What is the relationship between exercise, gut microbes, and brain health? Science surprises us.

A new study from the Cajal Neuroscience Center (CNC) of the Spanish National Research Council (CSIC) has identified the gut microbiota as a key factor in the relationship between physical exercise and brain health.

The research, published in the journal eBioMedicine, shows that moderate exercise not only benefits the brain, but also alters the composition of gut bacteria , which could explain some of these positive effects.

The results, obtained in animal models, suggest that the microbiota-gut-brain axis—the two-way communication between the digestive system and the brain —plays a more important role than previously thought in improving cognitive functions such as memory and learning.

The team led by José Luis Trejo, a researcher at the CNC-CSIC, observed that mice that performed moderate physical exercise, for about 40 minutes daily and at an average speed, had greater bacterial diversity in their intestines.

Specifically, an increase in bacterial genera such as Acetatifactor and certain species of the Lachnospiraceae family was recorded, associated with improved cognitive performance in the animals studied.

The research compared different protocols: moderate exercise, prolonged exercise, and high intensity. Scientists found that moderate exercise produced the greatest benefits for memory and neurogenesis (the creation of new neurons), while very high or prolonged intensities did not offer the same improvement.

To confirm whether the changes in the microbiota were just a correlation or had a real effect on the brain , the researchers performed fecal transplants:

Sedentary mice received microbiota from animals that had performed moderate exercise.

Another group received microbiota from mice with long-term exercise.

As for the results, sedentary mice that received the microbiota from moderate runners improved their memory and increased neuron formation in the hippocampus, a brain region linked to learning. In contrast, those that received microbiota from prolonged exercise did not show this effect.

"This causally demonstrates that the cognitive effects of exercise can be mediated, in large part, by the gut microbiota," explained Elisa Cintado, a researcher at the CNC-CSIC and first author of the study.

Several previous studies have already shown that physical exercise can promote the formation of new neuronal connections (synaptogenesis) and increase the size of the hippocampus, the brain region key to memory.

Even research using MRI scans on more than 10,000 people had revealed that those who frequently exercised had larger brain volumes, both in gray matter (information processing) and white matter (connections between brain regions).

The new CSIC study adds a link to this chain: the gut microbiota could be the mediator that connects physical activity with these brain benefits.

Although the study was conducted in animals, the findings suggest that gut microbiota could become a therapeutic target to prevent or delay neurodegenerative diseases, such as Alzheimer's, or to improve cognitive performance in the general population.

The CSIC team emphasizes that human research is still needed to confirm the magnitude of these effects and determine whether they could be translated into clinical treatments.

DANNA VALERIA FIGUEROA RUEDA

DIGITAL REACH EDITORIAL