Crohn's disease (CD) is an inflammatory bowel disease in which there is an alteration of the homeostasis and functionality of the intestinal mucosa accompanied by a dysbiosis of the commensal microbiota. The analysis of different dietary strategies to achieve CD remission and reduce gastrointestinal symptoms concludes that it is nec-essary to restrict the intake of ultra-processed products and to promote the consump-tion of those with anti-inflammatory effects that improve intestinal permeability and dysbiosis. Based on previous studies conducted in other cohorts, mainly paediatric, we propose an experimental, prospective, randomised study in patients with active CD who do not show improvement with conventional pharmacological treatment. The control group will receive standard nutritional recommendations while the interven-tion group will be prescribed an exclusion diet supplemented with enteral nutrition. In the present project we plan to conduct a detailed study to determine the potential of the exclusion diet for the treatment and remission of CD in adult patients, with the hypothesis that this nutritional intervention will be able to modify and improve intes-tinal dysbiosis, inflammatory status and clinical and body composition markers in these patients.

An analysis of various dietary strategies to achieve remission of CD and reduce gastrointestinal symptoms concludes that it is necessary to restrict the intake of ultra-processed products while promoting foods with anti-inflammatory effects that improve intestinal permeability and dysbiosis. The European Society for Clinical Nutrition and Metabolism (ESPEN) acknowledges that there is insufficient evidence to recommend a specific diet and emphasizes the importance of individualization. Current scientific literature supports the use of the exclusion diet (ED) in CD, which is characterized by the exclusion of frozen or packaged foods due to their additive content and the inclusion of fresh, fiber-rich foods-owing to the benefits observed in symptom remission in the pediatric population. However, evidence in adults, although encouraging, remains limited. The ED is supplemented with a specific enteral nutrition formula that should not exceed 1250 Kcal/day and is administered at a proportion of 25-50%, depending on the phase of the diet. The first two phases last 6 weeks each (12 weeks in total) and include foods that must be consumed daily. In the final maintenance phase, starting from week 13, there are no mandatory foods, and a Mediterranean diet is promoted. The literature also advocates for modifying the dietary pattern by reducing ultra-processed foods and adhering to the Mediterranean diet after one year of initiating the ED.

On the other hand, evidence regarding the impact on body composition in patients with CD is scarce and heterogeneous, which justifies further research and the publication of higher-quality data. These findings could present an opportunity to improve the treatment of patients with CD and to incorporate body composition assessment into routine clinical practice.

The primary advantage of this dietary strategy lies in its balanced, sustainable, and palatable nature, making it easier to adhere to over time. This is largely due to its inclusion of dietary fiber and essential substrates necessary for the production of short-chain fatty acids. The exclusion diet is based on the elimination or inclusion of specific dietary components while ensuring a nutrient composition that supports growth and maintenance of lean body mass.

Foods and additives that should be excluded from this diet include those associ-ated with high fat intake (particularly from animal sources, such as red meat), dairy products, wheat, alcohol, yeast, and insoluble fiber. Additionally, food additives recommended for avoidance include emulsifiers, carrageenan, maltodextrins, sulfites, and titanium dioxide. Conversely, the diet should be low in taurine, rich in pro-teins and complex carbohydrates, and free of gluten or modified starches.

Inclusion Criteria:

• Subjects of both sexes over 18 years of age.
• A diagnosis of active luminal CD with small bowel involvement, with or without colonic involvement, prior to study inclusion.
• Active symptoms of CD at the time of initiation of the nutritional intervention.
• Active disease, defined as a Harvey-Bradshaw Index (HBI) > 4 and an objective measure of disease activity, such as an elevated inflammatory marker (CRP > 5 mg/L or 0.5 mg/dL, or calprotectin ≥ 250 µg/g) and/or a radiological imaging test (MR enterography or intestinal ultrasound) or an endoscopic test (ileocolonoscopy or capsule endoscopy).
• Ability and willingness to adhere to one of the nutritional interventions.
• Capacity to complete and sign the informed consent form.

Exclusion Criteria:

• Patients experiencing a severe flare that is associated with fistulizing tracts or strictures during the study period.
• Hospitalized patients.
• Patients with known intolerance or hypersensitivity to the components of the nu-tritional supplement Modulen IBD.
• Patients following another diet or who are participating in other nutritional trials.
• Patients scheduled for surgical intervention during the study period.
• Patients with active malignancy.
• Patients undergoing treatment with antibiotics or probiotics.
• Patients with other clinical conditions that may interfere with the implementation of the nutritional interventions (such as heart disease, celiac disease, uncontrolled diabetes, active infections, tuberculosis, or a positive stool test for Clostridium dif-ficile toxin).