Digestive system is said to be our second brain as it controls all our thoughts and moods.
Secondly digestion is a complex process and our digestive system is bound to do it every single day restlessly cutting,grinding,tearing,absorbing and assimilating the food we eat.
So such a tough task is to be done by our digestive system.
It makes us sense when we are in need of food or when we have eaten stomach full by communicating with our brain.
So for all the above reasons digestive system is termed as second brain.