Stress, the microbiome and IBS

The reclassification of irritable bowel syndrome (IBS) is not so new, but it's pivotal in transforming our understanding of this complex condition, particularly the link between stress, gut health, and the microbiome.

Previously, IBS was diagnosed through exclusion, often leaving people frustrated by vague explanations and no clear physical cause for their symptoms. While it remains important to rule out conditions like Inflammatory Bowel Disease (IBD), there is now far greater awareness of the underlying drivers of IBS, supporting a more holistic and personalised approach to treatment.

What does this mean for you and your IBS?

The gut-brain axis

From a “functional gastrointestinal disorder”, IBS was reclassified by the Rome IV criteria in 2016. IBS had been considered a functional disorder, when it was accepted that no physical structural or metabolic changes could be found. What has now been recognised is that IBS goes beyond a gastrointestinal disorder. It is not just about function in the gut, but also about the interaction between the brain and the gut. IBS is now classified as a “disorder of gut-brain interaction”.

Your gut and your brain are intimately connected, communicating via the gut-brain axis, an intricate network linking emotions and gut function. Communication, orchestrated by the vagus nerve, takes place in both directions: between gut and brain, and between brain and gut. The gut-brain axis is responsible for maintaining balance in gut functions and for linking functions of the gut with functions of the brain. The gut-brain axis coordinates the physical and emotional states of your body.

The role of the gut-brain axis in IBS is now recognised.

An intricate network

One part of the network of the gut-brain axis is the enteric nervous system, which is in charge of basic gut function, the actions that move food and waste through your digestive system. Any disruption to the enteric nervous system has an impact on this process, which may lead to symptoms such as diarrhoea or constipation.

Other parts of the network are the autonomic nervous system and the hypothalamic-pituitary-adrenal (HPA) axis, with key roles in your body’s physiological responses to stress. Stress may cause these parts of the network to be underactive or overactive, which has an impact on the interactions between your gut and brain, affecting your gut function and pain sensation.

The interconnections in the gut-brain axis are affected by your gut function and by your body’s responses to stress. Your emotional state is affected by your gut, and your gut is affected by your emotional state.

Disruption in the interactions of the gut-brain axis is linked to the symptoms of IBS.

A key player: The microbiome

A key player in this network, helping to control the gut-brain axis, is the gut microbiome, creating a microbiome-gut-brain axis. The gut microbiome is home to communities with trillions of diverse microbes. Not only do these microbes depend on humans for their survival, but human survival depends on these microbes.

Some of the microbes are helpful for the human host, and some are harmful. When the harmful microbes thrive and the helpful microbes are overwhelmed, possibly caused by food choices or antibiotics, there is a state of dysbiosis. This disrupts normal function in the gut-brain axis.

When samples from the microbiomes of people with IBS have been analysed, differences have been found in the microbial communities. It is not yet fully clear whether these differences occur before IBS develops, possibly contributing to the development of IBS, or whether these differences occur as a result of IBS. Either way, dysbiosis is implicated in IBS.

Stress

While stress is a normal part of life, everyone’s experience of stress is different. You may experience a particularly stressful life event, or have experienced a traumatic event in the past. Or you may be particularly sensitive to stress. Stress is also a factor in living with IBS.

Stress has an impact on the interactions in your gut-brain axis, leading to changes in your gut sensitivity and function. Stress also causes changes in your microbiome. Stress is known to affect IBS, causing flare-ups and aggravating symptoms.

IBS is recognised as a stress-sensitive condition.

A holistic approach to IBS

Whether you are self-managing your IBS or whether you seek help from a practitioner, a holistic approach, personalised for you, is essential to address both gut health and stress management.

Food

Your food choices are foundational to managing your IBS with confidence. Food is a driving force in your microbiome, and in turn, your microbiome supports your stress management. Everyone is different, and food choices need to be personalised so that they are right for you.

A food diary helps you to identify foods that trigger your symptoms. Common food triggers are fatty foods, which need to be avoided. Caffeine also speeds up gut function, so reducing caffeinated drinks may be recommended.

A food plan helps you put some changes into place. Start by establishing a regular eating pattern with three meals a day, taking time for each meal. Balance your meals with beneficial food choices. Stay well hydrated.

Foods to support your microbiome include prebiotics (such as garlic or banana) and fermented foods (such as authentic sauerkraut or kefir). Only include these foods if you tolerate them well and they do not trigger your symptoms.

Fibre

Fibre is helpful for constipation but not for all types of IBS. Choose soluble fibre (such as oats or psyllium) but not insoluble fibre (such as whole grains).

Probiotics

Probiotics (such as Bifidobacterium and Lactobacillus) help to restore balance in the microbiome. If there is no improvement after a trial of 12 weeks, there is no need to continue with the probiotics.

