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What is the Vagus Nerve and how does it relate to IBS?

Updated: Jan 3

If you struggle with digestive pain and discomfort, depression, or anxiety related to irritable bowel syndrome (IBS) then you might want to look at increasing or improving your vagal tone.

What is vagal tone?

Vagal tone is the degree of activity happening within the parasympathetic nervous system, helping our bodily systems to self-regulate, which can result in reduced inflammation, and improved cardiovascular, endocrine (hormones), and immune markers (1). The vagus nerve also contributes to the bi-directional interactions between the gut and the brain, otherwise known as the gut-brain axis (2).

Low vagal tone is when the vagus nerve isn’t working as it should, and this can lead to anxiety, depression, digestive problems, as well as systemic inflammation.

Stress and Cortisol

It is widely understood that stress can exert huge negative consequences on our personal and professional lives, and too much stress can be extremely detrimental to our health. Cortisol, which is a stress hormone produced by the adrenal glands, is a significant driver in most chronic health and disease processes (3).

Irritable bowel syndrome is a functional gastrointestinal disorder characterised by disturbed bowel movements (either constipation and/or diarrhoea), and persistent chronic abdominal pain. Whilst it is primarily a digestive system disorder, the studies have also associated it as a psychosomatic disorder, which is exacerbated by stressful situations (4).

Research show significant increases in morning cortisol in people with both IBS and depression (5). Those individuals with IBS who were experiencing prolonged stress were more likely to show high cortisol levels (4).

At times, a certain amount of stress can be beneficial, to help us meet deadlines and pass tests (6). And we need a certain amount of cortisol for our immunity, our blood glucose regulation, as well as our diurnal rhythm, however, it is necessary that we don’t overtax this system, as high cortisol can become inflammatory when released excessively (7).

There has been a large amount of recent interest in the role of the parasympathetic nervous system as a way to help us to unwind and relax, and ultimately to decrease our cortisol levels. The vagus nerve is the main component of the parasympathetic nervous system and is involved in relaxing the body (8).

Where does the vagus nerve fit into the human nervous system?

The vagus nerve, also known as the "wandering nerve", is the tenth cranial nerve, originating in the brainstem and travelling all the way to the gut, connecting it to the central nervous system. Its' main function is to send nerve signals between the gut and the brain. It is the longest nerve of the autonomic nervous system. The nervous system has two main parts, the central nervous system (CNS), and the peripheral nervous system (PNS).

The central nervous system consists primarily of the brain and the spinal cord. The peripheral nervous system consists of the somatic nervous system, responsible for voluntary or conscious muscular functions, and the autonomic nervous system, which is unconsciously controlled.

The autonomic nervous system is divided again into two parts, the sympathetic nervous system and the parasympathetic nervous system.

The Sympathetic Nervous System

When the Sympathetic nervous system is activated, it is known as our “fight or flight” response. This is the initial response that causes the adrenal glands (located just above the kidneys) to secrete cortisol and adrenalin, both stress hormones. Cortisol is important for our immunity and for controlling our blood sugar balance, as well as our gut health, and helping us to deal with stress.

Our ancient predecessors used this “fight or flight response” to help them to deal with a perceived threat or danger, such as running from a wild animal. The ‘emergency’ would soon be over with and they could return to their daily chores in a more relaxed pace. However, in modern times, this fight or flight response can often be over-activated due to a variety of reasons including high-pressure work environments, a stressful home life, fast-paced lifestyles, toxins, heavily processed and rich foods, as well as excessive caffeine and alcohol consumption, all causing stress on the body, and increased circulating cortisol.

Physiologically, when we are in “fight or flight” our body’s ability to digest our food is greatly hindered. Our digestive system is suspended during stress, meaning that the body shuts down the production of enzymes required for digestion, also inhibiting the production of stomach acid. Stomach acid (hydrochloric acid) is required to breakdown or metabolise our proteins, which, when undigested, can cause bloating and digestive discomfort.

