If you have ever had butterflies in your stomach or a gut feeling, then you know something about the gut-brain axis. These sensations coming from your gut suggest that your gut and brain are connected. Studies show that your brain largely affects your gut health and your gut also directly affects your brain’s health. The communication system between your brain and gut is known as the gut-brain axis.

How the brain and the gut are connected

Your gut and brain are connected both biochemically and physically in different ways. Read on to learn more.

The nervous system and the vagus nerve

Neurons are cells in the central nervous system and your brain that tell your body how to react and behave. There are over 100 billion neurons in the brain. Your gut has 500 million neurons. The neurons are connected to your brain through nerves in the nervous system.

The vagus is a large nerve – one of the biggest nerves – that connects your brain and gut. It sends signals in different directions. Studies in humans found that people with IBS had reduced vagal tone and this indicates that they have a reduced function of their vagus nerve.

Another study in mice found that feeding mice with probiotics reduced the amount of stress hormone in their blood.  This shows that the vagus nerve is very important in the connection between the gut and the brain and probiotics for health facilitate this pathway.

Neurotransmitters

Serotonin is an example of a neurotransmitter and it contributes to feelings of happiness and helps control the body clock.

The gut microbes produce a neurotransmitter known as gamma-aminobutyric acid, which controls feelings of anxiety and fear.

Gut microbes also make other chemicals that affect your brain

The microbes that live in your gut make other chemicals that affect the functioning of the brain. The gut microbes produce a lot of short-chain fatty acids such as propionate, butyrate and acetate. They make short-chain fatty acids by digesting fibre. Short-chain fatty acids affect the function of the brain in different ways such as reducing appetite.

The effect of gut microbes on inflammation

If your immune system is on high-alert  for too long, it can cause inflammation which could lead to brain disorders such as Alzheimer’s disease and depression. The gut-brain axis is effective when your immune system is good because the gut and its microbes control inflammation and make different compounds that affect the health of the brain.