Abstract
The microbiome–gut–brain axis is shaped by environmental factors, and increasing evidence suggests that the axis sustains brain health. However, most research is conducted in high-income countries (HICs). Although calls to expand this research into low- and middle-income countries (LMICs) are often grounded in solidarity constructs, they overlook an equally crucial aspect: studying the axis in LMICs offers an innovative route to derive concrete mental health benefits globally. Here we provide three arguments to justify why expanding the geographic boundaries of microbiome–gut–brain axis research supports global relevance and warn about the consequences of failing to do so. The overrepresentation of HICs may (1) lead to distortion of our understanding of the role of the microbiome–gut–brain axis in mental health; (2) lead us to miss a unique opportunity to disentangle complex environmental forces through studying ‘natural experiments’ occurring in LMICs, and (3) limit the development of global mental health interventions derived from lifestyles in LMICs. We thus argue that expanding microbiome–gut–brain axis research in LMICs is not just ethically desirable; it is a duty of scientific rigor with potential to yield global mental health benefits.
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Acknowledgements
We thank E. Schneider, S. Silva-Solar and R. Balasubramanian for their help discussing the content of this manuscript
Funding
APC Microbiome Ireland is funded by Research Ireland (previously Science Foundation Ireland, SFI grant code 12/RC/2273_P2). L.H.M. is supported by the National Council for Scientific and Technological Development (CNPq, Brazil) through the ‘Conhecimento Brasil’ Fellowship Program (grant no. 446495/2024-7). L.J.H. is supported by a Wellcome Investigator Award (220540/Z/20/A) and the Biotechnology and Biological Sciences Research Council (BBSRC) through BBSRC Institute Strategic Programme Food Microbiome and Health (BB/X011054/1) and its constituent project BBS/E/QU/230001B.
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APC Microbiome Ireland, University College Cork, Cork, Ireland
Benjamin Valderrama, Aonghus Lavelle, Gerard Clarke & John F. Cryan
Department of Anatomy and Neuroscience, University College Cork, Cork, Ireland
Benjamin Valderrama, Aonghus Lavelle & John F. Cryan
Department of Microbiology, Immunology and Parasitology, Federal University of Santa Catarina, Florianópolis, Brazil
Livia H. Morais
Department of Psychiatry, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town, South Africa
Sian M. J. Hemmings
South African Medical Research Council/Stellenbosch University Genomics of Brain Disorders Unit, Department of Psychiatry, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town, South Africa
Sian M. J. Hemmings
Department of Microbes, Infection, and Microbiomes, School of Infection, Inflammation and Immunology, College of Medicine and Health, University of Birmingham, Birmingham, UK
Lindsay J. Hall
Food, Microbiome and Health, Quadram Institute, Norwich, UK
Lindsay J. Hall
Brain and Mind Institute, Aga Khan University, Nairobi, Kenya
Zul Merali
Department of Psychiatry and Neurobehavioural Science, University College Cork, Cork, Ireland
Gerard Clarke
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B.V. prepared the first draft and figures. L.H.M., A.L., S.M.J.H., L.J.H., Z.M., G.C. and J.F.C. appraised, edited and revised the text. All authors agree with the content of the article
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J.F.C. has been an invited speaker at conferences organized by Bromotech, Yakult and Nestle and has received research funding from Nutricia, Dupont/IFF and Nestle. G.C. has received honoraria from Janssen, Probi, Apsen, Heel Pharmaceuticals and Ingelhem Boehringer as an invited speaker; is in receipt of research funding from Pharmavite, Fonterra, Reckitt, Nestle and Tate and Lyle; and has been paid for consultancy work by Yakult, Zentiva, Bayer Healthcare and Heel Pharmaceuticals. This support neither influenced nor constrained the content of this manuscript. The remaining authors declare no competing interests.
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Valderrama, B., Morais, L.H., Lavelle, A. et al. Global mental health benefits from expanding microbiome–gut–brain axis research to the global south.
Nat. Mental Health (2026). https://doi.org/10.1038/s44220-026-00690-w
Received:20 November 2025
Accepted:25 June 2026
Published:20 July 2026
Version of record:20 July 2026
DOI
:https://doi.org/10.1038/s44220-026-00690-w
