Now you may have heard about the gut-brain axis and how the state of the gut can affect our mood and even our susceptibility to mood disorders like depression and anxiety. Well, let’s talk about the links between the gut and conditions like depression and anxiety.

We tend to compartmentalise the body quite a bit in science, but the gastrointestinal system is so much more than just the part of the body that processes food, extracting that good stuff and storing the rest ready for dumping.

The gastrointestinal system supports a large network of nerves, around 200 – 600 million, that are embedded in the lining that runs the length of the gut – from oesophagus to anus. This network of nerves carries orders from the brain to the various parts of the digestive system. But the communication goes both ways with messages being sent to regions of the brain that process emotion, motivation and memory to name a few.

You’re probably all too aware and of how emotions can affect how your gut behaviours. Remember your last big presentation or seeing the love of your life? The feelings of nausea and the butterflies – that right there is the result of your brain communicating with your gut. And it’s this interaction, between the brain and gut, that is often described as the gut-brain axis.

There are lots of studies exploring how the gut-brain axis influences how parts of the body functions as well as how imbalances in the axis can cause various diseases ranging from Crohn’s disease and IBS (irritable bowel syndrome) to autism spectrum disorders (ASD) and depression.

In addition, large proportions of people with certain psychiatric symptoms and gut disorders, can in point, one study found that 60% of IBS sufferers also had depression. Unfortunately the one thing these studies can’t give us is directionality…which came first the IBS or depression. But what they do highlight is  the importance of a well functioning gut-brain axis and how addressing certain leverage points can rectify imbalances.

For example we know that signalling chemicals or neurotransmitters like serotonin and dopamine play a key role in regulating the gut-brain axis. Serotonin, for instance regulates a number of complex functions including body temperature control and emotions. It is the body’s mood stabilizer. Most of the serotonin in the body is manufactured in the gut and the gut microbiota regulates how this important chemical is produced. It therefore stands to reason that any imbalance in the gut could result in a deterioration in brain function, such as those involved in mood, sleep and behaviour.

Just like the nerves that form the gut-brain axis, different microbiota compositions also have a bi-directional effect on mood disorders, with these various compositions changing the symptoms of mood disorders, while having a mood disorder itself can change the composition of the microbiota. In fact, emotions like anger, fear and sadnees have also been shown to affect the growth of different bacterial species. Studies based on animals that show the use of prebiotics, probiotic and suitable antibiotics can relieve depression and anxiety symptoms suggest potential alternative treatment options, although of course animals studies don’t necessarily translate exactly to humans.

But where the science is available for humans prebiotics have been proven to have a relationship with mood disorders. So what are these prebiotics? Prebiotics are fiber-rich foods that the good bacteria feed and grow on. When the bacteria feed on these foods they produce butyric acid which helps fuels the cells of the large intestines and provides an acidic environment with will make it harder for harmful bacteria to survive. Prebiotics include garlic, Jerusalem artichoke and leeks.

So there you have process by which troubled gut may be sending the signals via the gut-brain axis that trigger negative changes in moods.