In the first of this two-part blog, Registered Dietitian Laura Tilt looks at the current thinking around IBS and explores the case for using prebiotics as part of an approach to symptom management.

IBS; a global condition

Of all gastrointestinal conditions, irritable bowel syndrome (IBS) is the most commonly diagnosed, and consequently one which healthcare professionals are likely to encounter in their clinical practice. The condition affects around 1 in 10 adults worldwide1, is typically diagnosed in adults under 50, and more commonly in women than men2. Alongside abdominal discomfort, symptoms include a change in stool form or frequency, bloating, wind, nausea and fatigue. For years, IBS was classified as a functional gastrointestinal disorder (FGID) due to the lack of identifiable disease or structural abnormalities associated with the condition. More recently, it has been renamed as a ‘disorder of gut-brain interaction’2,3, emphasising a central role for dysregulation of gut-brain communication in its pathophysiology. In addition, evidence of low-grade inflammation, immune activation and microbiome disruption have been identified2, challenging the long-held belief that structural changes are absent.

Although symptoms fluctuate in severity, IBS is a chronic condition which has a significant impact on quality of life similar to other gastrointestinal diseases. Symptoms can negatively impact on work, relationships and social life1. Studies show patients often reported feeling stigmatised by friends, family and doctors, since a functional diagnosis is sometimes viewed as less legitimate than an organic disease. In one survey of people with IBS, respondents reported that on average they’d be willing to give up 25% of their remaining life (an average of 10-15 years) in order to be symptom free1.

Taking into account it’s chronic debilitating nature and associated healthcare costs (estimated to be somewhere between £45.6-200 million per annum in the UK1) it’s important that individuals with IBS are given appropriate support and clear concise information about the various routes to managing symptoms. In doing so, both patient-clinician relationships and outcomes can be improved. 

Approaches to Symptom Control   

As detailed in the 2008 NICE clinical guidelines for IBS4, therapies for symptom management are focused in three areas - dietary and lifestyle advice, symptom targeted pharmacotherapy (such as laxatives and antispasmodics) and psychological interventions. Dietary changes are typically the first approach that clinicians recommend patients try. This makes sense given that 9 in 10 individuals with IBS report that food aggravates symptoms5, and we know that certain foods or components of food have the potential to trigger symptoms by altering motility, stimulating mechanoreceptors, through malabsorption or interaction with the gut microbiome. General dietary advice for IBS includes guidelines around adjusting alcohol, caffeine, spicy, high fat, high fibre foods and eating patterns5. In addition, patients are encouraged to make time to relax and manage stress levels4.

If symptoms are not improved through basic dietary and lifestyle changes, patients can be referred to a dietitian for a trial of the low FODMAP diet5. This approach involves restricting FODMAPs - a group of short chain carbohydrates found in a wide variety of foods which are poorly absorbed in the small intestine but readily fermented in the colon, triggering symptoms like bloating, discomfort and loose stools in people with IBS. Although the low FODMAP diet has been shown to be very successful (with research showing ~60-75% of patients experience symptom improvement when the diet is delivered by a FODMAP trained dietitian) we know that it’s not a panacea. In addition, only a small number of dietitians are trained to deliver the diet, which limits patient access. It’s important to note too that dietary restriction isn’t always suitable, especially for individuals already following restricted diets or those with a history of disordered eating. In these cases (and those on long wait lists), alternative approaches are worth exploring. 

The Gut Microbiome in IBS

In the last ten years, research into the gut microbiome and its relationship with health and disease has evolved at great speed. In relation to IBS, studies have found differences in the faecal microbiota of those with IBS compared to healthy controls, which may play a role in altered colonic transit and bowel habits in a subset of patients1. Research has also linked reduced gut microbiome diversity with increased symptom severity. Given these findings (and the fact that both FODMAP restriction and reduced fibre intake can further reduce the diversity of the gut microbiome1), there has been a growing interest in whether modulating the gut microbiome may be an effective route to symptom control for some patients. 

Prebiotics and Probiotics as a Therapeutic Strategy

Prebiotics - Substrates that are selectively utilized by host microorganisms conferring a health benefit

Probiotics - Live microorganisms that, when administered in adequate amounts, confer a health benefit on the host

Two low-cost and accessible approaches to modifying the gut microbiome involve the use of prebiotics and probiotics. Whilst some strains of probiotics have been shown to have a positive effect on symptom control (reducing bloating and discomfort), conclusions about their effectiveness have been limited by heterogeneity in study design and interventions (e.g. single strain versus multi strain). Nevertheless, probiotics are considered safe, and the current guidelines for people with IBS are to try a product for 4 weeks at the intake recommended whilst monitoring the effects5.

What about prebiotics?

A newer concept, introduced by Glenn Gibson and Marcel Roberfroid in 1995, prebiotics are substrates (typically carbohydrates) which are not digested, but which selectively feed native beneficial microbes, conferring a health benefit. So, whereas probiotics are live microbes, prebiotics function as a food source for health-promoting microbes.


When consumed in sufficient quantities, prebiotics can help to increase the number of bifidobacteria in the colon, increase faecal short chain fatty acids, and reduce transit time, effects which could theoretically benefit the IBS patient6. So, what does the research say? A recent meta-analysis of prebiotics in functional gut disorders suggests that the effects varied with both the type and quantity of prebiotic consumed6, so what can we recommend? Read part 2 to take a look at the evidence in more detail.

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