Gut Function After Colorectal Surgery: Exploring Feasibility using Food, Supplements, and Monitoring.

Preoperative Diet Participants receive structured guidance to optimise their preoperative diet. This includes: a written guide outlining high-fibre, antioxidant-rich, and fermented food options aimed at improving gut microbiota and butyrate production. A dietary checklist to support daily food choices. A food diary to monitor intake and encourage adherence. Optional access to a dietitian for questions or personalised support. Participants are responsible for preparing and consuming the recommended foods themselves. The dietary intervention is designed to be flexible and integrated into their usual meals, based on preferences and tolerability. Examples of what the diet might include: High-fibre foods: fruits, vegetables, legumes, whole grains Fermented foods: yoghurt, kefir, kimchi, sauerkraut Antioxidant-rich foods: berries, olive oil, leafy greens Nutrition drinks (where tolerated) Duration of the preoperative diet: Participants are encouraged to follow the dietary guidance for up to 2 weeks prior to surgery, or as soon as feasible after enrolment if surgery is scheduled sooner. Postoperative Supplementation Total duration: Caffeine supplementation and arginine supplementation both commence on postoperative day 1 (once cleared for oral intake). Caffeine tablet and plain gummies are continued for up to 5 days postoperatively or until hospital discharge. Arginine is continued for up to 14 days, depending on patient tolerance and discharge timing. Frequency of the intervention: Caffeine tablet 50–100 mg per dose once a day Plain gummies: three times daily Oral arginine: 9 g/day, administered in 2–3 divided doses per day Strategies to assess adherence: Participants complete a postoperative food and supplement diary. Capsule/sachet counts may be used to confirm supplement adherence. Research nurses also monitor compliance through inpatient review and follow-up. Group Allocation in a Non-Randomised Design This is a non-randomised, staggered cohort feasibility study. Participants are assigned to groups based on the timing of recruitment: Group 1 (control cohort): Participants enrolled during the first 3 months receive standard perioperative care and data collection only. Group 2 (intervention cohort): Participants enrolled after month 6 receive the same data collection plus the dietary and supplement interventions described above. Group allocation is therefore determined by study phase, not participant or clinician preference.