Irritable bowel syndrome and the low FODMAP Diet

MaireadBy Mairéad Keegan

Senior Specialiast Dietitan, NHS Lanarkshire

As a Dietitian, I regularly see patients with irritable bowel syndrome (IBS). People often wonder what exactly IBS is and whether the symptoms as ‘bad’ as patients say? Firstly, let’s look at some of the basic facts before we explore the symptoms:

  • IBS is a chronic and debilitating, functional, gastrointestinal disorder
  • It affects 10-15% of the population, with nearly twice as many women than men being affected
  • It costs the NHS £45.6 million per annum to treat, so potentially reviewing our treatment approach for this cohort of patients, could save the NHS millions of pounds (1,2)
  • Dietitians are extremely well placed to deliver this treatment(3)

So, going back to the initial question: ‘are symptoms as bad as patients say?’ Well, the answer is yes. For some patients, symptoms include: diarrhoea; constipation; bloating; pain; wind; lethargy and nausea. In some cases, symptoms are severe, resulting in numerous medical investigations, reliance on medications for symptom relief and repeated visits to GP’s in primary care or gastroenterologists in secondary care. For others, symptoms may result in unnecessary dietary restrictions and nutritional inadequacies in the diet, reduced quality of life and social isolation. Many patients I have seen reported that they felt their treatment journey was like a ‘revolving door’ with no exit in sight.

As a clinician, there was a point in my career when I felt disheartened and ineffective, when treating patients with IBS. It appeared we could never fully help our patients with symptom resolution or control. Although some did improve with first line National Institute for Health and Care Excellence dietary advice, the majority of patients were discharged with slight, but rarely significant, symptom improvement.

However, all hope was not lost; in February 2012 I finished my training on the low FODMAP diet. The low FODMAP diet has revolutionised the dietetic input for managing patients with IBS. Put another way: FODMAP treatment could be compared to the ‘holy grail’ when it comes to treating patients with IBS. However, before we delve any deeper into this area, let’s take a look at what FODMAPs are.

FODMAP is an acronym for Fermentable, Oligosacchardies, Disaccharides, Monosaccharides And Polyols – all of which are short chain carbohydrates. FODMAPs do not cause the underlying, functional, gastrointestinal disorder that is IBS; but their dietary management offers an opportunity to reduce symptoms. FODMAPs are poorly absorbed in the small intestine but rapidly fermented by bacteria in the large bowel(4). Typically in the UK, we consume moderate to high quantities of foods containing FODMAPs on a daily basis. It’s surprising how many ‘every day’ foods we consume that could be potential triggers for patients with IBS, due to their FODMAP content.

Prior to patients commencing on a low FODMAP diet, we firstly need to ensure suitability/appropriateness of the referral. Within NHS Lanarkshire, we firstly check to ensure the patient does not have Coeliac Disease or any symptoms which would act as a ‘red flag’ for further investigation to rule out any gastrointestinal disease. Once completed, patients receive an initial appointment for first-line dietary advice and one follow-up appointment within our general Out-Patient clinics. At this second appointment, if patients have not had adequate symptom relief and are appropriate, they are then transferred into our specialist low FODMAP IBS clinics. However, it is important to remember a low FODMAP diet isn’t appropriate for all patients with symptoms of IBS (e.g. constipation predominant IBS, or patients in whom psychological factors have a role in IBS pathophysiology).

In NHS Lanarkshire, patients going into the low FODMAP IBS clinic are seen twice. During the first appointment, I gather a detailed diet history from the patient to assess the FODMAP content of his/her diet, as this varies from individual to individual. Much of the consultation is spent going through suitable, alternative foods which patients can have, as-well-as educating patients on food labelling. The patient will be expected to maintain this diet strictly for 8 weeks before returning for their second appointment. Patients often look terrified when you outline the lists of foods which need to be excluded. One patient always sticks in my mind when she said “I’m not eating much now and from what you’ve said I think I’ll starve on this diet”. However, once we went through suitable alternatives, she was relieved and, ironically, when she returned 8 weeks later, she had actually gained weight, as the variety in her diet had significantly increased!

At the return appointment, if the patient has seen symptom improvement, he/she will enter into the food reintroduction phase of the low FODMAP diet. The shear thought of this reintroduction phase can be a daunting process. Patients can achieve such significant, symptom improvement while following the low FODMAP diet that they are often hesitant to reintroduce foods. Explaining to patients this is an exciting time for them to be able to find out their specific trigger foods is essential. Ultimately, we are educating patients to take ownership of the management of their condition.

An example of the dramatic, improvement patients can achieve, while following a low FODMAP diet is demonstrated in this brief case study.

A 29 year old female reported severe symptoms of: abdominal pain; bloating; flatulence; urgency to open-her-bowels; reflux and lethargy. At the time of her assessment, she was opening her bowels 12-15 times per day. She was regularly absent from work. She was terrified to use public transport and had stopped socialising with friends and family due to the embarrassment of her symptoms. She commenced the low FODMAP diet and returned 8 weeks later. In her own words, the low FODMAP diet had ‘worked wonders’ and changed her life. When we re-examined her symptoms, most of them had completely resolved and she classified those that remained as mild and affecting her only occasionally. The biggest change was in her bowel activity and she was now opening her bowels 2-3 times/day. She said her life was changing as she could now go out and socialise with friends and family. She also felt like a ‘normal’ adult again and one whose life didn’t revolve around ‘bathroom activity’.

Similarly, many other patients report dramatic improvements in symptoms. Here are a few comments I’ve gathered from patients;

‘At first I thought the diet would be a nightmare to follow but once I started to feel the benefits of it, it was no longer a chore. My wife even benefited from me completing the diet. I was no longer passing foul smelling wind or having to use the toilet constantly. What a difference it made to both of us’ Male aged 50.

‘My job involves travelling all over the world and this becomes problematic when you’ve got a crazy bowel without any control. Prior to going on the low FODMAP diet, I took Immodium all the time and avoided eating, if I had to go to a conference or travel. Now, I’m like a new woman, I no longer take Immodium and eat regularly throughout the day. Life is so much better and a little less stressful’ Female aged 32.

From this very brief article I hope you can see the effectiveness of this treatment and recognise the potential cost benefits that come from a reduction in prescriptions/medications, GP/consultant visits and unnecessary investigations. Not only does Dietetic-led FODMAP Clinics offer financial savings to the NHS but the clinical effectiveness of this dietary approach for IBS will potentially reduce sickness absence in those affected, and more importantly, it promotes and empowers patients to manage their condition with a successful outcome. Dietitians, within the NHS, now have the opportunity to use their expert knowledge to lead and promote the low FODMAP diet in managing patients with symptoms of IBS.


  1. Maxion-Bergemann S, Thielecke F, Abel F & Bergemann R. Costs of irritable bowel syndrome in the UK and US (2006) Pharmacoeconomics 24(1) pp21-37.
  2. Williams M: How CCGs can successfully and economically manage Gastro conditions in the new NHS (2013) Complete Nutrition Focus 5(3) pp51-53.
  3. Staudaher HM, Whelan K, Irving PM & Lomer MCE. Comparison of symptom response following a diet low in fermentable carbohydrates (FODMAPs) versus standard dietary advice in patients with irritable bowel syndrome (2011) Journal of human nutrition & dietetics 24 (5) pp487-495.
  4. Gibson PR & Shepard SJ. Evidence-based dietary management of functional gastrointestinal symptoms: The FODMAP approach (2010) Journal of Gastroenterology and Hepatology 25(2) pp252-258.

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