Furthermore, high cortisol reduces Secretory IgA (SIgA), part of the innate immune system. Low SIgA can lead to the proliferation of pathogenic bacteria in the gut, which in turn has the potential to lead to food intolerances, Irritable Bowel Syndrome (IBS), intestinal permeability, and potentially autoimmune disease if unresolved (9).

Serotonin receptors in the gut may be affected due to hypothalamic-pituitary-adrenal axis (HPA axis) dysregulation, which may also have an effect on gut motility and mood issues such as anxiety and depression, often correlated with IBS.

While cortisol is an important part of the body's stress response, it is also important that the "fight or flight" system returns to normal.

The Parasympathetic Nervous System

The parasympathetic nervous system, also known as “rest and digest”, is the part of the autonomic nervous system that facilitates our digestion and heart rate.

The vagus nerve is the primary component of the parasympathetic nervous system, and plays a key role in our cardiovascular health, respiratory system, gastrointestinal system, immunity, detoxification, and many other bodily functions, including sweating, swallowing, and speech.

Increased vagal tone helps to suppress inflammation, supports immune resilience, and greater stress resistance while helping to control anxiety and depression, with a beneficial impact on IBS.

Decreased vagal tone is associated with poor digestion due to delayed gastric emptying (gastroparesis) and poor gut motility, elevated blood pressure, increased heart rate, cognitive impairment, and heightened stress response.

We need to be doing more restful and calming activities to help activate this system more often.

How does it relate to IBS?

The parasympathetic fibres of the vagus nerve connect to all of our internal organs from the neck down (excluding the adrenal glands), playing a key role in critical bodily systems such as our heart rate, breathing, sweating, detoxification, muscle response, and specifically for IBS, gastrointestinal peristalsis, or the contraction and movement of the faeces through the intestines.

The microbiome-gut-brain axis is a bi-directional communication system that relies on the parasympathetic nervous system, specifically the vagus nerve, to transfer information from the gut to the central nervous system (i.e. the brain).

If you struggle with digestive symptoms associated with IBS, inflammatory bowel disease (IBD), small intestinal bacterial overgrowth (SIBO), or gastroesophageal reflux disease (GERD), such as flatulence, bloating constipation, diarrhoea, or acid reflux, it’s important to activate your vagus nerve regularly.

What can we do to improve our vagal tone?

There are many ways that we can increase our vagal tone, and some of them include:

Yoga and Meditation

Adopting a daily practice of meditation and yoga stimulates the vagus nerve, reducing stress and anxiety, while also increasing GABA production, a neurotransmitter in the brain which helps us to relax. An increase in vagal tone from mindfulness-based stress reduction techniques such as yoga and meditation have been shown to reduce anxiety and depression, as well as post-traumatic stress disorder, PTSD (10).


Diaphragmatic breathing (or slow abdominal breathing) instantly stimulates the vagus nerve and lowers our stress response (11). Rebirthing and Holotropic Breathwork are great ways to get started. There are also FREE apps available to help with this practice, such as Flourish by the Breath Guy ( and this guided Wim Hof Method Breathing video.

Cold water therapy

Medication-resistant major depressive disorder and anxiety have shown a sustained reduction in symptoms when adopting daily open water swimming (12). Taking a cold shower or plunging into ice-cold water is known to improve vagal tone, also reputed to enhance circulation, assist with weight loss, and reduce muscle inflammation. Cold water immersion is promoted by Wim Hof.

See for more information on how to incorporate this safely.

Singing and chanting

Singing, humming, chanting, and/or gargling stimulates the vagus nerve as it activates the muscles and vocal cords at the back of the throat, which are connected to the nerve. Singing has been related to many physiological benefits including enhanced immune function, and increased feelings of happiness (13).

Some other ways to improve vagal tone include eating an anti-inflammatory diet, massage, reiki, acupuncture, forest bathing, engaging in hobbies, listening to music, socialising, and laughing.

