Didn’t we all have “GUT-WRENCHING” experiences at some point of our lives? Exams and interviews give rise to butterflies in our stomachs, while the thought of public speaking might make some feel nauseous. These phenomena clearly establish that the gut or gastrointestinal tract is sensitive to feelings and can be affected by emotions such as anxiety and sadness, i.e., the brain can affect the gut. But can the Gut affect the brain? Research suggests it does and a Healthline article by Ruairi Robertson brilliantly explains the gut-brain connection.

The biochemical signaling responsible for establishing communication between the gastrointestinal tract and the brain is known as the GUT-BRAIN AXIS. The gut flora, which is the complex community of microorganisms that live in the digestive tracts of humans and other animals, plays a significant role in this communication. The composition of human gut flora changes over time with changing diet and changing health conditions. The gut cells and the microbes of the Gut flora produce many neurotransmitters which control one’s feelings and emotions. Some of the most prominent neurotransmitters produced by the gut are serotonin (which affects feelings of happiness and controls the body clock) and gamma-aminobutyric acid (GABA- which helps control feelings of fear and anxiety). A 2004 study (Nobuyuki Sudo and Yoichi Chida) on laboratory mice revealed that probiotics (live microorganisms promoted with claims that they provide health benefits when consumed, generally by improving or restoring the gut flora) can increase GABA production and reduce anxiety and depression-like behavior in mice. So all the claims of a healthy body leading to a healthy mind weren’t wrong after all!

Neurotransmitters are just one of the many ways through which the gut affects the brain. The gut microbes can produce short chain fatty acids by digesting fiber such as propionate which can reduce appetite along with butyrate which helps in forming the blood-brain barrier (a highly selective semipermeable border that separates the circulating blood from the brain and protects the brain from pathogens). The gut can also affect the brain antagonistically by producing inflammatory toxins such as lipopolysaccharide which is related to brain disorders like dementia and schizophrenia. Thus mental health is completely related to physical health and unhealthy lifestyles are one of the major reasons for widespread cases of depression and suicides in today’s era.

If asked about the number of brains in a human body, many people would consider the answer to be one. Surprisingly research says that there’s evidence of a second brain - the enteric nervous system which is a complex network of more than a hundred million neurons that governs the functions of the gastrointestinal tract. Dr. Michael D. Gershon’s work on this topic is very famous. The enteric nervous system is highly specialized and can work independently of the central nervous system. It can detect if there is any harmful bacteria in the food we are eating and can induce processes such as vomiting and diarrhea thereafter. It also regulates acidity, bowel movement and defense levels of an organism and decides upon the best kind of digestive enzymes required to break down a particular type of food. Thus Gut is the only organ in the body that can function autonomously. Fascinating right? Wait till you read that the gut produces more than 90% of the body’s serotonin as well as about 50% of the body’s dopamine!

However, the enteric nervous system needs to communicate with the central nervous system in cases such as when it needs to signal hunger and fulfillment. It also sends sensations of delight or pleasure to the brain on eating delicious food. ( I always knew that food is an emotion..!) Obviously, as discussed before, it is affected by the emotions the brain is going through, such as stress. Likewise, it can also affect our mood based on the activities and secretions of the intestinal microbes. It communicates with the brain through the Vagus nerve. The connection between diseases such as autism and Parkinson’s disease and the gut flora is also being explored and active research is going on in the same.

All these findings illustrate the importance of nutritious food and healthy lifestyles in maintaining not just good physical health but mental health as well. The gut-feeling is always right for a reason, while what we eat affects how we feel. Essentially, food is not just a way to one’s heart but one’s brain as well!

- Nayanika