The role of diet in Inflammatory Bowel Disease

Does diet cause IBD?

Maybe! Though answers to the questions of how and why remain elusive. In short, nobody would disagree that IBD is a condition associated with Westernisation and its alignment to industrial food manufacture and processed/ultra-processed foods. Increasing research has pointed towards particular foods being associated positively or negatively with subsequent risk of IBD, and interrogating the literature quickly throws up themes that support Western diet as important in IBD: fibre, fruits and vegetables, cereal and breastfeeding are good; sugar, meat and processed foods are bad. The gold standard for research in this field, however, is prospective follow-up of a healthy cohort, with prospectively collected dietary data and then comparison of persons who do and don’t develop IBD. Whilst such studies do exist, they are much rarer than retrospective case-control studies, which can make interpreting the literature quickly a difficult and perhaps misleading undertaking. Naturally, a more detailed review presents a more nuanced picture, and we will return to this shortly…

Can diet treat inflammation in IBD?

Yes! Indeed, for years exclusive enteral nutrition (EEN) has been first-line therapy for induction of remission in Crohn’s Disease in children. This practice is mainstream in paediatric gastroenterology for two reasons: 1) to avoid steroids and their associated side effects on growing children and 2) because it works! The benefits of diet in treating inflammation do not stop at puberty; the 2024 ECCO Guidelines on Therapeutics in Crohn’s Disease has a GRADE statement on EEN in adults in addition to a nutrition-focussed practice point (in preparation). 

EEN has traditionally not been a favoured induction therapy in adults due to concerns regarding tolerability and possible inferiority to high-dose corticosteroids. However, it is worth considering that steroids are problematic in adults, too, with associated mortality as well as morbidity [1]. Regarding efficacy, it is noteworthy that drug trials tend not to select corticosteroids as a control arm.

The science behind EEN is compelling, showing that the mechanism of action is underpinned by elimination of dietary antigens and changes to the microbiome and metabolome, with an associated impact on barrier function in addition to innate and adaptive immunity. Furthermore, EEN is associated with biochemical, endoscopic and radiological improvements [2]. 

Whilst EEN is an effective induction therapy, it is not a desirable maintenance option for most patients. However, it is also not where our dietary treatment options end. The groundbreaking trial of the Crohn’s Disease Exclusion Diet (CDED) not only met the primary endpoint of HBI<5 in 68% of patients, but also showed endoscopic improvement in those undergoing paired colonoscopies [3]. There has also been research into numerous other dietary interventions, including CD-TREAT, the Mediterranean diet, low-emulsifier diets and partial enteral nutrition (PEN), with studies of combination of advanced medical therapies with PEN underway [4]. 

To date, there is uncertainty regarding where dietary interventions fit into treatment algorithms for IBD, and how best to tailor diet to the individual patient. However, a 2019 survey distributed through the Dutch Crohn’s and UC patient association showed that our patients believe diet to be either equally or more important than medication in managing IBD [5]. With this in mind, a consensus paper on the role of diet and nutrition in IBD is long overdue.

Can diet help with IBD complications?

Patients with IBD commonly develop symptoms or complications that are not directly related to active inflammation. These may include irritable bowel syndrome (IBS)-like symptoms, intestinal obstruction, symptoms associated with post-surgical states, such as a stoma or ileal pouch-anal anastomosis, and short bowel syndrome.  Furthermore, there are special conditions that require considerations beyond the standard IBD mould, such as pregnancy and orofacial granulomatosis (OFG).  Another common question raised by patients and clinicians is, “Can diet help with IBD complications?”  

Our knowledge of the role of diet in specific IBD comorbidities and special conditions is variable, with most high-quality evidence relating to the more common conditions, such as IBS-like symptoms, for which a low FODMAP diet is used [6].  However, there is no supporting evidence for the use of diet in the treatment of some other common complications, such as risk of intestinal obstruction in the presence of small bowel strictures, and clinical practice is based entirely on knowledge of intestinal physiology, which has directed the convention of restricting bulking fibre.  Additionally, some conditions are rare, as in the example of OFG, and it is thus unlikely to be feasible to conduct large-scale trials assessing dietary interventions.

