Foods which causes black stool consist of Beets, Blueberries or blackberries in larger amounts, Licorice, uncooked red meat, or any food which contain considerable quantity of animal blood.
Bleeding: Black colored stool indicates blood passing through the stomach during digestion process. Hemoglobin iron is oxidized by stomach acid. Several stomach acids may appear in duodenum; the part of the small intestine between the stomach and the jejunum. Because of this phenomenon, if there is any bleeding arises from duodenum or above, will result in black, stinking stools that stick to the toilet. Causes of bleeding may include:
- Internal bleeding (Gastrointestinal, Rectal, Stomach, Nose, Mouth, Lung, or Spontaneous bleeding into the gut due to trobocytopenia, hemophilia, metastases, or sepsis)
- Stomach or duodenal inflammation (gastritis)
- Ulcer (Peptic, or due to alcohol, smoking, strong spices, or infection with H. pylori bacteria, Colon cancer)
- Stomach or duodenal cancer
- Esophageal varices due to liver cirrhosis (often in alcoholics), or portal hypertension
- Mallory-Weiss tear (a tear in the esophagus from violent vomiting)
- Nose or para-nasal sinuses (high blood pressure, tumor, injury)
- Mouth (tooth extraction, injury)
- Throat (severe inflammation, cancer)
Medications: Following medications, if taken by mouth, may cause black stools:
- Charcoal
- Iron supplements
- Pepto-Bismol (bismuth subsalicylate, an anti-diarrheal drug)
- Vanadium products, often used by bodybuilders
Poisons: Some poisons like Lead may result in black stools
Other reasons: Black stool may be due to clumps of bacteria, visible as pepper-sized specks, often found in small intestinal bacterial overgrowth (SIBO).
