When one hears the term superorganisms”, the first thing that comes to mind is the Marvel Cinematic Universe Superheroes. But, did you know- that you yourself are a superorganism? Turns out, it’s not a necessity to get bitten by a radioactive spider to become a superorganism. Every human being is home to billions of microorganisms including bacteria, fungi, viruses, and many others which either live on or inside the human body. The number of microbiota present in human beings is almost 10 times the total number of human cells!
The most significant population of microorganisms, which make up to 1 kg, inhabit the digestive tract and they are collectively called the “gut microbiota” or the “gut microbiome”. The gut microbiota is actively involved in maintaining human physiology and communicates regularly with other body organs, including our brain.
A two-way communication system exists between the gut and the brain known as the gut-brain axis. There are two main pathways through which this bi-directional communication system operates:
- Neurologic pathway: The enteric nervous system (ENS), present in the intestine (also called the second brain), together with the Vagus nerve make up the neurologic pathway. Various neurotransmitters (GABA, serotonin, melatonin, histamine etc.) responsible for sending direct signals to the brain are produced by the sensory nerves present in the ENS.
- Metabolic pathway: The gut microbiota produce several components known as metabolites which have the ability to cross the blood-brain barrier and can affect the functioning of a special type of brain cells known as microglial cells which are necessary for the proper development of the brain as well as for modulation in the behavior in humans.
We have already touched upon these pathways in our previous article.
However, did you know that the population demographics of the gut microbiota changes rapidly with changes in the external environment? In this case- the gut or the digestive system.
For example, production of biologically active molecules such as peptides, or production of inflammatory molecules such as cytokines in the gut, directly affect the gut microbiota population.
Now that we have had a quick look at how the gut and the brain communicate and what may cause disruptions in this communication (long distance is hard, phew!), we can move on to read about the various ways by which the microbiota residing in us impact our brain activities.
It has been found through various experiments that an imbalance in the gut microbiota (known as dysbiosis), can lead to clinical depression. Long-term swelling (also known as chronic inflammation) that occurs during stress-related disorders leads to changes in gut microbiota reduces serotonin production. The gut is responsible for providing 95% of the total serotonin which is known to play a beneficial role in several functions of the body. Inflammation in the gut can also cause stressful environments for the microbial population and can subsequently lead to symptoms of anxiety and depression.
On the other hand, changes in the gut microbiota can also be caused by on-going stress in an individual. In response to these changes, several metabolites, toxins, and neurohormones are released that can further impact an individual’s mood and eating behavior. The changes in eating behavior can further affect the gut microbiota population, creating a vicious cycle.
Therefore, it is evident that adapting a diet and lifestyle that promotes the growth of beneficial gut microbiota will lead to an optimal utilization of the gut-brain connection and help us maintain good mental health.
Probiotics such as yogurt, cheese, pickles, etc., are found to have species of microorganisms called – Lactobacillus and Bifidobacterium which are key components of a ‘healthy’ gut microbiota. A term called psychobiotic has been recently coined to show their importance in mental disorder therapies as they can act as antidepressants and work against anxiety. Conversely, high-fat diets and highly-refined carbohydrate diets constitute an unhealthy diet that causes an unfavorable changes in the gut microbiota population and thereby can also affect our overall mental health.
Thus, one can safely say that the way to a ‘happy mind and heart’ is through a ‘happy gut’.
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