FODMAP

FODMAP refers to particular types of carbohydrates that are not properly absorbed in the gut, which may cause symptoms for some people with IBS. These include:

• beans and lentils
• dairy
• wheat
• some vegetables, such as onions, garlic, and asparagus
• some fruits, such as apples, cherries, pears, and peaches

A low FODMAP diet may be effective, but it is highly restrictive and needs to be implemented under the guidance of a specialist. It is not recommended in the long term.

Exercise

Although you may not feel like exercising with IBS, low to moderate intensity exercise is unlikely to trigger symptoms and is helpful to manage symptoms and stress. Options include walking, jogging, swimming, yoga, and low-impact aerobics. However, high-intensity exercise (such as running, competitive sports, and high-intensity interval training) may aggravate symptoms and should be avoided.

Relaxation

Techniques to calm your stress responses and support relaxation. Options include mindfulness exercises or structured meditation.

Cognitive behavioural therapy (CBT)

CBT gives you a framework to link your thoughts, actions and emotions, helping you to manage stressful situations with an increased sense of control. IBS-specific CBT may improve gut symptoms, emotional distress and quality of life.

Hypnotherapy

Hypnotherapy induces a deep state of relaxation, using a range of techniques to help you normalise gut function and alleviate pain. Gut-directed hypnotherapy with IBS protocols may be personalised for your specific symptoms.

References

• Berding K., Bastaanssen T.F.S., Monloney G.M. et al (2022) Feed your microbes to deal with stress: a psychobiotic diet impacts microbial stability and perceived stress in a health adult population - https://www.nature.com/articles/s41380-022-01817-y (Accessed 10.7.2025)
• Carabotti M., Scirocco A., Maselli M.A. et al (2014) The gut-brain axis: interactions between enteric microbiota, central and enteric nervous system - https://pmc.ncbi.nlm.nih.gov/articles/PMC4367209/ (Accessed 29.6.2025)
• Chang L. (2011) The role of Stress on Physiological Responses and Clinical Symptoms in Irritable Bowel Syndrome - https://pmc.ncbi.nlm.nih.gov/articles/PMC3039211/ (Accessed 10.7.2025)
• Foster J.A., Rinaman L. & Cryan J.F. (2017) Stress & the gut-brain axis: Regulation by the microbiome - https://www.sciencedirect.com/science/article/pii/S2352289516300509 (Accessed 10.7.2025)
• El-Hakim, Y., Bake, S. Mani, K.K. et al (2021) Impact of intestinal disorders on central and peripheral nervous system diseases - https://pubmed.ncbi.nlm.nih.gov/35032636/ (Accessed 2.7.2025)
• Ghaffari P., Saeed S. & Nielsen K.L. (2022) Irritable bowel syndrome and microbiome; Switching from conventional diagnosis and therapies to personalised interventions - https://translational-medicine.biomedcentral.com/articles/10.1186/s12967-022-03365-z (Accessed 29.6.2025)
• Mayer E.A., Ryu H.J. & Bhatt R.R. (2023) The neurobiology of irritable bowel syndrome - https://pubmed.ncbi.nlm.nih.gov/36732586/ (Accessed 10.7.2025)
• Mayer E.A., Nance K. & Chen S. (2022) The Gut-Brain Axis - https://www.annualreviews.org/docserver/fulltext/med/73/1/annurev-med-042320-014032.pdf?expires=1752589557&id=id&accname=guest&checksum=B66DF87F8CB218E2A7C1C4D112ADD296 (Accessed 10.7.2025)
• Pastras P., Aggeletopoulou I. & Triantos C. (2024) Impact of Enteric Nervous Cells on Irritable Bowel Syndrome: Potential Treatment Options - https://pmc.ncbi.nlm.nih.gov/articles/PMC11510338/ (Accessed 2.7.2025)
• Quin H.-Y., Cheng C.-W., Tang, X.-D. et al (2014) Impact of psychological stress on irritable bowel syndrome - https://pmc.ncbi.nlm.nih.gov/articles/PMC4202343/ (Accessed 10.7.2025)
• Shaikh S.D., Sun N., Canakin A. et al (2023) Irritable Bowel Syndrome and the Gut Microbiome: A Comprehensive Review - https://pmc.ncbi.nlm.nih.gov/articles/PMC10095554/ (Accessed 29.6.2025)
• Vasant D. H., Paine P.A., C.J. Black et al (2021) British Society of Gastroenterology guidelines on the management of irritable bowel syndrome - https://gut.bmj.com/content/gutjnl/70/7/1214.full.pdf (Accessed 29.6.2025)
• York and Scarborough Teaching Hospitals (2022) Irritable Bowel Syndrome (IBS) - https://www.yorkhospitals.nhs.uk/seecmsfile/?id=6880 (Accessed 29.6.2025)