What causes black stool?
Oct 14, 2022
Source: Cainiu Health
Dr. Zhao Haiming
Introduction
Consuming large amounts of foods containing melanin can easily result in black stool. Patients who have recently taken iron supplements or gastric mucosal protective agents are also prone to develop black stool. Individuals with ulcerative lesions in the digestive system, leading to long-term chronic bleeding of organ mucosa, or those with hepatobiliary diseases such as gallstones or liver hemangiomas that cause blood vessel rupture and blood leakage into the feces, may also commonly experience black stool.
Black stool may be caused by dietary factors, medications, underlying medical conditions, and other reasons.
1. Dietary factors
Consuming large amounts of foods containing dark pigments—such as chocolate, pork blood, or duck blood—can easily discolor the stool, resulting in black stool. This is a normal physiological phenomenon, and stool color typically returns to normal gradually after discontinuing these foods.
2. Medication factors
Taking iron supplements such as ferrous sulfate or ferrous succinate may increase iron levels in the stool, and oxidized iron can lead to black-colored stool. Additionally, patients who regularly take gastric mucosal protectants like bismuth aluminate or rhamnus bismuth magnesium may also develop black stool due to oxidation of bismuth.
3. Medical conditions
Peptic ulcer diseases such as gastric ulcers or duodenal ulcers can cause chronic, slow bleeding from the mucosa of the digestive organs. Liver and bile duct disorders such as gallstones or liver hemangiomas may lead to vessel rupture, allowing blood to leak into the stool. Both scenarios can result in black stool.
