For the estimated 10 million people worldwide living with ulcerative colitis or Crohn's disease, dietary choices represent one of the few modifiable levers patients can act on daily. Whether the Mediterranean diet — long celebrated for cardiovascular and metabolic benefits — meaningfully shifts the trajectory of inflammatory bowel disease has remained an open and clinically important question until now.
This PROSPERO-registered systematic review, drawing from PubMed, EMBASE, Scopus, and Web of Science through May 2025, synthesized evidence from 12 studies encompassing 1,615 adult IBD patients. The pool included three randomized controlled trials, one single-arm interventional trial, and eight observational studies spanning cohort, cross-sectional, and case-control designs. Across this heterogeneous body of evidence, higher adherence to the Mediterranean diet was associated with measurable improvements in clinical disease activity, systemic inflammatory markers, and patient-reported quality of life outcomes — effects plausibly mediated through favorable shifts in gut microbiota composition, increased short-chain fatty acid production, and reduced intestinal permeability.
This review arrives at a moment when the microbiome-diet-inflammation axis is among the most actively investigated frontiers in gastroenterology. Prior mechanistic work has established that Mediterranean diet staples — olive oil polyphenols, dietary fiber from legumes and vegetables, and omega-3-rich fish — selectively promote Lactobacillus and Bifidobacterium species while suppressing pro-inflammatory Proteobacteria. The key limitation here is structural: with only three true RCTs feeding into a largely observational evidence base, causal inference remains constrained. Adherence measurement also varied considerably across studies, complicating cross-study comparison. The exclusion of pediatric populations limits generalizability to a meaningful patient subgroup. Still, as an aggregated signal across 1,615 patients, the consistency of association is notable. This is best characterized as confirmatory and directionally strong evidence that warrants larger, longer-duration RCTs — rather than a standalone practice-changing finding.
