Anxiety and the Gut

Anxiety levels are at an all-time high – according to the Mental Health Foundation 22% of women and 15% of men feel anxious all or most of the time.

There are many reasons for our rising anxiety levels; the increasing pressures of modern life, genetics, diet and trauma can all play a role. But scientists are becoming increasingly interested in how the health of our gut can impact our mental health.

You probably know this already, but your gut is kind of a big deal. There are more bacteria in your gut than cells in your body, altogether weighing around 2kg – which is roughly the same weight as your brain by the way! There are 100 million neurones (the same as is it a cats brain, apparently) in your gut, interacting with your gut bacteria and sending messages to and from the brain. It’s no wonder things can go awry in there. It makes sense that if things are out of balance in our gut, that the effect could transfer to our nervous systems and therefore our mental wellbeing.

So if the digestive system and the brain are connected – how can we improve our anxiety levels through the gut?

Most of us have tried to tone our muscles at some point or another, but have you ever thought of toning your vagus nerve? One way that we can reduce our anxiety levels is to stimulate (AKA tone) the nerve that connects our gut and our brain and sends messages between the two. This nerve is responsible for the ‘rest and digest’ mode of our nervous system – the parasympathetic nervous system. It’s the opposite of fight or flight when we’re full of adrenaline and nervous energy. When the parasympathetic nervous system is active, our bodies are geared up to relax, heal and digest our food. The more we stimulate our vagal nerve, the more chilled out and relaxed we become.

The NHS sometimes use a technique where they implant a device that stimulates the vagal nerve into people with severely low mood, and it has been proven to be quite useful for lifting severe depression due it’s calming effects.

However, you don’t have to have anything implanted into you to get the benefits of this. Gut bacteria directly stimulate the vagus nerve and send messages along it, activating the parasympathetic nervous system and as a result, calming us down. It’s thought that ensuring your gut bacteria are healthy, will give you the best chance of stimulating your vagal nerve in the right way.

Another exciting avenue of research is how our gut bacteria impacts our serotonin levels. Serotonin is a neurotransmitter – sometimes dubbed the ‘happy hormone’ – which is thought to improve our mood and calm us down.

Scientists have suggested that more than 90% of our serotonin is synthesised in the gut – with the help of our gut bacteria. A study on mice found that blood levels of serotonin were much lower in mice without gut bacteria (so-called germ-free mice) compared with those with healthy gut bacteria.

When doctors prescribe antidepressant medication (SSRIs) for anxiety, they are designed to help to increase levels of serotonin in the brain. Having healthy gut bacteria that are producing plenty of serotonin provides a natural way to keep our serotonin levels in check. It could also help to explain why taking bacteria from a depressed person and implanting it into a rat, will cause the rat to show depressive behaviours themselves.

Currently, most of the studies done into anxiety and our gut bacteria are carried out on animals; however, the results are compelling. A 2004 study found that giving probiotic bacteria to mice decreased their anxiety levels. While a 2017 study found that mice raised without gut bacteria were found to display an increase in anxiety-like behaviour. This study found that gut bacteria had an impact on molecules called miRNAs in the amygdala – the part of the brain responsible for the fight or flight response which is often very active when we’re anxious. MiRNAs are molecules which control how genes are expressed, and the researchers believe this is one way that our gut bacteria can affect our mental health.

The evidence around gut health and anxiety will continue to emerge but until then doing what you can to promote a healthy digestive system could have a positive impact on your stress and anxiety levels.

Chloe Brotheridge is a hypnotherapist, anxiety expert and author of The Anxiety Solution: a Quieter Mind, a Calmer You. Get a FREE relaxation MP3 when you visit

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