Issue 135 fibre and inflammatory bowl disease

COVER STORY

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.

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FIBRE AND INFLAMMATORY BOWEL DISEASE In this article, the latest evidence for dietary advice and inflammatory bowel disease (IBD) will be reviewed, with particular focus on dietary fibre.

IBD includes the diseases ulcerative colitis (UC) and Crohn’s disease, which are long-term conditions that cause inflammation of the gut. Crohn’s disease can result in inflammation anywhere in the digestive tract, from the mouth to the anus; however, it is most commonly seen in the small intestine or colon.

Inflammation caused by UC is seen only in the colon and rectum and usually only the inner lining of the bowel is inflamed.1 It is unclear what causes IBD, but it is thought to be a combination of genetics and individual immune systems.

Smoking is linked with an increased risk of developing Crohn’s disease.2 IBD can cause unpleasant symptoms, such as abdominal pain, loose and frequent bowel movements, fatigue and weight loss as a result of malabsorption.

CURRENT DIETARY ADVICE

NICE guidance states that patients with Crohn’s disease should be offered advice on diet and nutrition, however, in the guidelines for UC, advice on diet is only mentioned when a patient is considering surgery.3,4 This only very brief advice in the guidance is likely due to the lack of robust evidence when it comes to diet and IBD, meaning that clinicians need to delve a little into the research to provide nutritional support to IBD patients.

Currently, there are no proven dietary recommendations for IBD, as dietary intervention trials have been

limited by their lack of a placebo control group and the difficulty in capturing dietary intake with the potential for complex interactions between foods.

Furthermore, dietary trials may not detect significant differences for patients on specific drug therapies.5 Despite a lack of robust evidence for diet and IBD, there are a number of diets which patients have been known to turn to in order to improve the symptoms caused by IBD. These include: the specific carbohydrate diet (SCD); the low fermentable oligosaccharide, disaccharide, monosaccharide and polyol (FODMAP) diet; the Paleolithic diet (Paleo) and the anti-inflammatory diet (IBD-AID).5 These diets have been mentioned in literature, but only through anecdotal evidence, and are, therefore, not in the official guidelines for managing IBD. Saying this, if these are the diets that patients are trialling to manage their diseases, it is important that healthcare professionals are aware of them and can advise accordingly.

Despite the lack of evidence for diets to manage IBD, there is some evidence to support specific diets in certain situations, for example, enteral nutrition may be used during a flare up of Crohn’s disease, or a low residue (low fibre) diet may be used if there are strictures (narrowing of the bowel). The www.NHDmag.com June 2018 - Issue 135

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CONDITIONS & DISORDERS

Therapeutically, a low-fibre diet is part of the treatment in acute relapses of IBD (as well as other conditions such as irritable bowel syndrome and diverticulitis). . . . upon achieving remission, the amount of fibre should be systematically increased until achieving the recommended amount of fibre in a healthy diet. use of enteral nutrition for the management of Crohn’s disease was first described in the 1970s.6 Exclusive enteral nutrition has been seen to improve the symptoms of Crohn’s disease as it gives the bowel ‘rest’ and allows for mucosal healing, as well as being shown to reduce the production of bacterial metabolites within two weeks and reducing the bacterial coating with immunoglobulin.7 Enteral nutrition is usually taken for six to eight weeks and can use elemental or polymeric oral nutritional supplements, or feeds. If patients experience stricturing Crohn’s, the ESPEN guidelines recommend that a diet with modified texture or enteral nutrition may be advised.8 The guidelines go on to say that in patients with radiologically identified but asymptomatic stenosis of the intestine, it is common to recommend a diet which is low in fibre, but there is no robust data to support this apparently logical approach. When symptoms are present, it may be necessary to adapt the diet to one of soft consistency, perhaps predominantly of nutritious fluids.8 A literature review by Rhodes and Richman9 reported that indirect evidence for diet and IBD suggests that Crohn’s patients should have a diet that is low in animal fat, avoids foods that are high in insoluble fibre and avoids processed fatty foods. Supplementary vitamin D should be considered and dairy products, if tolerated, 12

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can be consumed to help ensure adequate calcium intakes. For UC, there were again fewer recommendations, stating that patient’s diets should be low in meat - particularly red meat and processed meats - and margarine should be avoided. There is weak evidence that olive oil might be protective and that strict avoidance of dairy products and/or lactose is not justified on the basis of current evidence. However, this advice keeps in line with other research on diet and IBD, stating that there is little robust evidence for these recommendations, indicating that further research into this field is needed. The published guidance provided by professional bodies varies considerably between different sources and is often based on consensus of opinion rather than evidence.

DIETARY FIBRE

I wanted to focus this article on dietary fibre, as from my own clinical experience it is something that is often talked about with IBD patients, but understand that actual evidence for dietary recommendations and fibre in IBD is poor.

Firstly, what is dietary fibre?

