Cortisol: The Link Between The Gut And The Brain

Two Way Gut Brain Function

Cortisol is often referred to as the “stress hormone” due to its association with the stress response. Nevertheless, there is more to cortisol than originally thought. A new and exciting area of research has indicated that cortisol could play a fundamental role in interactions between gut bacteria and brain function.

Cortisol is a steroid hormone secreted by the adrenal glands and is controlled by a combination of glands thought the body known as the HPA axis. It is often released in larger quantities during stressful situations and has also been associated with overeating and weight gain. Lifestyle factors like managing stress and eating a healthy balanced diet have been associated with maintaining normal levels of cortisol.

Why is gut health so important?

It has been well established that gut health is important for us to be able to supply our body with required nutrients, as well as protecting us from harmful toxins and pathogens. In recent years, gut microbes and their functions have received a lot of publicity. Further investigation into our gut flora shows that they may well play important roles in our immunity and brain function too.

Cortisol – The mediator between the gut and the brain

New research shows that, as well as human health gut microbes, can influence behaviour and certain neurological disorders e.g. autism. A recent study from the University of Illinois suggests the presence of a pathway of communication between brain metabolites and gut bacteria in which cortisol is involved.

Mudd and his colleagues studied 1-month old piglets to investigate the connection between neurometabolites and microbes in the gut. Piglets are surprisingly similar to human infants in regards to gut and brain development.

At first, the study looked at identifying relationships between the fecal bacteria and brain metabolites of the piglets. Their findings showed a correlation between the bacteria in the genera Bacteroides and Clostridium and the concentration of myoinositol in the brain, as well as links between the bacteria Butyricimonas and compound N-acetylaspartate (NAA).

Another bacteria they investigated, Ruminococcus correlated indirectly with NAA in the brain i.e. the higher the amount of Ruminococcus in the gut, the lower the amounts of NAA in the brain. NAA plays an important role in balancing fluid levels in the brain.

The study then went on to investigate the possible connection between different bacteria and compounds in the blood. The research found that Bacteroides was linked to higher levels of serotonin, whereas Ruminococcus was associated with lower concentrations of serotonin and cortisol. Ruminococcus’s link with both NAA and cortisol, raised the question could there be a mechanistic link between all three?

Analysis of their findings does indeed show a possible relationship whereby serum cortisol mediates the relationship between NAA in the brain and Ruminococcus in the gut.

How will this research improve our understanding how a good diet can improve your brain function?

These findings illustrate the importance of a healthy diet. If the microbes in the gut have the potential to influence brain function, following a healthy diet could help encourage a beneficial balance of gut flora. Therefore, diets could be manipulated to create an optimum balance of gut microbes to help prevent and treat a number of possible health issues from depression to autism.