Exploring a patient-centred, diet-focused treatment paradigm for Inflammatory Bowel Disease

Abstract

Introduction: The relationship between diet and inflammatory bowel disease (IBD) is multi-dimensional and complex. Diet is implicated as an environmental factor in disease pathogenesis, however, the interaction between dietary factors and the induction and/or perpetuation of mucosal inflammation is poorly understood. Many people with IBD believe diet and disease are interrelated and subsequently modify their diets in the absence of defined diet therapy, however, this may not improve clinical, nutritional or quality of life (QoL) outcomes. Diet therapy for ulcerative colitis (UC) is under-researched though data proposes the pathogenesis of UC may be a sequelae of interactions occurring between dietary substrate, the gut microbiota and colonic epithelium. Aims: Therefore, the aims of this thesis were to: 1. Explore dietary beliefs and behaviours of people with IBD and to examine the inter-relationship between diet and QoL. 2. Examine the potential utility of diet therapy with defined mechanistic action in UC. Methods: A systematic scoping review was firstly undertaken to examine the dietary beliefs of people with IBD and to explore any associations with QoL. Additionally, a systematic review examining the adequacy of dietary fibre intakes and associated factors was performed. Following this, a cross-sectional study examining food-related quality of life (FRQoL) was undertaken to characterise FRQoL and identify any patient- or disease-related predictors of FRQoL in people with IBD. Thereafter, an open label pilot dietary-advice study was undertaken to investigate the tolerability of a novel pathogenically-designed diet (a sulphide-reducing diet) as therapy in people with mild-moderately active UC. The influence on disease activity, bacterial fermentation and patient-reported outcomes were examined. Lastly, in a case series of patients with refractory UC, diet therapy to augment and sustain the efficacy of faecal microbiota transplantation (FMT) was explored. Results: A complex dietary belief system informing dietary behaviours was identified in people with IBD and a high prevalence of food avoidance and restrictive dietary behaviours. Dietary fibre intakes were inadequate compared to control groups, irrespective of disease activity, and only 10-21% met national fibre recommendations. FRQoL in IBD patients was lowered by restrictive eating behaviours associated with fear, poor appetite and active disease. However, positive food-related outcomes were associated with surgery. An 8-week sulphide-reducing diet was well tolerated and adhered to, with clinical response occurring in 46%, endoscopic response in 36% and biomarkers of colonic fermentation were successfully modulated. Finally, sustained remission beyond 24-52 weeks was achieved using FMT and diet therapy, where diet may assist in engrafting donor ‘healthy’ microbiota. Conclusion: Diet is influential over many important aspects of living with IBD. Restrictive dietary behaviours are associated with poorer FRQoL. A sulphide-reducing diet signals therapeutic potential for UC and as an adjunctive therapy to FMT. Collectively, the studies within this thesis highlight important yet neglected areas of IBD care and identify areas where diet can provide added value, including as a possible therapy for UC. These findings warrant further examination as wide spread integration of diet into conventional treatment of IBD could dramatically change clinical practice, treatment outcomes and QoL for people with IBD.