Inclusion Criteria:  Age: 18-75 years old; Sex: Male or female Pathologically confirmed gastric adenocarcinoma or colorectal adenocarcinoma. Patients are ready to receive chemotherapy regimens containing platinum or irinotecan (targeted therapy could be used at the same time). Patients have not received any anti-cancer treatment before. patients are planned to receive the same chemotherapy regimen at least 2 cycles A baseline Eastern Cooperative Oncology Group (ECOG) performance status of 0-2. Adequate haematopoietic function of bone marrow: neutrophils≥1.5x109 / L, platelets≥75x109 / L; normal liver and kidney function: TBIL≤ 1 upper limit of normal (ULN); ALT and AST ≤2.5 ULN; creatinine≤1.5 ULN.  Exclusion Criteria:  (Patient-Generated Subjective Global Assessment, PG-SGA)>9 or severe malnutrition (weight loss > 10% or serum albumin < 30 g/L or body mass index < 18.5 kg/m2); Patients with severe heart, lung and brain diseases; chronic hepatitis infection, liver cirrhosis, chronic nephritis, kidney dysfunction, etc; Patients with infection-related fever; Patients who are known to be allergic or intolerant to any of the ingredients used in the study; Patients with long-term chronic diarrhea, abdominal pain, constipation or other digestive tract diseases; patients with gastrointestinal symptoms before chemotherapy (≥grade 2 NCI-CTCAE, version 4.0); Synchronously receive other treatments that may cause diarrhea, such as radiotherapy; Patients who take drugs for microecological regulation of digestive tract such as Combined Bifidobacterium, ChangTai oral liquid, etc; Patients take traditional Chinese medicine or antibiotics; Unable to understand and sign the informed consent form; participants in other clinical trials.