How does gut bacteria affect mood?

Apr 27, 2018

This article was originally published by the BBC on 24 April 2018 and can be accessed here.

The emerging concept that gut bacteria can alter our brains has caused some controversy. Science is telling the story of how the trillions of microbes that live on and in us affect our physical health.

Groups of researchers believe themselves to be on the cusp of a revolutionary discovery that uses “mood microbes” to treat mental health conditions. The concept is based on a study that took place at Kyushu University in Japan:

“The researchers showed that “germ-free” mice – those that never came into contact with microbes – pumped out twice the amount of stress hormone when distressed than normal mice.

The animals were identical except for their microbes. It was a strong hint that the difference was a result of their micro-organisms.”

How could bacteria be altering our brain?

The brain is the most complex object in the known universe so how could it be reacting to bacteria in the gut?

  • One route is the vagus nerve, it’s an information superhighway connecting the brain and the gut.
  • Bacteria break down fibre in the diet into chemicals called short-chain fatty acids, which can have effects throughout the body.
  • The microbiome influences the immune system, which has also been implicated in brain disorders.
  • There is even emerging evidence that gut bugs could be using tiny strips of genetic code called microRNAs to alter how DNA works in nerve cells.

Early evidence links

The evidence linking the microbiome and the brain is as fascinating as it is early. But the pioneers of this field see an exciting prospect on the horizon – a whole new way of influencing our health and wellbeing.

If microbes do influence our brains then maybe we can change our microbes for the better. For example, changing the course of depression; there is already talk of psychiatrists prescribing mood microbes to boost our mental health.

The microbiome – our second genome – is opening up an entirely new way of doing medicine and its role is being investigated in nearly every disease you can imagine including allergies, cancer and obesity.