We hear a lot these days about the gut-brain axis, but what is it, how does it work and what does it mean? And what has the gut microbiome got to do with it all? The concept of the gut microbiome started to gain traction in scientific circles as far back as the late 1980s, says Dr Paul Clayton, a leader in the field of nutrition who has written several books, including . Gershon’s work has encouraged generations of doctors and researchers to explore the link between the two. In a study, they added probiotics and prebiotics to the diets of participants for seven weeks to boost the good bacteria in their gut microbiomes, and had them play a game.

One player was given a sum of money to split however they liked with a second player, who was free to decline the offer if they deemed it unfair – in which case neither player received any money. The good-bacteria boost was found to increase participants’ willingness to decline cash when they felt unfairly treated. The participants in the study who were able to apply emotional and cognitive “brakes” and keep a level head in stressful situations were found to have healthier guts.

Some doctors hypothesise leaky gut syndrome may contribute to depression and other mental health disorders. This in turn triggers inflammation of the nervous tissue, which has multiple negative effects, Clayton says. In the short term it can lead to anxiety, depression, reduced impulse control and social withdrawal.

In the longer term it can even lead.