The gut-brain axis: indexed research register 2020–2026

Article overview

A provenance-preserving register of the peer-reviewed literature Europe PMC indexes for the gut-brain axis, with publication types, journal spread and anchor records that any reader can resolve by DOI.

What this register counts

This page reports how much peer-reviewed literature is indexed on the gut-brain axis, not what that literature concludes. Every headline number comes from a live query against the whole Europe PMC index for the term “gut-brain axis”, restricted to a first publication date between 2020-01-01 and 2026-07-26, and each query is published as a link you can open and re-run. On 2026-07-26 the term resolved to 25,229 records. These are complete counts over the index, not estimates and not a sample. A catalogue count is still a measurement of a catalogue, and a catalogue is not the state of knowledge.

Publication types and access

Publication type comes from the index metadata rather than from any reading of the articles. Of the 25,229 records, the index types 11,187 as a review or meta-analysis and 412 as a randomised controlled trial. 19,549 records are flagged open access, which means their full text can be read without payment and a reader can check any statement against the source. Records may carry more than one type, and records with no type assigned are counted in the total but in neither category, so the categories do not sum to the total and were never intended to.

How the literature is distributed

Counts by publication year run 2020: 1,533, 2021: 2,368, 2022: 3,139, 2023: 3,411, 2024: 4,153, 2025: 6,561, 2026: 4,012, with 2025 the heaviest year in the window. Within the 251 records Metatron Health holds in its dated local snapshot of 2026-07-26, the literature spans 138 distinct journals, led by: Frontiers in microbiology (9 records), Nutrients (7 records), Frontiers in immunology (7 records), Frontiers in neuroscience (7 records), Scientific reports (6 records). That journal breakdown describes the captured snapshot rather than the full index, and is offered as an orientation to where this field publishes, not as a complete ranking.

What this register does not establish

A record count is not evidence of benefit, and being indexed is not endorsement by anyone, including us. This page carries no effect estimate, no comparison between treatments, no dose and no recommendation. A large literature can be large because a question is hard, commercially interesting, or repeatedly studied at low quality, and a captured subset can over-represent whichever records the index returned first. Anyone using this register to decide what to take or which practitioner to see is using it for something it was not built to do.

Anchor records and how to verify them

Each register names anchor records that a reader can resolve independently: Food & function (2026); Periodontology 2000 (2026); Probiotics and antimicrobial proteins (2026); Translational psychiatry (2026). Anchors are selected deterministically, favouring reviews and trials, then open access, then citation count, with one record per journal. Records carrying a retraction or withdrawal notice in the index are excluded. Every anchor carries a DOI, its indexed grant support and its correction state as observed on 2026-07-26. Before this page was published, an independent review lane resolved every source URL listed below and recorded the hash of what it received.

Machine-readable reviewed statements

Sources and governing contracts

• SRC-EPMC-INDEX-GUT-BRAIN-AXIS — Europe PMC, EMBL-EBI, Europe PMC search index, records of any type: "gut-brain axis" AND FIRST_PDATE:[2020-01-01 TO 2026-07-26]. Role: bibliographic index. Public literature index operated by EMBL-EBI. Metatron Health has no commercial or editorial relationship with the index operator and receives no payment connected to what it indexes. Open source
• SRC-EPMC-REVIEWS-GUT-BRAIN-AXIS — Europe PMC, EMBL-EBI, Europe PMC search index, records typed as a review or meta-analysis: "gut-brain axis" AND FIRST_PDATE:[2020-01-01 TO 2026-07-26] AND PUB_TYPE:"Review". Role: bibliographic index. Public literature index operated by EMBL-EBI. Metatron Health has no commercial or editorial relationship with the index operator and receives no payment connected to what it indexes. Open source
• SRC-EPMC-TRIALS-GUT-BRAIN-AXIS — Europe PMC, EMBL-EBI, Europe PMC search index, records typed as a randomised controlled trial: "gut-brain axis" AND FIRST_PDATE:[2020-01-01 TO 2026-07-26] AND PUB_TYPE:"Randomized Controlled Trial". Role: bibliographic index. Public literature index operated by EMBL-EBI. Metatron Health has no commercial or editorial relationship with the index operator and receives no payment connected to what it indexes. Open source
• SRC-EPMC-OPENACCESS-GUT-BRAIN-AXIS — Europe PMC, EMBL-EBI, Europe PMC search index, records whose full text is free to read: "gut-brain axis" AND FIRST_PDATE:[2020-01-01 TO 2026-07-26] AND OPEN_ACCESS:y. Role: bibliographic index. Public literature index operated by EMBL-EBI. Metatron Health has no commercial or editorial relationship with the index operator and receives no payment connected to what it indexes. Open source
• SRC-EPMC-GUT-BRAIN-AXIS-01 — Food & function, Dietary polyphenols as modulators of the microbiota-gut-brain axis in depression and anxiety: a preclinical perspective. Role: independent research. Independent peer-reviewed article. Metatron Health has no financial or editorial relationship with its authors, journal or funders and earns nothing from citing it. Open source
• SRC-EPMC-GUT-BRAIN-AXIS-02 — Periodontology 2000, Of mice and men-The emerging oral-gut-brain axis of health and disease. Role: independent research. Independent peer-reviewed article. Metatron Health has no financial or editorial relationship with its authors, journal or funders and earns nothing from citing it. Open source
• SRC-EPMC-GUT-BRAIN-AXIS-03 — Probiotics and antimicrobial proteins, Paradigm Shift of Microbiota-gut-brain Axis During Aging: Potential Role of Probiotics to Improve Cognitive Decline. Role: independent research. Independent peer-reviewed article. Metatron Health has no financial or editorial relationship with its authors, journal or funders and earns nothing from citing it. Open source
• SRC-EPMC-GUT-BRAIN-AXIS-04 — Translational psychiatry, Microbiota-gut-brain axis in autism spectrum disorder: integrating brain structure, function, and transcriptomics. Role: independent research. Independent peer-reviewed article. Metatron Health has no financial or editorial relationship with its authors, journal or funders and earns nothing from citing it. Open source