Distinct microbial mediators link diet to inflammation in Crohns disease and ulcerative colitis

Background Inflammatory bowel disease (IBD) arises from complex interactions among diet, host and gut microbiome. Although diet influences intestinal inflammation, the microbial and metabolic pathways involved, and their differences between Crohn's disease (CD) and ulcerative colitis (UC), the two main subtypes of IBD remain unclear.

Objective To investigate how the gut microbiome mediates the effects of habitual diet on inflammatory activity in IBD. Design This longitudinal study included 198 adults (100 healthy controls, 49 CD, 49 UC), participants completed a validated food frequency questionnaire.

Dietary quality was evaluated using established indices (Alternative Mediterranean Diet, Healthy Eating Index-2015, Índice de Alimentación Saludable, Mean Adequacy Ratio, Plant-Based Dietary Indexes, Healthy Food Diversity). Participants also provided two stool samples (baseline and 6 months).

Shotgun metagenomics (n=366) enabled taxonomic and functional profiling. Causal mediation analyses were used to identify microbial features mediating the effect of diet on inflammation.

Results IBD patients exhibited lower dietary diversity, fibre intake and nutritional adequacy compared with controls.