Dietary Fiber Before Colorectal Cancer Surgery

The aim of this randomized controlled trial is to investigate the feasibility of increasing preoperative dietary fiber intake in individuals with colorectal cancer who will undergo surgery. This will be done using 1) digital personalized dietary advice or 2) a dried vegetable product compared to 3) habitual diet (control).

Rationale: Postoperative complications, affecting up to 50% of the patients with colorectal cancer (CRC) undergoing surgery, are associated with impaired quality of life and higher mortality rates. The investigators have previously shown an association between a higher preoperative dietary fiber intake and a lower risk of postoperative complications. Before large interventions aiming to evaluate potential causal relationships between dietary fiber and postoperative complications can be implemented, feasibility of increasing dietary fiber intake before CRC surgery needs to be explored.

Objective: To investigate the feasibility of increasing preoperative dietary fiber intake in CRC patients undergoing surgery via 1) personalized dietary advice (Vezel-UP tool), or 2) vegetable product containing natural fibers compared to 3) habitual diet (control group). Secondary objectives will be considered to generate preliminary (biological) data to support the design of a future large-scale intervention studies.

Study design: A randomized controlled trial with three groups: 1) Vezel-UP group, 2) vegetable product group, and 3) control group. The intervention period equals the time between diagnosis and surgery, which is on average \~4 weeks but will vary between individual patients depending on their characteristics (e.g., physical condition and tumor location) and waiting list.

Study population: 54 CRC patients who will undergo elective tumor resection.

Main study parameters/endpoints: The primary outcome is the change in dietary fiber intake, which is assessed via two 24hr dietary recalls at baseline and during and after the intervention. Secondary parameters are stool pattern, gastrointestinal symptoms, quality of life, fecal microbiota composition, fecal and plasma microbial metabolites levels (i.e., SCFA and indoles), and length of hospital stay.

Eligibility Criteria:
Inclusion Criteria:

* Age ≥18 years;
* Being diagnosed with CRC and planned to undergo elective CRC resection;

Exclusion Criteria:

* Previously have had a large abdominal resection, excluding appendectomy and cholecystectomy;
* Diagnosed with Crohn's disease, Ulcerative Colitis, Celiac Disease;
* Currently having a stoma;
* Known allergic reactions to plants from the Asteraceae (Compositae) family (e.g., lettuce, daisies, sunflowers, artichokes, sage, tarragon, chamomile, chicory etc.);
* Currently following a strict diet and unwilling or unable to change (e.g., gluten free or ketogenic diet);
* Currently using fiber supplements, prebiotics and/or probiotics and unwilling to stop using these for the duration of the intervention;
* Having a habitual dietary fiber intake \>30 g/day for women and \>40 g/day for men, measured with a food frequency questionnaire;
* Dementia or other cognitive disabilities that makes it impossible to fill out questionnaires correctly;
* Illiteracy (inability to read and understand Dutch).