Despite the established evolutionary importance of stomach acidification in vertebrates, the exact contribution of this process to overall protein digestion, nutrient absorption, growth, energy metabolism and development has not been fully elucidated and is oftentimes subject to extensive scientific debate. This Commentary sets out to frame the current state of our understanding, highlighting unresolved issues and proposing where experimental approaches can be applied to address these questions. Furthermore, we explore in depth the tantalizing evolutionary and physiological puzzle of repeated loss of gastric function in fishes. In this way, we hope to help clarify the role of the gastric proton pump and stomach acidification in digestion, metabolism and growth in vertebrates.

Keywords:
Acidification, Secondary loss, Digestion, Knockout, Gastric proton pump, Microbiome

Funding

This work was supported by Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery grant RGPIN-2019-06838 to J.M.W.

ECR Spotlight

This article has an associated ECR Spotlight interview with Patrícia Ferreira.

Special Issue

This article is part of the special issue ‘The Integrative Biology of the Gut’, guest edited by Carol Bucking, Matt Regan and John Terblanche. See related articles at https://journals.biologists.com/jeb/issue/228/14.

© 2025. Published by The Company of Biologists
2025
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