The efficacy of fermented foods as an adjunct therapy in ulcerative colitis - a literature review

Background: Ulcerative colitis (UC) is associated with dysbiosis of the gut microbiota, reduced short-chain fatty acid (SCFA) production, and a pro-inflammatory cytokine profile. Fermented foods contain prebiotic and probiotic elements which may correct these deficits but the strength of the human evidence supporting their use as a dietary adjunct in UC has not been consolidated.

Methods: A review was conducted of nine studies addressing fermented foods and UC or inflammatory bowel disease (IBD): two randomized controlled trials (RCTs) and one companion RCT specific to UC, three supportive studies in mixed IBD populations, two observational studies (one prospective cohort, one case-control), and two Cochrane systematic reviews of probiotics in UC used as an anchoring reference.

Results: In a 12-week placebo-controlled RCT (n=20), bifidobacterium fermented milk (BFM) significantly improved clinical activity index, endoscopic activity, and histological score versus placebo, alongside significant increases in faecal SCFA concentrations. A companion one-year maintenance RCT (n=21) using the same product found relapse in 3/11 BFM-supplemented patients versus 9/10 controls. A smaller trial (n=11) of a fermented vegetable beverage improved loose stool symptoms without significantly altering overall UC activity. Supporting studies in mixed IBD cohorts (n=20–305) showed probiotic yogurt consumption favourably shifted inflammatory cytokines, expanded regulatory T-cell populations, and increased beneficial gut bacteria. Population-level data corroborated these findings: a prospective cohort of 197,763 participants found yogurt intake associated with lower incident UC risk and a case-control study of 340 UC patients found yogurt (OR 0.52) inversely associated with UC while cheese showed no association. Cochrane reviews of probiotics for UC induction and maintenance of remission found the wider evidence base too heterogeneous and underpowered for firm conclusions.

Conclusion: Fermented foods, particularly fermented milk and yogurt, show a plausible benefit in UC including improved clinical and mucosal outcomes, favourable immune modulation, and lower population-level disease risk. However results are heterogenous and evidence remains limited to small trials from a narrow set of research groups. Larger multi-centre RCTs are needed before fermented foods can be recommended as an evidence-based adjunct therapy for UC.