to think more carefully about what they mean.”

The work underscores Houston Methodist’s role in shaping how emerging areas of gastroenterology are defined and translated into clinical practice. From his longstanding contributions to Rome criteria to his leadership in microbiome research, Dr. Quigley’s involvement in this effort reflects a career spent bringing clarity to complex, evolving areas of GI medicine.

“It’s a starting point,” Dr. Quigley says, “and one we expect will evolve as the science advances.”