Again, targeted information from detailed review is required to guide practice in this area of uncertainty.

As a result of the complexity inherent in understanding diet and IBD, ECCO recently commissioned the first consensus on nutrition in IBD, with five working groups each undertaking a systematic review of the literature, applying Oxford levels of evidence and then developing evidence-based statements through two rounds of voting. The five topic areas are: Diet in aetiology and disease prevention; Nutritional assessment and optimisation; Diet as induction therapy for active disease; Diet as maintenance therapy for inactive disease; and Dietary management of comorbidities and special conditions. This work is underway and will be presented at ECCO in Berlin in February 2025 before publication in the Journal of Crohn’s and Colitis. Hopefully, you will then be better equipped to answer patients’ queries on this frequently raised and important topic!

References

1. Torres J, Bonovas S, Doherty G, Kucharzik T, Gisbert JP, Raine T, Adamina M, Armuzzi A, Bachmann O, Bager P, Biancone L, Bokemeyer B, Bossuyt P, Burisch J, Collins P, El-Hussuna A, Ellul P, Frei-Lanter C, Furfaro F, Gingert C, Gionchetti P, Gomollon F, González-Lorenzo M, Gordon H, Hlavaty T, Juillerat P, Katsanos K, Kopylov U, Krustins E, Lytras T, Maaser C, Magro F, Marshall JK, Myrelid P, Pellino G, Rosa I, Sabino J, Savarino E, Spinelli A, Stassen L, Uzzan M, Vavricka S, Verstockt B, Warusavitarne J, Zmora O, Fiorino G. ECCO Guidelines on Therapeutics in Crohn's Disease: Medical Treatment. J Crohns Colitis. 2020 Jan 1;14(1):4-22. doi: 10.1093/ecco-jcc/jjz180. PMID: 31711158.
2. Narula N, Dhillon A, Zhang D, Sherlock ME, Tondeur M, Zachos M. Enteral nutritional therapy for induction of remission in Crohn's disease. Cochrane Database Syst Rev. 2018 Apr 1;4(4):CD000542. doi: 10.1002/14651858.CD000542.pub3. PMID: 29607496; PMCID: PMC6494406.
3. Yanai H, Levine A, Hirsch A, Boneh RS, Kopylov U, Eran HB, Cohen NA, Ron Y, Goren I, Leibovitzh H, Wardi J, Zittan E, Ziv-Baran T, Abramas L, Fliss-Isakov N, Raykhel B, Gik TP, Dotan I, Maharshak N. The Crohn's disease exclusion diet for induction and maintenance of remission in adults with mild-to-moderate Crohn's disease (CDED-AD): an open-label, pilot, randomised trial. Lancet Gastroenterol Hepatol. 2022 Jan;7(1):49-59. doi: 10.1016/S2468-1253(21)00299-5. Epub 2021 Nov 2. PMID: 34739863.
4. Halmos EP, Godny L, Vanderstappen J, Sarbagili-Shabat C, Svolos V. Role of diet in prevention versus treatment of Crohn's disease and ulcerative colitis. Frontline Gastroenterol. 2024 Jan 9;15(3):247-257. doi: 10.1136/flgastro-2023-102417. PMID: 38665795; PMCID: PMC11042448.
5. de Vries JHM, Dijkhuizen M, Tap P, Witteman BJM. Patient's Dietary Beliefs and Behaviours in Inflammatory Bowel Disease. Dig Dis. 2019;37(2):131-139. doi: 10.1159/000494022. Epub 2018 Nov 2. PMID: 30391940; PMCID: PMC6381876.
6. Black CJ, Staudacher HM, Ford AC. Efficacy of a low FODMAP diet in irritable bowel syndrome: systematic review and network meta-analysis. Gut. 2022 Jun;71(6):1117-1126. doi: 10.1136/gutjnl-2021-325214. Epub 2021 Aug 10. PMID: 34376515.