Gut Health: Everyone Wants it, but What is It?

“Gut health” easily made any top 5 list of consumer trends in 2025, and it seems to have bumped higher as we close the first quarter of 2026. Interest and investment in gut health through a focus on probiotics, prebioitics, and fiber is expected to increase¹ in 2026. Cousin to “gut health” is the “fibermaxxing” trend, which is ill-defined but basically emphasizes fiber intake, something both scientists and healthcare practitioners would agree is essential to support gut structure and function. Aligned with that, science is clarifying the importance of specific fiber structure, chemistry, and individual microbiome response, pointing to abundant opportunities for continued discovery. New technologies including artificial intelligence² are central to disentangling the complexities that come to light as we learn more.

Despite the common use of the phrase “gut health” there appears to be no consensus definition. But understanding what “gut health” is and how to measure it will support product innovation, dietary guidance, and related research efforts. This goes beyond the reality that a ‘healthy human gut microbiome’ remains elusive and extends to a lack of consensus measures indicative of a “healthy gut”—which could include gut microbiome as well as other aspects.

Gastroenterologists don’t typically use terminology like “gut health” given the focus on identifying and treating disease processes. As one step toward clarity, the International Scientific Association for Probiotics and Prebiotics issued an expert consensus definition³ of ‘gut health’ in 2026 as: “a state of normal gastrointestinal function without active gastrointestinal disease and gut-related symptoms that affect quality of life.”

The field of nutrition works well when outcomes are linked to a validated biomarker—think cholesterol or blood pressure as related to cardiovascular outcomes. But a common challenge in the field is: what is the biomarker for optimized health? How do you know if an intervention is beneficial for the generally healthy population? One approach, which is aligned with regulatory frameworks, is providing evidence that ‘structure and function’ of a specific biological system is maintained.

Foundational to a definition of gut health is a way to measure it. To get a handle on how we can measure this concept of “gut health,” the Nutrition for Gut Health Committee of the Institute for the Advancement of Food and Nutrition Sciences (IAFNS) conducted a systematic review⁴ of measures reflective of “gut health” that are used in the literature as well as those mentioned by professional organizations. This review builds upon a 2011 article⁵ leveraging four domains: measures of function, integrity, immunity, and symptoms.

The IAFNS work focused on systems specific to the gut, recognizing that gut health is intricately linked to other domains of host health (eg the gut-brain axis), and excluded gut microbiome because the translational value of this science is still in development. The work included an assessment of validity and reliability of measures. As part of the process, IAFNS connected with the American Gastroenterological Association for feedback on the approach.

While this work is planned for submission to a peer-reviewed journal, a preview of results illustrates some interesting findings:

• The measures with the most evidence to support validity and reliability are subjective assessments associated with symptoms.
• Reliability and validity data are much weaker for objective measures of integrity, immunity and function.
• The challenge for measures other than symptoms is the heterogeneity of methods, population demographics, presence of a disease or health state, and other variables. As a possibly surprising example, a very commonly used inflammatory marker, calprotectin, is not well validated. However, it is useful in combination with other medical assessments to determine the presence of inflammation and tracking a disease trajectory.
• In terms of what measure or measures are the best candidates to evaluate the presence of “gut health,” or what indices might be the target of nutrition for the generally healthy population, that answer is not immediately evident.

A layer of specificity that IAFNS may take up next is to narrow these markers to those that may be sensitive to nutrition interventions, as the search in this specific project was much broader. As aligned with the ISAPP 2026 expert panel recommendations, it may then be useful to advance validation of commonly used measures, develop normal ranges, and develop an agreed-up set of measures specific to a health outcome and population subgroup. Interest in gut health is likely to expand as we learn more about how the gut-brain axis and gut microbiome influence overall health. However, at present, the path to validate ‘gut health’ benefits through food and nutrition requires additional science.

To support this discovery, IAFNS will continue to work with the food and nutrition community and other scientific organizations. Together, we can advance valid and reliable measures of gut health to ensure that foods, diets, supplements, and related dietary guidance reduce disease risk and support health and well-being.

To learn more about the IAFNS work on gut measures, see the webinar here.

To learn more about the IAFNS Nutrition for Gut Health Committee, visit here.

References

1. 2026 Food & Beverage Trend Predictions. American International Foods Inc. Accessed April 23, 2026. https://www.americaninternationalfoods.com/2026/02/25/2026-food-beverage-trends/
2. Zimmerman S. Ingredion leverages AI to advance ingredient discovery. FoodDive. March 18, 2026. Accessed April 23, 2026. https://www.fooddive.com/news/ingredion-holobiome-shiru-ai-partnership-ingredient-gut-health-fiber/815008/
3. Marco 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:1038/s41575-026-01176-x
4. IAFNS. Documenting the continuum of measures from health to disease. Accessed April 23, 2026. https://iafns.org/documenting-the-continuum-of-measures-from-health-to-disease/
5. Bischoff SC. 'Gut health': a new objective in medicine? BMC Med. 2011;9,24. doi: 10.1186/1741-7015-9-24