World Digestive Health Day: Why gut microbiota is called the 'second brain'

The World Gastroenterology Organisation observes World Digestive Health Day on May 29 every year. The day aims to highlight the role of digestive health in overall well-being. The theme for this year is 'Your Digestive Health: Nourish to Flourish'. 

It is known to very few that the gut microbiota is often called the 'second brain'. But why is that? The gut is the second organ in the human body that contains the most neurons after the brain. In fact, it contains about 500 million neurons forming the enteric nervous system.

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The extensive communication between the gut and the brain helps in the digestion process and even alerts the brain when something is amiss. 

Hence, the nerve connections, chemical molecules produced in the gut by human cells or by the microbiota, have an effect on the immune system directly or indirectly. This is constantly communicated between the gut and the brain. 

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This immense crosstalk between the two large nerve centres not just plays a large role, but also impacts our quality of life. 

This can be explained through various situations that we face, for example when someone is anxious or stressed, they might experience abdominal pain or nausea or the feeling of 'butterflies in the tummy'. "Messages travel from gut to brain, too. This helps explain why when we eat something that makes us sick, we instinctively avoid the food and even the place we found it," mentioned a Harvard article titled 'The Gut and the Brain'. 

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