IBS: a disorder of the gut-brain axis.
IBS or Irritable Bowel Syndrome is an umbrella term used to describe undesirable gut symptoms including chronic or recurrent abdominal pain and altered bowel habits (change in stool frequency and consistency). It is often a multifactorial condition, and as such, the underlying cause(s) can be difficult to pin down.
What are some of the underlying causes?
Altered brain function – brain imaging studies have shown that structural and functional changes can be seen in the brain networks of IBS patients
Altered gut motility – IBS can either be characterised by constipation, diarrhoea or alternating constipation and diarrhoea
Altered gut sensitivity – an increased sensitivity to pressure and/or gut discomfort is common to many IBS sufferers. This may be due to an increased amount of gut nerve fibres
Altered gut barrier function – there is evidence to show that IBS patients tend to have issues with intestinal barrier function, sometimes referred to as ‘leaky gut’
Altered immune function – IBS sufferers often have increased immune activation and a higher number of pro-inflammatory immune cells
Altered gut microbiota – typically individuals with IBS have reduced microbial diversity and/or lack certain strains of beneficial bacteria, such as Bifidobacterium
Dysregulated stress response – stress management is very important in resolving IBS
Although there are several different mechanisms which can trigger IBS symptoms, all of the above are gut-brain axis alterations. Research points towards a role for the gut-brain axis in both IBS and mood disorders. There is a high level of comorbidity between IBS and mood disorders - approximately 44% and 25% of IBS patients presenting at gastroenterology clinics also suffer from anxiety and depression, respectively. It is estimated that individuals with IBS are three times more likely to have anxiety or depression compared to healthy subjects.
The way the gut, brain and microbiota interact with one another is an incredibly complex system which utilises a number of different signalling pathways including nerve, hormone, immune and microbial signalling. Changes to these communication routes may be central to the development of IBS and mood disorders, whilst alterations in the composition and function of the gut microbiota have been reported in IBS, anxiety and depression.
Probiotics are live bacteria that, when consumed in sufficient amounts, have a beneficial effect on the subject. They work on the gut-brain axis in a number of different ways – by inhibiting potentially harmful bacteria, modulating the immune system and supporting gut barrier function. There is good evidence to suggest that regularly consuming probiotics may be an effective strategy to improve both gut health and mental health.
I often recommend eating a variety of fermented foods of all types to my clients, including one or two portions of yogurt with live cultures, unpasteurised sauerkraut and kimchi on a daily basis. You may also wish to supplement with multi-strain probiotic as well.
Studies have shown that probiotic supplements can take up to 8 weeks to take effect, with the most significant improvements in IBS symptom severity, bowel movements and quality of life scores coming after 12 – 16 weeks. I usually suggest monitoring the effects of probiotics over 3 months.
Another way of effectively strengthening the gut-brain axis is to eat mindfully. Digestions starts in the mouth when we chew our food, and we need to activate the "rest and digest" part of our nervous system to digest our food as well as possible. For this reason, I tell my clients to avoid eating when stressed, distracted or on the go. Ideally, eating should only happen when you are relaxed and sat at a table in an upright position.
My advice would be to take 3 deep belly breaths before each meal to tap into "rest and digest" mode. In addition, savouring the smells and colours of your food activates the brain to send signals to your gut that food is coming and to release enzymes needed to break down that food.
Make sure you chew your food thoroughly (aim for 20 – 30 chews per mouthful) to mechanically break down your food and to allow your saliva to mix well with your meal so it's enzymes can work.
Based on what we now know about the gut-brain-microbiota interactions, fasting may have a profound effect on the composition and function of the gut microbiota. It will also give your digestive system some much needed downtime and allow it to process your food more effectively.
If you want to give intermittent fasting a try, start with a 12 hour overnight fast and gradually increase the length of time you go without food up to a maximum of 16 hours.
References
Dale, H.F., Rasmussen, S.H., Asiller, O.O. and Lied, G.A., 2019. Probiotics in Irritable Bowel Syndrome: An Up-to-Date Systematic Review. Nutrients, 11, p 2048.
Ishaque, S.M., Khosruzzaman, S.M., Ahmed, D.S. and San, M.P., 2018. A randomized placebo-controlled clinical trial of a multi-strain probiotic formulation (Bio-Kult®) in the management of diarrhoea predominant irritable bowel syndrome. BMC Gastroenterology, 18, p71.
Wastyk, H.C., Fragiadakis, G.K., Perelman, D. et al., 2021. Gut-microbiota-targeted diets modulate human immune status. Cell, 184, p 1- 17.
Wilmes, L., Collins, J.M., O'Riordan, K.J. et al., 2021. Of bowels, brain and behaviour: A role for the gut microbiota in psychiatric comorbidities in irritable bowel syndrome. Neurogastroenterology & Motility, 33, e14095.
Zamari, M., Alizadeh-Tabari, S. and Zamari, V, 2019. Systematic review with meta‐analysis: the prevalence of anxiety and depression in patients with irritable bowel syndrome. Alimentary Pharmacology & Therapeutics, 00, p 1-12.
