Diets rich in fiber, fruits, vegetables and fermented foods favor bacterial diversity, while frequent consumption of ultra-processed foods, alcohol or antibiotics can alter it, Credit: mineducacion.gov.co
At first glance, the intestine and the brain appear to be at a considerable distance from each other in the human body, with no connections other than nerve signals with their respective impulses and ‘orders’. But there are also microorganisms in the intestine that could influence the functioning of the brain and mental health, making the distance between these two organs much shorter than one might imagine.
This communication takes place through the so-called gut-brain axis, a connection mediated mainly by the vagus nerve, which extends from the brain to organs in the chest and abdomen such as the stomach and the intestine, and allows interaction between the nervous system and the intestinal microbiota, made up of bacteria, fungi and viruses, among other microorganisms, explains a bulletin from the News Agency of the National University (UNAL).
What is surprising is that this system participates in processes such as memory, emotions, mood, stress response, inflammation and the production of neurotransmitters, which explains why intestinal health can influence the functioning of the brain.
Parkinson’s disease and intestinal bacteria
“In Colombian patients with neurodegenerative diseases (in which the brain gradually loses its functions), particular compositions of intestinal microbiota have been identified that differ from those of healthy individuals, not so much due to the presence of different bacteria, but because of the abundance of certain microorganisms and the compounds they produce,” explains Professor Andres Mauricio Pinzon Velasco, from the Laboratory of Bioinformatics and Systems Biology of the Institute of Genetics (IGUN) of UNAL, as cited by the agency.
For example, in studies on Parkinson’s, researchers have found that some patients have a greater amount of bacteria associated with the production of certain substances generated during digestion and food processing, in addition to a lower presence of microorganisms that produce the amino acids necessary for the body to manufacture neurotransmitters. “These differences would influence processes in the nervous system, although they are still hypotheses that need further research,” adds Pinzon Velasco.
To understand these relationships, in the laboratory the intestinal microbiota of patients and healthy individuals is compared with computational models developed by the research group itself to simulate how hundreds or thousands of bacteria interact within the intestine. These simulations make it possible to identify which microorganisms compete for nutrients, which complement each other and how these interactions change in the presence of disease, the agency continues.
These analyses would open the door to personalized strategies both to improve intestinal health and to eventually support the management of some diseases. Such strategies include changes in diet, the use of specific probiotics or prebiotics, and other interventions aimed at promoting beneficial bacteria.
An ecosystem that changes with life
“The intestinal microbiota is a dynamic system that can be modified throughout life,” explains Professor Pinzon Velasco. “Its composition is influenced by factors such as the type of birth, diet, use of antibiotics, exercise and lifestyle. Human beings coexist with millions of bacteria in different parts of the body, and many of them are essential for health.”
To illustrate the concept, Pinzon Velasco presents the case of people born by vaginal delivery, who tend to have greater bacterial diversity than those born by cesarean section, due to the initial contact of the fetus with the maternal microbiota during birth. Although this is one of the first sources of bacterial diversity, the microbiota can change over time.
Diet also plays a central role. Diets rich in fiber, fruits, vegetables and fermented foods favor bacterial diversity, while frequent consumption of ultra-processed foods, alcohol or antibiotics can alter it. In addition, some intestinal bacteria produce substances that can affect intestinal permeability and allow compounds to pass into the bloodstream, which would influence different health processes.
Regarding fermented foods—both traditional (chicha, guarapo or masato) and processed (yogurt or kefir)—the professor notes that they can help strengthen the intestinal microbiota, especially when consumed without excess sugar. Other commonly consumed foods, such as cassava, can also promote the growth of beneficial bacteria.
Understanding the relationship between intestinal bacteria and the brain would help better explain how biological, environmental and lifestyle factors influence mental and neurological health, and open new possibilities for research in medicine and neuroscience.