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

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.

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.

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.

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.