Black stool isn't always due to a big problem. There are many reasons stool could appear black, and iron supplements or even coffee could be to blame. This is especially true for people who have had ostomy surgery or a colectomy, because food is not being digested as fully as it is in people who have not had any abdominal surgery. However, if you have had gastrointestinal bleeding in the past, there is a foul smell, or the problem goes on for longer than a few days, that's a good enough reason to see your doctor.
Source
Causes
Black, Tarry Stools
Bleeding in the upper portion of your digestive system can cause black, tarry stools. Ulcers or another form of irritation in your esophagus or stomach known as gastritis can often cause bleeding. When the blood mixes with digestive fluids, it takes on the appearance of tar. Certain medications can also lead to black-colored stools. Iron supplements and bismuth-based medications, for example, can darken your stools. Sometimes, serious blood and circulation abnormalities in your digestive system can cause black, tarry stools. These can include the following:
- Bowel ischemia is a reduction of blood flow to the intestines.
- Vascular malformation is misshapen veins.
- Varices are large, protruding veins in the intestines.
Dietary Causes
The foods you eat can cause your stools to appear bloody, black or tarry. Eating red or black foods can give your feces a dark color without the existence of blood. The following can discolor your bowel movements:
- black licorice
- blueberries
- dark chocolate cookies
- beets
- red fruit punch
Symptoms
Black stools are a worrisome symptom because it may be due to a large amount of bleeding into the GI tract, most often from the upper GI tract including the esophagus, stomach, and duodenum. Red blood cells are broken down by digestive enzymes in the intestine and turn the stool black. These stools tend to be tarry (sticky), and very bad smelling. This can be a medical emergency and black tarry stools should not be ignored. Blood from nosebleeds or from dental procedures or mouth injuries can be swallowed and may be the cause of
black stool.
