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

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A Mediterranean Diet Pattern may be beneficial as a support therapy for maintaining remission from ulcerative colitis.

Introduction

The management of ulcerative colitis (UC) may be influenced by diet through its effects on gut microbial composition and levels of inflammation. The aim of this randomised controlled trial (RCT) was to compare the efficacy of a Mediterranean Diet Pattern (MDP) with a Canadian Habitual Diet Pattern (CHD) (usual diet) for the management of UC disease activity.

Methods

This trial included 28 mild-moderate diseased UC patients in remission - inclusive of participants who were on a stable dose of UC therapy. Participants were randomised to either MDP (n=15) or CHD (n=13). MDP participants received one-on-one dietary coaching from a dietician whilst the CHD group continued with their regular diet. Health markers included nutrition and medical history, blood work, and stool analysis at baseline and week 12 with disease activity assessed using the Simple Clinical Colitis Activity Index (SCCAI) and Partial Mayo Scores for the two intervals. Biomarkers included:

• Complete Blood Count
• C-reactive protein
• Albumin
• Vitamin B12
• Vitamin D
• Short-chain Fatty Acids (SCFA)
• Faecal secretory Immunoglobulin A (SigA)
• Faecal DNA
• Faecal Calprotectin (FC)

Results

Difference in scores between baseline and week 12, per group:

• Clinically significant reduction in the primary outcome of SCCAI>1.5: MDP 4/15 (27%); CHD 3/13 (23%)
• Change in secondary outcome of FC: MDP no change (p=0.375); CHD increase in FC (p=0.0488)
• Change in SigA: MDP increase (p=0.0040); CHD unchanged (p=0.0803)
• Change in SCFA: MDP increase in total SCFA (p=0.0129); CHD decrease of Acetic acid (p=0.0398) and Valeric acid (p=0.0215) only
• Change in Bacteriome: Using the BIRDMAn tool the study showed notable changes in microbiome variation for both positively and negatively associated outcomes between the two groups (p=0.00018).

Conclusion

Despite the small size of this study (note: no sample size calculation was reported), a 12-week MDP intervention appears to decrease disease activity with improved SCCAI scores. Inflammatory markers (e.g. FC) in the MDP cohort remained unchanged but increased in 75% of the control group. The CHD group had lower levels of beneficial SCFA that has been shown to be associated with opportunistic infection related microbes.

• A standard Western Style diet (typically low in fibre with increased animal protein and ultra-processed food) is associated with both onset and progression of Inflammatory Bowel Disease (IBD).
• A Mediterranean diet that consists of legumes, whole grains, vegetables, fruit, nuts, seeds, olive oil, fish, poultry and dairy products is associated with reduced inflammation and improved gut microbiome diversity.
• A Mediterranean diet may be effective as an adjunct therapy for maintaining clinical remission of UC by lowering faecal calprotectin, increasing faecal SIgA, improving the diversity and abundance of the microbiome, decreasing the abundance of pathogenic microbes and increasing total SCFAs.
• However, given the established inflammatory nature of IBD it is advisable to introduce gut microbiome altering food options - in line with ongoing therapeutic intervention - slowly whilst constantly monitoring the patient.
• Note that the conclusions were based on a very small, select cohort with associations between specific nutrients (e.g. catechins found in grapes that metabolise quercetin to produce butyrate) based on previous studies inclusive of murine models.

• The background diet of two participants in the CHD cohort was similar to a Mediterranean type diet, which may have biased SCCAI scores and other biomarkers in this group due to the small sample size. Larger cohorts and longer trial periods are therefore needed to confirm tolerance, efficacy and safety of a MDP in IBD patients.
• The effect of a MDP on patients with more severe symptomatology still needs to be assessed.
• Future research should consider potential confounding factors and endoscopic (gold standard) analysis of mucosal healing.