Dietary Fiber Before Colorectal Cancer Surgery

This trial is testing whether taking a dietary fiber supplement before colorectal cancer surgery can help improve recovery and surgical outcomes. Fiber feeds healthy gut bacteria, and researchers believe improving the gut microbiome before surgery may reduce complications. Participants will take a fiber supplement in the weeks leading up to their planned bowel cancer operation. **You may be eligible if...** - You are 18 or older - You have been diagnosed with colorectal cancer and are scheduled for planned (non-emergency) surgery to remove the tumor **You may NOT be eligible if...** - You have previously had major abdominal surgery (other than appendix or gallbladder removal) - You have Crohn's disease, ulcerative colitis, or celiac disease - You currently have a stoma (bowel opening on the abdomen) - You are allergic to plants like lettuce, chamomile, artichokes, or related flowers (Asteraceae family) - You already eat more than 30g of fiber per day (women) or 40g per day (men) - You are currently using fiber supplements, probiotics, or prebiotics and are unwilling to stop - You are on a very strict diet (like gluten-free or ketogenic) and cannot change it - You have dementia or cannot fill out questionnaires in Dutch Talk to your doctor to see if this trial is right for you.