Healthy Volunteers Enteral Nutrition Study (HEN)

Crohn's disease is an immune mediated condition that can affect any area of the gastrointestinal tract. The etiology is still unclear but is thought to be an aberrant response to the gut microbiota, inducing intestinal and systemic inflammation. Given the role of the immune system in the pathogenesis of Crohn's disease, the cornerstone of therapy has been targeted immunosuppression. However, despite the advances in pharmacologic treatments that have been seen in the past 20 years, a significant number of patients either do not respond to therapy or lose response after experiencing a benefit. In addition, immunosuppression is associated with unwanted adverse effects. As such, there is a need to develop therapeutic approaches that address the underlying stimuli that leads to the inflammation of Crohn's disease. This is an outpatient randomized controlled trial of 20 healthy volunteers who will be assigned to either Partial Enteral Nutrition (PEN) defined as 60% of calories from Kate Farms Peptide 1.5 formula and 40% of calories from the Crohn's Disease Exclusion Diet (CDED) (N=10) vs. Exclusive Enteral Nutrition (EEN) defined as 100% of calories from Kate Farms Peptide 1.5 formula (N=10) for 3 days. The purpose of the study is to understand the changes in colon transit time and the microbiome and metabolome that result from consumption of the assigned diet. Blood and urine will be collected at screening and for 3 of 4 days that the participants are under study observation. Stool will be collected on all 4 days if the participant has a bowel movement on each day. Participants will also be given sitz markers on day one of the study and will undergo one or two x-rays. Diet surveys will also be collected during the 4 days of observation. Considering the link between gut microbiome and development of inflammatory bowel diseases, there has been a growing interest in dietary modifications aiming to treat or even prevent the development of disease. Dietary therapies are a potential therapeutic alternative in Crohn's disease. Exclusive enteral nutrition (EEN), the provision of 90% to 100% of daily caloric intake with a meal replacement formula, is as efficacious as corticosteroids in pediatric Crohn's disease and is promoted as a first-line treatment over corticosteroids. However, it is used less in adults as it is not well tolerated and leads to poor adherence. Partial enteral nutrition (PEN), the provision of approximately 50-80% of calories from a meal replacement formula, has emerged as a potential, better tolerated strategy to treat CD. Studies have shown that PEN may help to treat Crohn's disease even though it may not be as efficacious as EEN. The mechanisms by which enteral nutrition may be useful in the treatment of CD are unknown but some evidence points to immunomodulation of the gastrointestinal tract, promoting mucosal healing through changes in cytokine profiles, inducing microbiome changes and decreasing the exposure to food and additives that can reduce the epithelial barrier function. CDED is characterized by mandatory and optional foods. The mandatory foods are chicken breast, eggs, potatoes, apples and bananas. The optional foods are predominantly a range of fruits and vegetables and non-gluten containing grains. Because EEN and PEN with CDED appear to be comparably efficacious, it suggests that the food which is being excluded is more important than the quantity of formula consumed. This is further evidenced by the observation that the choice of enteral formula does not appear to impact the efficacy of EEN.6 The main barrier to use of EEN or CDED is the restrictive nature of the diet. The investigators hypothesize that better characterization of the biologic effects of EEN and PEN with CDED would allow for development of more liberalized diets that achieve comparable efficacy. The investigators propose to leverage modern omics technologies to characterize the microbiome and metabolome of EEN and PEN with CDED among healthy volunteers to aid in the development of rational and perhaps personalized diets for patients with Crohn's disease. The investigators have elected to conduct this research among healthy volunteers rather than in patients with Crohn's disease so as to avoid the confounding effect of intestinal inflammation.