After surgery for gastrointestinal cancer (stomach cancer, pancreaticobiliary cancer, colorectal cancer), many patients experiences various symptoms such as weight loss, diarrhea, constipation and excessive gas due to structural and functional changes in the gastrointestinal tract. These changes are thought to be influenced by alterations in gut microbiota following surgery, but prospective studies are still lacking. It is anticipated that the prebiotic effects of red ginseng may lead to positive changes in total gut bactera after gastrointestinal caner surgery.

Through this study, Investigators aim to investigate the impact of red ginseng consumption on gut microbiota composition, gastrointestinal symptoms, and nutritional status improvement following surgery for gastrointestinal cancer.

Inclusion Criteria:

1. Pathologically diagnosed with gastrointestinal cancers (stomach cancer, pancreatobiliary cancer, colorectal cancer) prior to surgery.
2. Clinically staged and anticipated to not receive adjuvant chemotherapy after surgery.
3. Eligible for complete surgical resection (R0 resection).
4. ASA (American Society of Anesthesiologists) score of 3 or below.
5. Intereseted in health functional foods.
6. Not consumed probiotics or prebiotics for at least three months prior to study enrollment.
7. Willing to refrain from consuming additional probiotics or prebiotics during the study period, apart from the provided red ginseng tablets.

Exclusion Criteria:

1. Patients aged 80 years or older.
2. Patients who received neoadjuvant therapy before surgery.
3. Patients with underlying gastrointestinal disorders (e.g., inflammatory bowel disease, ulcerative colitis, Crohn's disease, galactose intolerance, lactase deficiency, glucose-galactose malabsorption, short bowel syndrome, other hereditary gastrointestinal diseases, and autoimmune diseases).
4. Patients unable to orally consume red ginseng tablets.
5. Patients with a history of previous abdominal organ surgery, radiation therapy, or chemotherapy.
6. Patients with intestinal obstruction before surgery.
7. Patients regularly taking probiotic or prebiotic supplements.
8. Patients requiring formation of an ileostomy after surgery.
9. Patients with uncontrolled diabetes that may affect gastrointestinal function.
10. Patients with underlying conditions such as liver failure or renal failure.
11. Patients allergic to red ginseng.
12. Patients who received more than two weeks of antibiotic treatment during hospitalization.

The participating physicians in the study are kept unaware of which group each patient belongs to. However, patients are randomly divided into the Red ginseng and Control groups by research nurses, and they become aware of their group assignment (whether they will take red ginseng tablets or not) in a single-blind study format.