Observational Investigation of the CDED in a Real World IBD Clinic

A prospective observational study, which will follow a cohort of adult CD patients who are prescribed the Crohn disease exclusion diet (CDED) during their routine clinical dietary therapy. The diet is composed of three phases, at the end of the first two phases we will evaluate whether the patient achieved remission and at the end of phase three the maintenance of remission. We intend to study achievement and remission rate in association to the diet adaptations made by dieticians at phase 1 and 2, together with patient's choice off food at the third phase under real world clinical setting and patient lifestyle characteristics.

This is a prospective observational study that will follow a cohort of CD patients who are prescribed the Crohn disease exclusion diet (CDED) during their routine clinical dietary therapy at the IBD clinic of the TLVMC. The CD exclusion diet (CDED), is a whole-food diet designed to reduce exposure to dietary components, hypothesized to negatively affect the microbiome (dysbiosis), intestinal barrier, and intestinal immunity. We intend to follow patients with proven clinically active disease from the previous 4 months. Disease activity will be determined by Harvey-Bradshaw index (4\<HBI\<16) and Calprotectin\>50g.

The diet is composed of three phases, the first two included 5 mandatory foods consumed daily to provide specific fibers and starches as substrates for short chain fatty acids-producing taxa from Firmicutes, as well as sources of lean protein that were low in animal fat to decrease Proteobacteria and improve intestinal permeability, while maintaining a balanced diet. The diet included avoidance or reduction of exposure to foods containing animal/dairy fat, high fat from other sources, wheat, red or processed meat and protein sources rich in taurine, emulsifiers, artificial sweeteners, carrageenans and sulfites. The second phase stepdown diet involves higher exposure to fruits, vegetables, and legumes along with some foods that are reintroduced with restrictions to increase food flexibility and relieve monotony. The third phase of the study, is considered a maintenance phase in which patients are advised to continue practicing the concepts of the previous two phases, but they may generally manage their diet freely.

In this observational study, we aim to describe our real-world experience with the CDED, in a tertiary referral center for IBD patients. We aim to characterize both the adaptations of the first two phases of the diet practiced by IBD dieticians, and the food choices made by patients during the third phase of the diet . We aim to associate both these determinants with clinical remission at the end of phase two and remission maintenance at the end of phase three respectively.

Data collection

Upon visits, patients will be asked to fill in food frequency questionnaire (FFQ), 3-days recall questionnaires, food related quality of life, CD symptom and pain questionnaire. Dieticians will be asked to meticulously describe the adaptations they have performed in the CDED and the reasons for them at baseline, week 6 and 12. The adaptation will be made in accordance to patient's symptoms and disease characteristics.

At each visit, patient will provide a fecal sample which will be used to test for calprotectin, a biochemical marker, specific for intestine inflammation. Together with Harvey-Bradshaw index (HBI) we will determine disease severity and activity levels. Fecal sample will also use to determine and monitor changes in microbiome composition.

Anthropometric and nutritional evaluation

Patient's weight (kg), height (m), waist circumference (cm) will be documented at each study visit, and body mass index (BMI) will be calculated. Handgrip strength will be measured by a handgrip dynamometer (JAMAR® hydraulic hand dynamometer), and body composition by body electrical impedance (INBODY diagnostic weight).

Eligibility Criteria:
Inclusion Criteria:

1. Age \>18 years
2. Clinically stable CD patients, constant medicinal regimen throughout the study period. Refractory to mesalamine at least 6 weeks, or steroids at least 2 week, or immunomodulator at least 12 weeks or biologics at least 12 weeks therapy, medical cannabis at least 2 weeks before the study.
3. Clinically active disease by CD symptoms score 4 \<Harvey-Bradshaw index (HBI) at baseline and Calprotectin\>50g/l / endoscopy / imaging proven active disease from the previous 4 months.

Exclusion Criteria:

1. Inability to sign informed consent and complete study protocol
2. Pregnancy