By Dr Duane Mellor RD PhD

Our mind in our stomach – how the gut and what we eat can influence the brain

Our stomach, or more precisely our gastrointestinal (GI) tract is a complex linked system of organs from our mouth, to our anus. These different organs all with different but complementary jobs, work together, to digest, move and absorb nutrients to keep us both health and happy. To allow this to happen, it is controlled by a range of hormones and nerves. To be able to do this it has developed in a way so that it has its own nervous system. With some scientists suggesting it is almost an independent system working inside us and with us. When this works well and normally, these ‘pace maker’ cells that line it from top literally to bottom, help to keep a regular rhythm so food can make its steady journey and be effectively broken up and digested. However, it can also go wrong, a simple example being when we are nervous, we can get butterflies in our stomach which can affect our appetite. In more severe cases this can impact our health in the form of Irritable Bowel Syndrome and even gastroparesis.

The interaction between our gut and our brain can impact on our health in a number of ways. At its simplest shown by how we experience a nervous tummy, there is clearly a link between our mind, brain and gut. This connection is often called the gut-brain axis, where around half a billion nerves in your GI tract connect to your brain. One of the key nerves which can respond to stress signals is known as the vagal nerve, which allows two way communication between our gut and our brain as part of the parasympathetic nervous system which is part of the half of our nervous system responsible for the involuntary day to day running of our bodies. This part of the nervous system typically is to help our gastrointestinal system make the enzymes and hormones it needs to digest our food, basically work better.  The vagal nerve has also been linked to supporting the healthy functioning of the immune system in our intestine, so may be essential in maintaining the health of not only our digestion but also our whole body too, including possibly our mental health!

Gut, Nerves and Mental Health

This role of the nervous system and especially the vagal nerve can be seen in a range of gastrointestinal disorders and illnesses, as well as is the science is correct, potentially some mental health issues too; including depression. It has been known for a while that lower activity of this part of the nervous system has been observed in people with bowel disease. However, science is starting to reveal that messages from our gut to our brain, transported by this nerve may be partly responsible for alterations in mood. So, keeping our gut, and the nerves supplying them well, might have a role in maintaining our overall health too!

What is especially interesting is looking at how this may be affected by food and potentially supplements. It has been shown that a healthy Mediterranean Diet may not only keep our bowels healthy by eating plenty of fresh vegetables, fruits as well as fibre from wholegrains, nuts, pulses and seeds, it can also improve mental health. A study investigating the effects of fish oil along with a Mediterranean diet found the better the person’s diet scored relative to the ideal Mediterranean diet was associated with a lower depression score. This has also been looked at in laboratory experiments with animals, to look at the effect of probiotic supplements, which have been shown to help the functioning of the vagal nerve and were linked to lower stress levels in animals. This has been trialled in people too, with some positive effects on reducing depression scores, but not anxiety is small clinical trials of probiotics.

So, although the scientific evidence is still being uncovered, what appears to be happening is that the health of our gut, including the bacteria living in it, can through the millions of nerves communicating with it, feedback to our brains. So, we need to keep all these parts healthy to enjoy the best possible physical and mental health, this includes being physically active, eating a healthy diet and looking after not just our health, but the health of the bacteria living inside us.