Issue 130 irritable bowel syndrome and the low fodmap diet

CONDITIONS & DISORDERS

IRRITABLE BOWEL SYNDROME: THE LOW FODMAP DIET Rebecca Gasche Registered Dietitian, Countess of Chester Hospital NHS Trust

Rebecca has a keen interest and specialises in Gastroenterology Dietetics. She currently works in the Community setting in the Chester area, running clinics and group sessions to manage a wide range of gastroenterology conditions.

For full article references please email info@ networkhealth group.co.uk

Irritable bowel syndrome (IBS) is a long-term condition affecting the digestive tract, thought to affect one in five people in the UK.1 It is known that diet and lifestyle factors play a huge role in managing symptoms.2 This article looks at the low FODMAP diet in the management of IBS symptoms.

IBS can most commonly cause symptoms such as abdominal discomfort, an altered bowel habit and bloating, and can have a huge impact on a patient’s quality of life. Part of the difficulty in managing IBS is the wide variety and severity of symptoms that patients may experience and how these symptoms are often triggered by different things.

The low FODMAP diet was created in 2008 by a team at Monash University in Melbourne, Australia.

In 2009, researchers at St Guys and St Thomas’ hospital NHS Foundation Trust and King’s College London also began investigating this diet, eventually adapting it to suit the UK population.

In 2010, the low FODMAP diet first appeared in the UK British Dietetic Association’s IBS Guidelines.3 WHAT IS THE LOW FODMAP DIET?

FODMAP stands for: Fermentable Oligosaccharides Disaccharides Monosaccharaides and Polyols. A bit of a mouthful. These are short chain carbohydrates, or sugar alcohols that are components of, or added to, foods.

Normally, when we digest foods, they are broken down and digested in the stomach and small intestine. However, as these FODMAPs are poorly absorbed in the small intestine, they pass through to the large intestine, where they feed the bacteria and are fermented. This release of gas causes the symptoms of bloating and abdominal pain in patients with IBS. The process can also have an osmotic affect, which can lead to an altered bowel habit in IBS patients.

A number of studies, including randomised controlled trials; blinded, randomised rechallenge studies; observational studies and meta-analyses, have been thoroughly reviewed, demonstrating the efficacy of the low FODMAP diet and how it can improve patient symptoms.4,5 The low FODMAP diet has been seen to improve up to 86% of patients symptoms, having a clinically significant response and overall improvement in gastrointestinal symptoms.5 TYPES OF FODMAPS

Fructans: these include foods such as wheat, rye, onions, garlic and leeks.

Fructans are varying length chains of the sugar fructose.

Galacto-oligosaccharides (GOS): these include foods such as beans and pulses.

GOS are varying length chains of the sugar galactose.

Polyols: these are most commonly found in sugar-free mints and gums (containing sorbitol, xylitol and mannitol), avocado, sweet potato, cauliflower and broccoli. Polyols are sugar alcohols.

Fructose: these include foods such as honey, mango, sugar snaps and fruit juice/fruits in large portion sizes. Fructose is a single unit (monosaccharide) sugar.

Lactose: the most common sources of lactose is in milk and dairy products. It is a double unit (disaccharide) sugar.

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CONDITIONS & DISORDERS Figure 1: Updated guidelines on the management of IBS6

GUIDANCE

In 2016, Mackenzie et al completed a systematic review and updated the guidelines on the management of IBS.6 The new guidelines saw the removal of the ‘third line’ treatment of IBS which used elimination/empirical diets. Instead, the focus is now on first line treatment, being healthy eating, investigating food intolerances and probiotics (if the patient wishes to trial; the guidance also discusses informing the patient group on the limited evidence for probiotics and the potential placebo effect, however, that would warrant a whole new discussion!) and second line treatment of the low FODMAP diet (Figure 1).

The previous advice for third line management for IBS was based on limited evidence and with the emergence of the low FODMAP diet, strict elimination diets which are nonspecific are thought to be no longer relevant in its treatment.

DELIVERING THE LOW FODMAP DIET

When looking at how patients should be educated and guided through the dietary advice for IBS, the current guidance from the National Institute for Health and Clinical Excellence (NICE) state that dietary management for IBS should ‘only be given by a healthcare professional with expertise 42

in dietary management.’2 When looking at the low FODMAP diet more specifically, further studies have supported dietitians as the healthcare professional to deliver the dietary guidance, stating the reasons for this being that dietitians have an extensive knowledge of nutrition, health and disease and are the leading experts in educating patients on disease-specific dietary management.7 The fact that dietitians directly contribute to research elucidating the mechanistic basis and clinical efficacy of the low FODMAP diet, and that they are governed by an ethical code for evidence-based practice, provides more reasons to support them delivering the low FODMAP diet. One paper also concluded that dietitianled implementation of the low FODMAP diet is an effective strategy for the management of IBS, and that the trend for non-dietitian-led implementation of the diet is of concern, as there is no evidence on the clinical effectiveness or risks associated with such practices. For this reason, the importance of dietitian-led management in IBS needs increased recognition in clinical practice.7 Traditionally, the low FODMAP diet has been taught to patients in a one-to-one clinical setting

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It is currently not advised to follow the low FODMAP diet longer than eight weeks, partly due to its restrictive nature and partly due to the effects it can have on our gut microbiota.

and more recently in group education sessions.

