Excessive consumption of melanin-rich foods in the daily diet can lead to the inability of pigmented substances to be absorbed and utilized by the gastrointestinal tract tissues, resulting in physiological black stool symptoms. Diseases of the upper gastrointestinal tract are a common cause of such adverse reactions, as organic lesions of local organs and tissues in the upper gastrointestinal tract can cause tissue ulcers and bleeding. The exuded blood enters the sigmoid colon, rectum and other intestinal tissues with the peristaltic action of the gastrointestinal tract, and is discharged from the anal tissues after the oxidation reaction with the fecal matter, thus causing black stools and sticky stools, but most of these patients also have complications such as abdominal distension and pain, nausea, vomiting and loss of appetite compared to the former.