A new study from the University of Surrey and the University of Roehampton has found that the neuroactive potential of bacteria living in the human gut is associated with levels of key brain chemicals, offering fresh human evidence for a biological link between the microbiome and brain function.
Human data adds to the gut-brain evidence base
Published in Molecular Psychiatry, the research examined 61 healthy young women aged 17-25 and combined proton magnetic resonance spectroscopy with shotgun metagenomic sequencing of stool samples. The team reported that microbial pathways involved in producing and breaking down neuroactive compounds were associated with levels of GABA and glutamate in specific regions of the brain.
The findings matter because GABA and glutamate are central chemical messengers in the nervous system, and their balance is closely tied to cognition, neuroplasticity and mental health. Until now, much of the evidence connecting the gut microbiome to these brain systems has come from animal and preclinical research.
Different brain regions showed different microbial links
The researchers said the relationship was not uniform across the brain. Instead, different microbial pathways were linked to GABA, glutamate and excitatory/inhibitory balance in different regions, suggesting a more regionally specific gut-brain axis than previously assumed. The inferior occipital gyrus showed the broadest range of associations, while the anterior cingulate cortex and dorsolateral prefrontal cortex showed more selective patterns.
The study also reported associations between specific gut microbial pathways and self-reported anxiety, depressive symptoms and sleep quality. A GABA-related microbial pathway was linked to trait and social anxiety, while pathways involved in tryptophan metabolism were associated with depressive symptoms and social anxiety.
Why the findings matter for future research
Researchers involved in the work said the study connects microbial genes in the gut, neurochemistry in the brain and psychological measures in the same participants, which could help guide future investigations into the mechanisms behind mental health and brain function. The authors described the results as an early step toward understanding how the microbiome may influence the brain in living people.
The study is titled Empirical evidence for gut microbial influence on human brain neurochemistry via the gut–brain axis.
Medical research groups in the UK continue to focus on mechanisms that could eventually inform better prevention, diagnosis and treatment strategies, from microbiome science to disease-specific clinical studies. Recent MRC and Nature coverage shows that work in this field remains highly active across the UK research ecosystem.
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