Diets for inflammatory bowel disease: impact on microbiome and immunomodulatory microbial metabolites

Abstract

Diet plays a complex role in the management of inflammatory bowel disease (IBD), significantly influencing the microbiome and metabolome. Three key metabolites implicated in IBD are short chain fatty acids, bile acids and tryptophan, all of which can be modulated through diet. This study analyses the impact of various diets on these metabolites. Despite the anti-inflammatory effects of short chain fatty acids, their levels do not increase during successful remission with exclusive enteral nutrition. Additionally, changes in tryptophan and bile acids are non-specific across different diets, suggesting these metabolic shifts are secondary to dietary efficacy in IBD. Dietary therapies vary in efficacy across individuals, as the established microbiome may not produce the desired metabolites. This variability is further compounded by differences in immune responses influenced by genetic factors and disease duration. Furthermore, inflammation and symptom resolution do not always coincide, revealing a discrepancy in dietary impacts on IBD. These limitations highlight the need for a deeper understanding of the interconnectedness of disease heterogeneity, dietary effects, the microbiome, and their influence on the mucosal immune system to develop more personalised dietary therapies. While no single diet is universally effective for all IBD patients, future research should focus on establishing a more rigid definition of dietary interventions for IBD and their long-term effects on clinical outcomes.