Effects of Immunonutrition (Impact Oral®) in Patients Undergoing Surgery for Gastrointestinal Cancer

Inclusion Criteria: 1. Patients with upper or lower gastrointestinal cancer confirmed by histological method and scheduled for radical resection via open or laparoscopic surgery plus gastrointestinal reconstruction. Radiotherapy and/or Chemotherapy was not performed within 2 weeks before screening. 2. Age18-75 years old (include 18 and 75 years old). 3. Body Mass Index 18.5-28kg/m2 (include 18.5 and28kg/m2). 4. Life expectancy more than 3 months. 5. Plasma haemoglobin ≥ 90g/l. 6. Plasma albumin ≥2.5 g/dl. 7. No blood product infused within 1 week prior to screening. 8. Patients are informed for consent, and agreed to participate in the study and sign the informed consent. Exclusion Criteria: 1. Severe concomitant clinical conditions that could jeopardize the trial performance and follow-up. 2. Past history of gastrointestinal surgery or other treatment of digestive tract, and affect the nutrient absorption 3. Female patient who is pregnant or lactating woman. 4. Patient undergoing minor gastrointestinal cancer surgery such as confirmatory biopsy or endoscopy. Patient that has endoscopic tumour resection is also excluded. 5. Patient is not allowed any oral or enteral intake in the pre-operative phase of the study. 6. Having participated in another interventional clinical trial including those related to nutritional support within 4 weeks prior to the patient enrollment. 7. Other malignancies in the last 5 years (except for successfully treated in situ basocellular skin and in situ cervical uterine tumours). 8. Patient who is not willing and not able to comply with scheduled visits and the requirements of the study protocol. 9. Planned chemotherapy, radiotherapy or immunotherapy during the first 7 days following the surgical tumour resection. 10. Patient with liver and kidney dysfunction (alanine aminotransferase ALT ≥ 2 times the upper limit of normal; total bilirubin TBIL ≥ 2 times the upper limit of normal; creatinine Cr ≥ 2 times the upper limit of normal). 11. Known to have diabetes or fasting blood glucose≥ 10mmol/L. 12. Known to have hyperthreosis or hypothyreosis 13. Patient currently treated with Omega-3 fatty acid-containing fat emulsion, glutamine, thymosin, hormone, thyroxine, growth hormone, anti-TNF biological. 14. Known to have allergic history to any component of the investigational product. 15. Uncontrolled psychological disease.