The Gut-Brain Connection


Did you know that Irritable Bowel Syndrome (IBS) has been reclassified from a “functional gut disorder” to a “disorder in the gut-brain interaction”?  Have you also heard that often we don’t need to change our diet at all in order to get on top of IBS symptoms, but instead to focus on non-diet strategies? This article will help you understand more about the gut-brain connection, and its crucial role in our digestion. 

The science 

There is a powerful and constant communication between the gut and the brain via millions of nerves. This can trigger feelings such as ‘butterflies in the stomach’, or a ‘gut feeling’ about something. 

If we’re stressed or anxious, our sympathetic nervous system is activated and the body is in “fight or flight” state. This sends stress signals to the gut whilst the body also redirects blood flow away from the gut (ready to fight or take flight, and thereby pausing digestion). This can negatively affect gut motility which can lead to altered bowel habits and other unwanted digestive symptoms. Essentially, mental stress can create physical stress in our intestine. 

The vagus nerve is the main component of our parasympathetic nervous system, and it is this which is inhibited when the body is in a state of fight or flight. When not stressed, the vagus nerve can send signals that increase digestion, slow the heart and breathing rates, and get the body into “rest and digest” mode. 

What is really interesting, is that not only can we improve our digestive symptoms through targeting this gut-brain connection, but studies have shown that due to the 2-way nature of the interaction between the gut and brain, we can also improve our mental health by targeting what goes into our digestive system. The ‘SMILES’ trial in 2017 found that when participants with diagnosed depression increased their intake of plant-based foods (such as fruit, vegetables, wholegrains, legumes, nuts and seeds) as well as fish and healthy fats, alongside reducing their intake of convenience or highly processed foods, they were 4x more likely to improve their depression scores vs counselling alone. Our gut microbiome (the trillions of microbes in our gut) has a key role in this mechanism. 

Comparing diet to non-diet therapies

When considering how to treat IBS and other digestive symptoms, we know that short-term changes can be effective at reducing the hypersensitivity in our bowel. However, if we’re not looking at the whole picture, and considering activity levels, sleep quality, and mental stressors then we’re unlikely to get symptom resolution for the longer term. 

High quality scientific studies have shown that non-diet approaches such as cognitive behavioural therapy (CBT), relaxation techniques, gut-directed hypnotherapy and yoga can be just as effective as the low FODMAP diet which is the evidence-based dietary treatment to IBS. This is pretty incredible, because it means that without restricting food, you can treat the underlying cause of the dysfunction between the gut and the brain via the vagus nerve. 

These non-diet approaches take longer to see results – we recommend persevering with this route for at least 12 weeks. 

Let’s take a look at each of the options for targeting the gut-brain connection in a little more detail:

– Gut-Directed Cognitive-behavioural therapy (CBT)

CBT for IBS won’t be the same as general CBT. Suitably qualified therapists use a specially designed protocol that improves and regulates the gut-brain interactions. These can be delivered in individual or group sessions that may be in-person, online or over the phone. 

CBT for IBS has been well researched. A systematic review in 2020 documented that CBT has consistently shown to be effective for achieving significant and long-lasting improvements on IBS symptoms and quality of life. 

– Gut-Directed Hypnotherapy (GDH)

GDH differs from psychological therapies like CBT which are aimed at the conscious mind. GDH instead aims to improve the gut-brain connection by getting the patient into a deeply relaxed state, and then using visualisation exercises (e.g. your gut is a free-flowing river) followed by  specific gut-related suggestions and therapeutic directive phrases for the subconscious to absorb and act upon. You retain full control of your body and mind at this time. 

Scientific research has shown that GDH can be effective for 70-80% of IBS patients at improving gastrointestinal symptoms (such as abdominal pain, bloating, diarrhoea, and constipation) as well as reducing feelings of anxiety or depression. 

GDH can be delivered via a suitably qualified therapist who can provide 1:1 sessions. You can also access GDH via a mobile app called Nerva which is based on research by Monash University . 

– Yoga

The practice of yoga involves physical poses, concentration, and deep breathing. Scientific research has found that yoga is not only beneficial in the context of IBS, but it also has other health benefits including reducing inflammation and improving mental health. Interestingly, one study in 2018 compared yoga to the low FODMAP diet and found that it had equal benefits, with over 80% reporting significant improvements in their IBS symptoms. 

