How the Gut Peptide PYY May Drive IBS Symptoms — And How Diet Can Fix It

What the researchers found

The review synthesizes several key findings about PYY in IBS:

• PYY concentration and PYY-producing endocrine cell density are decreased in both the colon and rectum of IBS patients

• PYY cell density in the ileum (small intestine) remains unchanged

• The reduced PYY cells may result from decreased stem cell differentiation toward endocrine cell lineages

• PYY regulates intestinal motility, secretion, absorption, and visceral sensitivity by modulating serotonin release

• PYY abnormalities may therefore contribute to the intestinal dysmotility and visceral hypersensitivity characteristic of IBS

• A low-FODMAP diet restores PYY cell density in the large intestine and improves abdominal symptoms in IBS patients

Why it matters

IBS affects an estimated 10-15% of the global population and has no cure. Understanding that a specific peptide abnormality — reduced PYY cells — may underlie key symptoms offers both a mechanistic explanation and a therapeutic target. The finding that a low-FODMAP diet can restore PYY cell density provides a science-backed rationale for dietary management of IBS and could inform future peptide-based therapies.

How the study worked

This is a narrative review synthesizing published research on PYY and its role in IBS pathophysiology. The authors compiled data from studies measuring PYY cell density, PYY concentrations, and the effects of dietary intervention (low-FODMAP diet) on PYY cell populations and IBS symptoms in clinical populations.

What this study cannot tell us

As a narrative review, this synthesizes existing evidence without generating new data. The causal relationship between PYY deficiency and IBS symptoms is proposed but not definitively proven — the reduced PYY cells could be a consequence rather than a cause of IBS. Most referenced studies likely had relatively small sample sizes. The review doesn't address PYY differences across IBS subtypes (IBS-D, IBS-C, IBS-M) in detail.

How to read the evidence

This is a narrative review synthesizing clinical observations and mechanistic data about PYY in IBS. While it draws on human clinical studies, it does not present original data or systematic analysis. The evidence supports a plausible mechanistic hypothesis rather than definitive proof of causation.

When this study was published

Published in 2020, this review is about 6 years old. The low-FODMAP diet continues to be a first-line dietary recommendation for IBS, and PYY research has continued to advance, supporting the relevance of this review's conclusions.

The bigger picture

PYY is part of the gut peptide hormone network that includes GLP-1, CCK, and ghrelin — all of which coordinate digestion, appetite, and gut-brain communication. This review connects PYY deficiency specifically to IBS, a condition that affects hundreds of millions worldwide but remains poorly understood and difficult to treat. The finding that dietary intervention can correct peptide cell populations in the gut represents a paradigm where food serves as medicine at the molecular level.

Questions still open

• Could PYY supplementation or PYY receptor agonists be developed as direct treatments for IBS?
• Do different IBS subtypes (diarrhea-predominant vs. constipation-predominant) show different patterns of PYY cell depletion?
• What specific mechanisms cause PYY cell loss in IBS — is it inflammation, microbiome changes, or altered stem cell signaling?

Common questions

Read the original research

Possible role of peptide YY (PYY) in the pathophysiology of irritable bowel syndrome (IBS).

Neuropeptides, 79, 101973

Citation

El-Salhy, Magdy; Hatlebakk, Jan Gunnar; Hausken, Trygve. (2020). Possible role of peptide YY (PYY) in the pathophysiology of irritable bowel syndrome (IBS).. Neuropeptides, 79, 101973. https://doi.org/10.1016/j.npep.2019.101973