Black stool is a somewhat unnerving symptom reflecting on the overall health of the human digestive system. Some people will experience this occurrence a single time while others will on a sporadic or chronic basis. At the very least, a black bowel movement could be indicative of something you ate recently.
Black stool is generally “tarry” in nature, producing a strong, foul odor not usually found in typical waste. When it is benign, black waste can be caused by the consumption of certain foods, supplements, minerals, or medications. This dietary connection is known as “false Melena” as medical Melena refers to blood from internal bleeding discoloring the stool.
Some foods, such as blueberries and black licorice, may cause false Melena. The more you eat of these dyed foods, the more likely you are to produce black bowel movements. Iron (either as a supplement or as contained in a multivitamin complex) is also known to tint waste. Some types of lead or bismuth-based medication create this effect as well.
If you produce black stool, particularly if it is recurring, and you have not recently consumed any of these items, it’s best to seek medical attention as soon as possible to rule out any internal bleeding or digestive illness. This way, you can address the problem quickly if a serious health issue is revealed as the underlying cause.
So while the origin of the black stool can be benign in nature, it is more likely indicative of a serious digestive condition, a major disease like cancer, or internal bleeding. In these cases, blood is the cause of the blackened waste.
When the black waste is caused by blood, the condition is referred to as true Melena, as previously mentioned. The reason the stool is black and not red (or tainted with noticeably bright red blood) is that the blood has been retained within the body for a while and has somewhat congealed. This blood likely stems from the upper, rather than the lower, portion of the digestive tract. According to Wikipedia, a gastrointestinal hemorrhage causes the stool to appear black because of “. . . oxidation of the iron in hemoglobin during its passage through the ileum and colon.”
Black stool differs from bloody stool even though both conditions stem from internal bleeding. Bloody stool (stool that is very red or has streaks of bright red blood in it) is called hematochezia and usually originates from the colon or rectum. Melena on the other hand, is generally caused by bleeding within the stomach or small intestine.
Various Causes of Black Stool
But what causes this upper digestive bleeding in the first place? The most common cause of Melena is a bleeding peptic ulcer, although other biological causes exist, such as gastritis, esophageal varices, or a Mallory-Weiss tear.
An ulcer, a sore of the stomach lining caused by a bacterial infection, can become aggravated and bleed. The overuse of certain NSAIDs (non-steroidal anti-inflammatory drugs) can also cause peptic ulcers, which can lead to bleeding again, and thus black stool.
Gastritis, or an inflammation of the stomach lining, can cause black waste to appear. Likewise, ruptured esophageal varices, the dilated veins in the lower esophagus’ wall, can create a black bowel movement. A much more rare condition called a Mallory-Weiss tear can also lead to blackened waste. This last malady occurs when the esophagus-to-stomach connective mucous membrane tears from violent coughing, intense vomiting, or other spasms and convulsions.
Melena can also occur in newborn babies a few days after delivery if they swallowed a bit of their mother’s blood while still inside the womb. This is not a cause for concern, however, and will clear up on its own as it naturally passed out the baby’s body.
Although Melena isn’t considered a medical emergency, proper medical attention and treatment is strongly advised. Call your doctor once you’ve discovered you are producing black stool, especially if you haven’t taken iron supplements or bismuth medication or recently eaten inordinate amounts of blueberries and black licorice.
Bear in mind that just because you notice a black bowel movement after consuming these products does not mean you have true Melena. Black stool caused by blood can be diagnosed only by a qualified physician, usually through a fecal occult blood test, which is collected by the patient at home and then examined by a medical lab. If Melena is properly diagnosed, other tests such as x-rays, a colonoscopy, a gastroscopy, or blood tests may confirm the underlying cause of the condition.