Dietary fibre can be described as a component of food that ‘includes all carbohydrates that are neither digested nor absorbed in the small intestine and have a degree of polymerisation of three or more monomeric units, plus lignin’.10 If

that’s a little too wordy for you, it is also often described as the ‘roughage’ in our diet. It helps to regulate our bowel movements and diets high in fibre have been linked to reducing the risk of diabetes and bowel cancer, as well as helping to lower cholesterol. Historically, it has been broken down into insoluble fibre and soluble fibre. Insoluble fibre is more of the definition of that roughage; it isn’t digested and adds bulk to our stools. It can be found in wholegrains and the skins/seeds/piths of fruits and vegetables.

Soluble fibre helps draw water into our stools, as well as binding to substances such as cholesterol and glucose, slowing their absorption. It is largely found in oats, beans, pulses and the inner flesh of fruits and vegetables. The terms ‘insoluble’ and ‘soluble’ have, however, been discouraged from being used in the clinical setting, with the argument that all fibrous foods contain a mixture of both.

Recent research undertaken by Wedlake et al concluded that excluding gastrointestinal obstruction, there was no evidence that fibre intake should be restricted in patients with IBD, and that some studies suggest that dietary fibre in UC may be beneficial, stating that a reduced relapsed rate was seen in diets with fibre, compared to a no fibre diet. The general consensus of this review is that fibre should be encouraged in IBD, unless there is stricturing. It also discussed the potential anti-inflammatory role of fibre and that this merits further investigation.11 A review on the literature conducted in 2013 by the British Dietetic Association (BDA) gastroenterology specialist group, also largely discussed dietary fibre only in relation to

stricturing Crohn’s disease. They concluded that there are no clinical trials to support the use of decreasing dietary fibre to reduce the risk of bowel obstruction or to reduce gastrointestinal symptoms in stricturing Crohn’s disease, and that dietary fibre is contraindicated. This is due to the fact that, again, there is no data to give evidence-based recommendations. Despite the lack of evidence to support it, the review paper goes on to say that avoidance of coarse and poorly fermented fibre is mandatory in the presence of strictures and that fermentable fibre may contribute to the production of large quantities of gas close to a stricture, which in turn could induce uncomfortable symptoms and that a low-fibre diet would be less likely to produce obstructive symptoms in patients with inflammatory strictures and reduce the risk of bowel obstructions. This evidence has limited clinical impact because it is only expert opinion. There are no national guidelines that have examined the evidence for this practice.

Furthermore, they concluded that the distinction between a low-fibre and a low-residue diet is unclear and there are no universally agreed definitions. Consequently, there is wide variation in clinical practice.12 The review concludes with practical recommendations of dietary advice for stricturing Crohn’s disease, which excludes any foods that may cause a mechanical obstruction or prestenotic pain as a result of excessive gas production (e.g. fibrous parts of fruits and vegetables, wholegrains, nuts and seeds, gristle on meat, skin on meat or fish, edible fish bones). It also writes that patients following dietary advice for stricturing Crohn’s disease should be assessed and reviewed by a

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CONDITIONS & DISORDERS

If there’s one thing I’ve learnt from writing this article, it is that there is a definite lack of evidence when it comes to diet, but in particular fibre and IBD! dietitian to ensure that the diet is nutritionally complete. The degree of dietary modification will depend on the nature and extent of the stricture and should be reviewed in line with the medical and/or surgical management in discussion with the IBD team.12 An additional study published by the BDA agrees that strictures lead to localised, persistent narrowing and can be inflammatory or fibrotic and, based on expert opinion, only dietary fibre is contraindicated.13 There have been a number of further studies which demonstrate that a diet high in fibre is beneficial to both patients with UC and Crohn’s disease and may decrease the incidence of the disease.14,15 Interestingly, despite the number of studies that recommended a healthy, high fibre diet in IBD (without strictures), it is known in clinical practice to advise patients to follow a short-term low residue diet if they are experiencing the symptoms of loose, frequent and urgent bowel movements, usually during an acute flare up of the disease state. In case of a flare-up, a low residue diet can reduce the frequency and volume of stools and induce a primary remission in disease. Therapeutically, a low fibre diet is part of the treatment in acute relapses of IBD (as well as

other conditions such as irritable bowel syndrome and diverticulitis). As previous evidence suggests, upon achieving remission, the amount of fibre should be systematically increased until achieving the recommended amount of fibre in a healthy diet.16 I do feel that this needs to be tailored to individuals, as from my own clinical experience, I understand that some patients struggle to tolerate a high fibre diet.

CONCLUSION

If there’s one thing I’ve learnt from writing this article, it is that there is a definite lack of evidence when it comes to diet, but in particular fibre and IBD! Most literature reviews concluded that further research is required. The most robust evidence suggests that reducing fibre is only suitable in stricturing Crohn’s disease; however, we know therapeutically that it is also beneficial during an acute flare up of IBD and may relieve symptoms during this time.

When looking at general dietary advice for IBD, the use of additional diets such as the specific carbohydrate diet and low FODMAP diet may be used. Nevertheless, the current evidence base is not strong enough to be advising these at present.

NETWORK HEALTH DIGEST

A wealth of useful dietetic resources for all dietitians and nutritionists

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Date of preparation: May 2018 ANUKANI180098a

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