A number of studies have been conducted to demonstrate the effectiveness of group sessions and the low FODMAP diet.7-10 The interest in delivering the low FODMAP diet in a group setting likely comes from the success of group education sessions for other conditions, such as diabetes, and evidence from a number of studies which demonstrate how group education has been shown to enhance patient acceptability of a treatment through a sharing of experiences with others with a similar condition.8,9 O’Keeffe and Lomer published a recent review which investigated the best delivery methods for the low FODMAP diet.7 They concluded that further research into group education is needed, as preliminary evidence suggests that it is a clinically effective and an economic model of service delivery. Overall, the review found that the group pathway was a more cost-effective model of service delivery, but demonstrated equal clinical effectiveness. It was also acceptable to patients.7 In addition to this, Joyce et al found group sessions to be an effective way of delivering the low FODMAP diet, also as effective as one-to-one sessions, and again highlighted the positives from group sessions, such as peer support and the discussion of similar experiences.10 Whigham et al concluded that group education is as clinically effective as

one-to-one education and highlighted that the cost of a QALY gain (quality-adjusted life year) for this group pathway is well below the £20,000 to £30,000 threshold for UK healthcare costs.11 LIMITATIONS/FURTHER RESEARCH

Despite the positive outcomes following the still relatively new revelation of the low FODMAP diet, it has of course generated concerns around the long-term effects of following the diet.

It is currently not advised to follow the low FODMAP diet longer than eight weeks, partly due to its restrictive nature and partly due to the effects it can have on our gut microbiota. There are a number of studies that have compared the low FODMAP diet with a habitual diet which demonstrate that the low FODMAP diet reduces the concentration of bifidobacteria.12,13 One study also indicated that the reductions in several bacteria (F prausnitzii, Actinobacteria and Bifidobacterium) noted during the restrictive phase of the low FODMAP diet, returned once the diet was supplemented with fructo-oligosaccharides, suggesting that these reductions are only temporary and should return during the reintroduction phase.13 It is also not clear on how following the low FODMAP diet long term can affect overall health of the colon. Some studies have suggested that the low FODMAP diet can cause a decrease in short chain fatty acids (SCFA).12 This is due

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CONDITIONS & DISORDERS to SCFAs being produced in the fermentation process of digesting foods, which is reduced whilst on the low FODMAP diet. However, other studies have contradicted these findings, stating no changes in SCFAs were noted whilst following a low FODMAP diet.14 The ‘reducing FODMAPs’ phase of the low FODMAP diet is restrictive and, at a glance, can appear very complex and overwhelming.

Patients may be put off by this and struggle to adhere to the diet. The nature of restrictive diets does not suit everyone, so, it is worth bearing in mind that despite good clinical outcomes for patients, others may lack interest, or perhaps even become too involved in thoughts surrounding food, risking disordered eating.15 Further to this, restricting low FODMAP foods may lead to nutrient deficiencies, as it has been seen that patients following a low FODMAP diet consume fewer carbohydrates.16 This is thought to be as a result of the diet’s exclusionary nature, rather than the low FODMAP diet itself.

Potential further research has been identified in studies suggesting that gut microbiota might be used to predict responders to the low FODMAP diet.17 This thought that evaluating individual baseline microbiome could lead to personalised low FODMAP dietary advice is exciting, but is an area that requires exploring further.

Contrary to the elimination phase of the low FODMAP diet, the reintroducing phase appears to have had less research, with only a few observational studies reported.18,19 This is, therefore, also a window of opportunity for

further research, to help us discover more about how the diet works.

Lastly, S Eswaran conducted a mini-review on the research on the low FODMAP diet so far, concluding that although the research into the diet appears promising, further research is needed in the following areas: the mechanisms by which FODMAP restriction improves symptoms; long-term effects/safety in terms of gut microbiota and potential nutritional deficiencies; standardisation of a reintroduction protocol; whether or not complete exclusion of all FODMAPs is necessary for full clinical benefit; and improving patient selection to enrich symptom response.20 CONCLUSION

Using the low FODMAP diet as secondary advice for management of IBS has proved successful so far, with good outcomes noted for patients.

However, with positives there comes limitations and further research into the areas of the effect on gut microbiota, long-term health effects and nutritional adequacy of the diet are required.

The low FODMAP diet may be adapted and personalised for a more individualised treatment, if further research into using gut microbiota as response predictors is undertaken.

The diet should be delivered by a qualified health professional and patients have responded equally to one-on-one advice and group education. Due to the effects known on the gut microbiota, it is also the responsibility of the healthcare professional to ensure that patients follow the diet within the correct timeframes.

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