If one day you were feeling rather down, and you started to Google things that may help you, would you laugh if transplanting someone else’s faeces into you was suggested? In this blog I will explain why this might not be such a bad idea after all, as terrible as it sounds.
How did a change in gut microbiota change a mice’s personality? In a lab in Ontario, a gastroenterology researcher called Premysl Bercik conducted a rather interesting experiment on mice. He had two mice as his subjects, one that appeared to be anxious and shy, hiding in its cage and the second mouse was completely opposite in behaviour, acting confidently. He took stools from the two mice and put them inside each other’s stomachs. This is known as a faceal transplant. After 3 weeks, he made an observation of the behaviour of the two mice and noticed that the two mice had essentially swapped personalities (1). After hearing about this experiment, I was intrigued to find out how on earth anything in faeces could possibly alter an individual so drastically.
The gut brain axis was responsible for this happening. The gut brain axis involves biochemical signalling that takes place between the gastrointestinal tract and the central nervous system. The gut contains 500 million neurons which are connected to the brain by nerves, including the Vagus nerve. This nerve is bidirectional which means it sends signals in both ways. In animal studies, it was discovered that stress inhibits signals sent through the Vagus nerve, causing gastrointestinal problems(2).
How may gastrointestinal problems affect your mental health? Many neurotransmitters, such as serotonin, are produced in the gut. Many medications used to treat depression and mental health disorders eg Prozac are serotonin reuptake inhibitors. Serotonin is sometimes known as the happy chemical as it regulates mood and low serotonin levels are often associated with depression. 95% of your body’s serotonin is produced in the gut and is contained in cells in the gut. The fitness of these cells is influenced by what we eat, by chemicals released from certain gut microbes and by signals from the brain. This means that having an unhealthy gut could negatively affect serotonin levels in an individual.
All of these neurons, nerves and neurotransmitters are part of the enteric nervous system (ENS). Almost 90% of the cells in the ENS carry information to the brain rather than receiving messages from it, making your gut as influential to your mood as your head is. (3)