Your second brain - the gut brain

Your second brain – the gut brain

We’re all familiar with our brain, and the idea of it being the control centre for our body. However, we’ve all got a second brain too – our gut brain.

What is the gut brain?

It is our Enteric Nervous System, or ENS. It’s a network of around 500,000 nerve cells in our gut wall, and is as large and as complex as your spinal cord. It doesn’t just control our entire gastrointestinal system, it can function independently of our ‘head brain’.

How does the gut brain connect to the head brain?

The two brains communicate via the vagus nerve. Messages are sent in both directions, and the messages from the gut brain are sophisticated too.

Take the example of feeling full after a meal, when your stomach can have stretched from the equivalent of 8 teaspoons up to the equivalent of a 2 litre soft drink bottle. The assumption used to be that it was feedback on the amount of stretch that told us when we were full.

It is though much more sophisticated than that. Part of the gut brain’s job is to regulate the production of PYY, a hormone that tells you when you’re full. It also controls the section of the gut that produces ghrelin, the ‘hunger hormone’ that also plays a role in body weight.

Injury to the gut, or problems from an unhealthy gut, can suppress PYY or overproduce ghrelin, leading to increased appetite and weight gain. It’s now understood that gastric surgery works because of it’s effects on the gut brain and hormone production, and not merely because the gut is made smaller.

Does gut feeling come from our gut brain?

If your stomach has ever ‘dropped’ at bad news, or you’ve had that sinking feeling, that is your gut brain in action. You’re stressed, and as your gut brain reacts to that, it send a signal to the head brain. In fact the gut drives our emotional state much more than was previously recognized.

That’s why maintaining a healthy gut is so important for mental as well as physical health.

If you found this blog about your second brain interesting then why not sign up for my monthly newsletter here with three stories every month on the quirky side of psychology and relationships