Background: Crohn's disease (CD) is characterized by intestinal inflammation. Diet is a risk factor for inflammatory bowel diseases such as CD and represents a promising adjunctive treatment, yet there are few well-controlled dietary intervention studies in CD patients. Fiber may have beneficial effects; however, most CD patients are told to avoid high-fiber foods. We conducted a longitudinal patient-preference study to examine the effect of a catered low-fat, high-fiber diet (the Mi-IBD diet) on CD symptoms, inflammation, and the microbiome. Methods: CD patients (n=73) received one-time diet counseling (Group 1, n=23), the Mi-IBD diet (Group 2, n=26), or the Mi-IBD diet along with a healthy household control (Group 3, n=24 patient-HHC dyads). The Mi-IBD diet was catered for 8 weeks, and CD symptoms were recorded. Serum samples were collected to measure inflammatory marker levels and evaluate systemic changes via proteomic analyses (SomaScan Discovery v4.1 assays). Stool samples were collected to perform metabolomic analyses. Results: At baseline, CD patients had a low-fiber, high-fat diet. One-time diet counseling did not result in dietary changes. In contrast, catering led to marked dietary changes in CD patients (increased fiber intake, decreased fat intake; all ps < 0.001) and high adherence rates (96%). Group 3 exhibited improvements in CD symptoms (PRO2 and sCDAI scores). Proteomic analysis revealed higher baseline serum levels of proinflammatory proteins (SAA and CRP) in CD patients than in HHCs; these levels decreased with the catered diet. The diet also improved fecal metabolites related to protein and energy metabolism as well as markers of oxidative stress and inflammation in CD patients. Conclusion: A nonpharmacological approach involving a high-fiber, low-fat diet to manage CD was well tolerated, even by patients with fibrostenotic CD. These findings fill a gap in development of dietary recommendations for CD patients.

MTA has received research funding from The Leona M. and Harry B. Helmsley Charitable Trust and the Crohn's and Colitis Foundation. She has served as a consultant for or is on the advisory board of the following companies: AbbVie Inc., Amgen, Bristol Myers Squibb, Celsius Therapeutics, Eli Lilly and Company, Gilead Sciences, Janssen Pharmaceuticals, Matera Prima, and Pfizer Pharmaceutical. MTA has served as a teacher, lecturer, or speaker for the following companies: Janssen Pharmaceuticals and Takeda Pharmaceuticals. All other authors declare that they have no conflicts of interest.

NCT04213729

This research was supported by a grant from The Leona M. and Harry B. Helmsley Charitable Trust to MTA.

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

The IRB of the University of Miami gave ethical approval for this work (protocol number 20190548).

I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.

Yes

I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

Yes

I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.

Yes

Individual participant data will not be shared to preserve patient privacy.