Have you ever had a premonition that you experience intensely in your gut or even butterflies in your stomach? All this is not accidental and indicates that our brain and gastrointestinal system are very closely connected. This communication system between the gut and the brain is called the Gut-Brain Axis (GBA).
More and more researchers show that the brain affects the health of the intestine, and vice versa, our gastrointestinal system seems to affect the health of our brain. The way these two very basic organs communicate is both physiological and biochemical.
Physiological Connection
Normal connection is achieved through our vast and complex nervous system. Neurons are cells of the brain and form the central nervous system (CNS). They are estimated to number 100 billion in the brain. Equally interesting, however, is that there are 500 million neurons in the gut, connected to the brain (3). In particular, the pneumogastric nerve has been found to play an important role in communication between the brain and the intestine, as it is one of the largest nerves connecting these two organs and can send "signals" in both directions (4).
Biochemical Binding
These "signals" are called neurotransmitters and are the biochemical way of communication between the brain and the gut. Neurotransmitters are produced in the brain and give the "commands" for our behavior and emotions. A well-known example is the neurotransmitter Serotonin, which is responsible for the feeling of joy and helps in the smooth functioning of the circadian rhythm (5). The interesting thing is that many of these neurotransmitters are also produced in the gut by intestinal cells and by the thousands of bacteria that normally live there. A large amount of serotonin is also produced in the intestine thanks to the abovementioned bacteria (6).
The gut microbiome
Bacteria that normally live and colonize the gut form the gut microbiome and are also responsible for producing another neurotransmitter, γ-aminobutyric acid (GABA), which helps to calm the feelings of anxiety and fear (7).
The gut microbiome is also responsible for the production of other substances that affect the way our brain works. Some of these are Short Chain Fatty Acids (SCFAs), such as propionic, butyric, and acetic acid. These arise from the digestion of fiber and have multiple effects on the brain, eg the reduction of appetite (8).
The question that arises, then, is whether we can, in a safe and effective way, help this connection between brain and gut, so that we can enjoy its benefits.
Consumption of probiotics, ie living microorganisms, which are normally found in our body, can benefit the health of the brain. GBA-targeted probiotics are called "psychobiotics" and appear to help treat anxiety, stress and depression (9). Prebiotics, which are the food of probiotics, also help in the activity of probiotics. Consequently, our diet also plays a very important role in the proper functioning of the GBA.
Take home message: GBA refers to the connection between the brain and the gut, through a network of millions of neurons. The neurotransmitters carried through this network form the communication between the gut and the brain. By changing the type or amount of intestinal microbiome it is possible to affect the health of our brain.
Bibliography
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4367209/
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2776484/
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3845678/
- https://pubmed.ncbi.nlm.nih.gov/29593576/
- https://pubmed.ncbi.nlm.nih.gov/12851635/
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4393509/
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5127831/
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4756104/
- https://pubmed.ncbi.nlm.nih.gov/23759244/