The physical movements of yoga help soothe the muscles and nerves in the intestine. Poses such as happy baby, child’s pose, and some simple led down twists can all be beneficial to include in a routine. But it’s the breathwork during a yoga practice which is what activates the parasympathetic nervous system (and gets us into “rest and digest” mode). 

– Heart-rate Variability (HRV)

HRV is a measure of naturally occurring beat to beat changes in our heart rate. Variability or irregularity in our heart rhythms can be quite normal. However, too much instability can be detrimental to our physiological functioning. The heart actually sends more signals to the brain than the brain sends to the heart. As the brain is also in constant communication with the gut, studies suggest that consideration of HRV can have a positive effect on gut function and symptoms. 

A systematic review in 2022 suggested that HRV measurements should be used to assess autonomic nervous system changes during IBS therapy. In other words, getting us from fight or flight into rest and digest as often as possible. 

There are practitioners who offer HRV focussed IBS therapy, where patients use simple strategies and techniques to improve their heart rhythms. This gets their body into the optimal state for the most beneficial functioning of the nervous system, which in turn has a positive impact on gastrointestinal symptoms and psychological well-being.


IBS isn’t just about diet. It’s important to take a holistic approach which considers diet, sleep, exercise and other lifestyle factors and stressors.

For a large number of individuals, simple dietary and lifestyle techniques can get on top of their digestive symptoms. However, especially where individuals acknowledge that stress or worry is a key driver of symptoms, a gut-targeted psychological intervention (one that focuses on the gut-brain connection) is hugely beneficial. 

I am a dietitian and not a psychologist! In certain circumstances I refer or recommend my clients to other healthcare professionals who specialise in the above non-diet treatment methods. I have completed the Nerva IBS Clinician’s Course which enables me to discuss the hypnotherapy treatment for IBS in great detail with my clients as well as provide them with a discount off the course.

Get in touch today if you’re keen to learn more.  


Jacka, F.N., O’Neil, A., Opie, R. et al. A randomised controlled trial of dietary improvement for adults with major depression (the ‘SMILES’ trial). BMC Med 15, 23 (2017). https://doi.org/10.1186/s12916-017-0791-y 

Manning LP, Yao CK, Biesiekierski JR. Therapy of IBS: Is a Low FODMAP Diet the Answer?. Front Psychiatry. 2020;11:865. Published 2020 Aug 31. doi:10.3389/fpsyt.2020.00865 

van Lanen AS, de Bree A, Greyling A. Efficacy of a low-FODMAP diet in adult irritable bowel syndrome: a systematic review and meta-analysis [published correction appears in Eur J Nutr. 2021 Jun 28;:]. Eur J Nutr. 2021;60(6):3505-3522. doi:10.1007/s00394-020-02473-0 

Everitt HA, Landau S, O’Reilly G, et al. Cognitive behavioural therapy for irritable bowel syndrome: 24-month follow-up of participants in the ACTIB randomised trial. Lancet Gastroenterol Hepatol. 2019;4(11):863-872. doi:10.1016/S2468-1253(19)30243-2

Peters SL, Yao CK, Philpott H, Yelland GW, Muir JG, Gibson PR. Randomised clinical trial: the efficacy of gut-directed hypnotherapy is similar to that of the low FODMAP diet for the treatment of irritable bowel syndrome. Aliment Pharmacol Ther. 2016;44(5):447-459. doi:10.1111/apt.13706

D’Silva A, Marshall DA, Vallance JK, et al. Meditation and Yoga for Irritable Bowel Syndrome: A Randomized Clinical Trial [published online ahead of print, 2022 Nov 25]. Am J Gastroenterol. 2022;10.14309/ajg.0000000000002052. doi:10.14309/ajg.0000000000002052

Schumann D, Langhorst J, Dobos G, Cramer H. Randomised clinical trial: yoga vs a low-FODMAP diet in patients with irritable bowel syndrome. Aliment Pharmacol Ther. 2018;47(2):203-211. doi:10.1111/apt.14400

Polster A, Friberg P, Gunterberg V, et al. Heart rate variability characteristics of patients with irritable bowel syndrome and associations with symptoms. Neurogastroenterol Motil. 2018;30(7):e13320. doi:10.1111/nmo.13320

Mróz M, Czub M, Brytek-Matera A. Heart Rate Variability-An Index of the Efficacy of Complementary Therapies in Irritable Bowel Syndrome: A Systematic Review. Nutrients. 2022;14(16):3447. Published 2022 Aug 22. doi:10.3390/nu14163447

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Relieve Your Digestive Symptoms

Is IBS holding you down?
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Book a Discovery Call

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