Global mental health benefits from expanding microbiome–gut–brain axis research to the global south

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.