Recent studies not only show the importance of the microbiome but also give clear indicators as to how changes in gut bacteria can signal or influence specific health outcomes.
Often referred to as the body’s “second brain,” the gut is increasingly recognised for its role in overall health. New research suggests it may play a direct role in brain aging, while other studies are beginning to identify what a “healthy” gut actually looks like.
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At the heart of this is the microbiome, the collective term for the trillions of microorganisms that inhabit a particular environment, such as the human gut.
Researchers at Stanford Medicine and the Palo Alto–based Arc Institute set out to understand why some people experience cognitive decline earlier than others. “What we learned is that the timeline of memory decline is not hardwired; it’s actively modulated in the body, and the gastrointestinal tract is a critical regulator of this process,” said Christoph Thaiss, PhD, assistant professor of pathology.
The microbiome changes with age
They examined the gut microbiome - the naturally occurring bacterial population in the gut - and found that it changes with age. In older mice, certain groups of bacteria become more common.
These changes are detected by immune cells in the gut, which trigger inflammation. This disrupts communication between the gut and the brain, making it harder for the vagus nerve to send signals to the hippocampus, the region responsible for memory.
When researchers stimulated this nerve in older mice, memory improved significantly: the animals were able to recognise new objects and navigate mazes just as well as younger mice.
“We tend to think of memory decline as a brain-intrinsic process,” Thaiss said. “But this study indicates that we can enhance memory formation and brain activity by changing the composition of the gastrointestinal tract — a kind of remote control for the brain.”
Rather than locating the reason for brain aging solely in the brain, these findings suggest that factors elsewhere in the body, like the gut, play a major role in keeping our minds sharp.
This opens the door to new approaches for protecting memory — from tailored diets and probiotics to therapies that stimulate the vagus nerve.
One step closer to identifying a "healthy" gut
Adding to this picture of gut-brain health, a 2026 study led by the University of Cambridge identified a previously hidden group of gut bacteria called CAG-170. Researchers found that these microbes appear far more often in healthy individuals and are less common in people with chronic diseases.
The team analysed more than 11,000 human gut samples from 39 countries and found that many gut bacteria remain uncultured and underexplored.
These CAG-170 bacteria are stable over time and appear to support other gut microbes while producing vitamin B12, suggesting they play a key role in maintaining a balanced gut ecosystem.
And while some gut bacteria are linked to a healthy microbiome, other bacteria and compounds, known as metabolites, could help detect specific diseases.
Using AI and machine learning, a recent study from the University of Birmingham and University Hospitals Birmingham NHS Foundation Trust identified parts of the microbiome that could aid in detecting and treating gastrointestinal diseases such as colorectal cancer, gastric cancer, and inflammatory bowel disease.
Taken together, the above studies highlight the microbiome as a key regulator of health, influencing important body functions from digestion and disease risk to the aging and function of our brains.
