A new study set out to answer a question that has puzzled scientists for years: can the bacteria living in our gut alter the chemistry of the human brain?
In a new study published in the journal Molecular Psychiatry, researchers created one of the most detailed maps to date of the relationship between the gut microbiome and brain neurochemistry, providing new insight into the so-called gut-brain axis
The gut-brain axis refers to the complex communication network linking the digestive system with the central nervous system
Scientists have long suspected that microbes living in the gut may affect mood, memory and mental health, but direct evidence connecting specific bacteria to brain chemicals has remained limited
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Researchers from The University of Surrey compared gut microbial profiles with measures of neurochemistry, looking for links between the bacteria living in the digestive tract and key signaling molecules in the brain
Their analysis identified associations between microbial communities and neurochemical pathways involved in brain function, offering some of the strongest evidence yet that the microbiome may play a role in shaping human neurochemistry
“The differences in associations between the brain regions came as a surprise, because the inferior occipital gyrus was more prominent than expected,” Dr. Nicola Johnstone, lead author of the study, told Newsweek
The inferior occipital gyrus is primarily involved in visual processing and was initially included as what researchers considered a neutral comparison
Instead, it showed the broadest set of microbiome-related associations of any region examined
“It’s made me start thinking about sensory processing as an avenue in gut-brain research,” Johnstone said
The researchers found particularly strong evidence that specific gut microbes were linked to neurochemical processes that help regulate communication between brain cells
Rather than acting through a single pathway, the results suggest gut bacteria may influence multiple neurochemical systems simultaneously, reinforcing the idea that the microbiome is deeply integrated into human biology
The findings add to growing evidence that the trillions of microorganisms residing in the human digestive tract may have effects far beyond digestion
Previous research has linked microbiome changes to conditions including depression, anxiety, autism spectrum disorder and neurodegenerative diseases, although scientists continue to debate whether these microbial shifts are causes, consequences or simply markers of disease
While Johnstone cautioned that the findings are not yet strong enough to support specific mental health recommendations, she said there are already steps people can take to support a healthy microbiome
“Maintaining a broad diet incorporating lots of fiber and nutrients, which feed the same short-chain-fatty-acid-producing bacteria we saw linked to brain chemistry in this study, remains the best route to brain health,” Johnstone said
Johnstone, N., Cohen Kadosh, K. Empirical evidence for gut microbial influence on human brain neurochemistry . https://doi.org/10.1038/s41380-026-03813-y
Contact Newsweek editors on this story: Kara Dolman and Emma Lee-Sang
