A Mediterranean Diet Pattern Improves Intestinal Inflammation Concomitant with Reshaping of the Bacteriome in Ulcerative Colitis: A Randomised Controlled Trial

Abstract Background and Aims Dietary patterns are important in managing ulcerative colitis [UC], given their influence on gut microbiome-host symbiosis and inflammation. We investigated whether the Mediterranean Diet Pattern [MDP] vs the Canadian Habitual Diet Pattern [CHD] would affect disease activity, inflammation, and the gut microbiome in patients with quiescent UC. Methods We performed a prospective, randomised, controlled trial in adults [65% female; median age 47 years] with quiescent UC in an outpatient setting from 2017 to 2021. Participants were randomised to an MDP [n = 15] or CHD [n = 13] for 12 weeks. Disease activity [Simple Clinical Colitis Activity Index] and faecal calprotectin [FC] were measured at baseline and week 12. Stool samples were analysed by 16S rRNA gene amplicon sequencing. Results The diet was well tolerated by the MDP group. At week 12, 75% [9/12] of participants in the CHD had an FC >100 μg/g, vs 20% [3/15] of participants in the MDP group. The MDP group had higher levels of total faecal short chain fatty acids [SCFAs] [p = 0.01], acetic acid [p = 0.03], and butyric acid [p = 0.03] compared with the CHD. Furthermore, the MDP induced alterations in microbial species associated with a protective role in colitis [Alistipes finegoldii and Flavonifractor plautii], as well as the production of SCFAs [Ruminococcus bromii]. Conclusions An MDP induces gut microbiome alterations associated with the maintenance of clinical remission and reduced FC in patients with quiescent UC. The data support that the MDP is a sustainable diet pattern that could be recommended as a maintenance diet and adjunctive therapy for UC patients in clinical remission. ClinicalTrials.gov no: NCT0305371