Consider purchasing a copy of my cookbook for anti-inflammatory recipes:

Helen Ross is a Registered Nutritionist ® specialising in gut health and IBS support. If you'd like to know more about eating for a healthy gut, and/or how to keep your gut healthy, book in for a FREE call here to discover how she can help you.

Helen offers a virtual (online) clinic as well as local IBS support and nutritional therapy services to the Bridport, Dorchester, Weymouth, Poole, Bournemouth, and East Devon areas.

My Simple Gut ReSet is designed to help us get to the root cause or causes of your health issues. The aim is to nourish and support the gut lining to assist it back to a healthy state. A robust intestinal lining is an essential first step for finding freedom from painful, frustrating and embarrassing symptoms of IBS and other gut-related symptoms and health problems.

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'10 Ways to Assist the Digestive Process' and 'Causes of IBS and Natural Ways to find Relief from your Symptoms'

For more information see:


1. Weber, C. S. et al. (2010) ‘Low vagal tone is associated with impaired post stress recovery of cardiovascular, endocrine, and immune markers’, European Journal of Applied Physiology. doi: 10.1007/s00421-009-1341-x.

2. Bonaz, B., Sinniger, V. and Pellissier, S. (2016) ‘Vagal tone: Effects on sensitivity, motility, and inflammation’, Neurogastroenterology and Motility. doi: 10.1111/nmo.12817.

3. Lee, D. Y., Kim, E. and Choi, M. H. (2015) ‘Technical and clinical aspects of cortisol as a biochemical marker of chronic stress’, BMB Reports. doi: 10.5483/BMBRep.2015.48.4.275.

4. Sugaya, N. et al. (2015) ‘Effect of prolonged stress on the adrenal hormones of individuals with irritable bowel syndrome’, BioPsychoSocial Medicine. doi: 10.1186/s13030-015-0031-7.

5. Hritcu, L. D. et al. (2019) ‘Serum cortisol levels modifications in patients with depression and irritable bowel syndrome’, Revista de Chimie. doi: 10.37358/rc.19.9.7554.

6. Lee, D. Y., Kim, E. and Choi, M. H. (2015) ‘Technical and clinical aspects of cortisol as a biochemical marker of chronic stress’, BMB Reports. doi: 10.5483/BMBRep.2015.48.4.275.

7. Herriot, H. et al. (2017) ‘Intra-individual cortisol variability and low-grade inflammation over 10 years in older adults’, Psychoneuroendocrinology. doi: 10.1016/j.psyneuen.2016.12.010.

8. Pellissier, S. et al. (2014) ‘Relationship between Vagal Tone, Cortisol, TNF-alpha, epinephrine and negative affects in Crohn’s disease and irritable bowel syndrome’, PLoS ONE. doi: 10.1371/journal.pone.0105328

9. Pigrau, M. et al. (2016) ‘The joint power of sex and stress to modulate brain-gut-microbiota axis and intestinal barrier homeostasis: Implications for irritable bowel syndrome’, Neurogastroenterology and Motility. doi: 10.1111/nmo.12717.

10. Breit, S. et al. (2018) ‘Vagus nerve as modulator of the brain-gut axis in psychiatric and inflammatory disorders’, Frontiers in Psychiatry. doi: 10.3389/fpsyt.2018.00044.

11. Aideyan, B., Martin, G. C. and Beeson, E. T. (2020) ‘A Practitioner’s Guide to Breathwork in Clinical Mental Health Counseling’, Journal of Mental Health Counseling. doi: 10.17744/mehc.42.1.06.

12. Van Tulleken, C. et al. (2018) ‘Open water swimming as a treatment for major depressive disorder’, BMJ Case Reports. doi: 10.1136/bcr-2018-225007.

13. Kang, J., Scholp, A. and Jiang, J. J. (2018) ‘A Review of the Physiological Effects and Mechanisms of Singing’, Journal of Voice. doi: 10.1016/j.jvoice.2017.07.008.

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