Functional Profiling Demonstrates That a Sulfide-Reducing Diet Achieves Microenvironmental Targets in Ulcerative Colitis

BACKGROUND: As a dietary approach to reducing inflammation in ulcerative colitis, the 4-SURE (4 Strategies to Sulfide Reduction) diet was designed to correct pathogenic alterations of excessive protein fermentation and hydrogen sulfide (H2S) production in the distal colon. We aimed to perform a deep functional analysis (microbial and metabolomic) of the feces of 28 adults with mild-moderately active ulcerative colitis who adhered to the 4-SURE diet over 8 weeks to explore whether the 4-SURE diet could modulate the intraluminal environment as intended.

METHODS: Fecal samples were collected at week 0 and 8 of dietary intervention, processed and aliquoted. Metagenomic sequencing was undertaken to identify changes in H2S-metabolizing genes, while gas chromatography-mass spectrometry was used to analyze fecal volatile organic compounds and H2S production.

RESULTS: The 4-SURE diet significantly increased alpha diversity between weeks 0 and 8. By random forest plot classifier, the abundance of taxonomic groups comprising known H2S-producing genera were markedly lower at week 8, specifically Odoribacter and Peptostreptococcaceae, and were of highest importance in discriminating between before- and after-diet samples. The capacity for bacterial H2S metabolism was altered with diet, with differences in 12 of 67 analyzed sulfur-metabolizing genes identified. H2S production and indole, a specific marker of protein fermentation, were significantly decreased due to the diet.

CONCLUSIONS: Here, we demonstrate that the objectives of the 4-SURE diet were fulfilled. This application of deep functional analysis to a dietary intervention study is novel and highlights an exemplar framework for including microbial and metabolomic biomarkers of pathogenic relevance in the analysis of therapeutic diet strategies. (Australian New Zealand Clinical Trials Registry, Number: ACTRN12619000063112).