The goal of this clinical study is to learn whether oral histidine supplementation may be safely used to support antitumor immune function during standard colorectal cancer treatment.

Participants with colorectal cancer in the supplementation group will:

Take 2g oral histidine once daily during standard colorectal cancer treatment; Provide blood samples before and after supplementation; Attend regular follow-up visits for laboratory tests, safety assessment, and treatment evaluation.

Inclusion Criteria:

1. Patients aged 18-80 years, regardless of sex.
2. Body mass index (BMI) ≥18.5.
3. NRS-2002 score <3.
4. Diagnosed with stage II or higher colorectal cancer who require pharmacological intervention.
5. Capable of oral intake of medication.
6. Willing to participate in the study and provide written informed consent.

Exclusion Criteria:

1. Participation in other interventional clinical trials (including drugs, nutritional supplements, medical devices, etc.) within 4 weeks prior to enrollment.
2. Presence of ascites, severe diarrhea, intractable vomiting, severe malabsorption syndrome, paralysis, mechanical intestinal obstruction, or active gastrointestinal bleeding.
3. Allergy to sample components.
4. Current use of other nutritional supplements that may affect the validity and effectiveness of the study results.
5. Pregnant, lactating female patients or women with fertility who test positive in the baseline pregnancy test.
6. Presence of cognitive impairments or mental illnesses that prevent understanding of the study procedures.
7. Presence of any other conditions, judged by the researcher, make the participant unsuitable for participation in the study.