The ecosystem of bugs in your gut is called the gut microbiota (or gut microbiome) and its relationship with our brain is known as the ‘gut-brain axis’.
We are born with our own unique ecosystem of microbes that exist symbiotically with our bodies (this means we both benefit). How this ecosystem is made up is initially influenced by our mother’s microbiota. There is also some evidence to suggest that the way we are born (caesarean vs vaginal birth) can affect our microbiome.
As we age, we develop individual microbiome ecosystems. These can be influenced by a range of genetic and lifestyle factors. For example, eating lots of processed or junk food which are high in fat and sugar, lack of physical activity, smoking or antibiotics do not help the gut microbiota.
Our gut’s ecosystem has been shown to impact the levels of chemicals influencing the brain. This influences our mood. At the same time mental stress and low mood has been shown to negatively impact the balance of our gut microbiota.
Evidence from a range of sources is emerging to suggest that people with different mental disorders like depression or anorexia have distinct gut microbiota compositions. For example, studies that transplanted human gut microbiota from depressed patients into germ-free mice repeatedly find the mice become withdrawn and inactive. Researchers also see changes in the biochemistry of the mice brains.