The Gut-Brain Axis

Written by health writer Gerda Venter

Medically reviewed by Dr. Daniela Steyn

The gut can also be referred to as the body’s “second brain.” The reason for this is that the gut creates so many neuro-transmitting chemicals responsible for the way we feel. Connecting the gut and the brain might sound a little dramatic, but if you consider that we often refer to a feeling as having a “gut feel,” research has shown a definite relationship.

The gut-brain axis describes the two-way connection and communication between the gut and the brain. The study of the gut-brain axis is one of the most cutting-edge areas of research to date. We now better understand how the connection can impact physical and digestive issues and mental health conditions like depression and anxiety.

How does the gut-brain axis work?

In short, the gut and the brain are connected through the largest nerve in the body, called the Vagus nerve. The gut and the brain communicate through this nerve connection that runs from your brainstem to your intestines. All the microbes in the gut have access to that enteric nervous system via the Vagus nerve. This nerve also gives them direct access to the brain and vice versa. All-day long, they talk to each other and relay messages back and forth.

In addition to the Vagus nerve, other pathways involved in the complex functioning of the gut-brain axis exist. These pathways include communication through various chemical messengers, the endocrine system, gut hormones, and neurotransmitters. Many of our hormones and neurotransmitters are made in the gut. Some examples are gamma-aminobutyric acid (GABA), dopamine and serotonin. Therefore, what is happening in the gut can directly influence our brain function and behavior.

Together, the gut-brain axis is a complex interconnected circuit. This means that when an issue arises at any point within these communication loops, it can affect the whole system. Several health conditions, such as IBS, depression, anxiety, obesity, autism, and more, may arise when this happens. Keeping the gut microbiota healthy will lead to a healthy brain and subsequently a healthy mind and body.

The Gut-Brain Axis and Digestive Disorders

Did you know that only 10% of your body is controlled by your cells and DNA? The other 90% of your functioning comes from the trillions of microbes living in and on you. This microbial ecosystem is called the microbiome. The microbiome includes viruses, bacteria, protozoa, and all kinds of living organisms. It encompasses all the microorganisms and their genetic elements in and on their host (us). The gut has the highest concentration of microbes in the entire body. Microbes have genetic factors that regulate all sorts of functions, including hormone production, metabolic activity, appetite, mood, and sleep.

Whenever changes in the communication between the gut, brain and gut microbiota occur, you are at risk of developing digestive disorders like Irritable Bowel Syndrome (IBS). Changes in communication might happen when you go through a period of high stress, too little sleep, or bad eating habits.

When under stress, the body’s in-built fight-or-flight response is activated. The fight-or-flight response is the body’s natural survival reaction that occurs in response to a perceived threat. When activated, digestion slows as the body uses its energy resources on the danger at hand, increasing gut sensitivity. As a result, the gut function is altered, and IBS gut symptoms of bloating, stomach pain, wind and altered bowel habits are worsened. Having a healthy gut is therefore crucial for a healthy life.