Observing a sudden change in stool color, especially a shift toward a dark or black hue, often creates alarm. Can eating cherries cause your poop to turn black? Yes, consuming a generous amount of this fruit can lead to a noticeable, though harmless, darkening of the stool. This temporary color change results from naturally occurring compounds within the fruit that interact with the digestive process. Understanding this benign dietary effect is important when contrasting it with changes that may signal a medical concern.
The Pigment Behind the Color Change
The darkening effect of cherries is due to their high concentration of anthocyanins. These water-soluble pigments are responsible for the vibrant dark red, purple, and bluish-black colors found in many fruits and vegetables. Cherries, particularly the darker varieties, contain significant levels of these pigments.
When cherries are consumed, these anthocyanins travel through the digestive tract. The body is less efficient at fully processing and absorbing these dark pigments. As a result, a substantial portion of the unabsorbed anthocyanins passes through the intestines along with the waste material.
During this journey, the pigments can undergo slight chemical changes due to digestive enzymes and the acidic environment of the digestive tract. This interaction causes the compounds to appear even darker by the time they are excreted. Consequently, the stool can take on a color ranging from deep maroon or dark green to a near-black appearance. This change is transient, resolving within one or two days after the cherries have been fully processed.
Differentiating Dietary Darkening from Medical Concern
When stool appears dark or black, it is necessary to distinguish between a benign dietary cause and a potentially serious medical condition. The discoloration caused by cherries or other foods is known medically as pseudomelena, which is harmless. In contrast, melena is the medical term for black, tarry, and sticky stool that results from bleeding in the upper gastrointestinal tract, such as the stomach or duodenum.
The appearance of true melena is distinctly different from the color change caused by food. Melena is typically described as being jet-black, having a thick, tar-like consistency, and possessing a foul odor. This characteristic appearance and smell are due to the hemoglobin in the blood being chemically altered by digestive enzymes as it travels through the intestines.
If the black stool lacks the tarry consistency and strong smell, and you can link the change to having eaten cherries, the cause is almost certainly benign. However, if the black stool is tar-like, sticky, and foul-smelling, or if it is accompanied by other symptoms, medical attention should be sought immediately. Warning signs include lightheadedness, dizziness, abdominal pain, vomiting, or unexplained fatigue.
Other Foods and Supplements That Alter Stool Color
Cherries are not the only item that can cause a harmless change in the color of bowel movements. Many other foods and supplements contain dark pigments that are poorly absorbed by the digestive system. For instance, consuming large amounts of blueberries, blackberries, or black licorice can produce a similar darkening effect on the stool.
Certain common over-the-counter medications and supplements also cause this temporary dark coloration. Iron supplements, frequently taken for anemia, can interact with stomach acids and turn the stool a dark green or black color. Medications containing bismuth subsalicylate, like the common antidiarrheal Pepto-Bismol, are another source of pseudomelena. The bismuth reacts with trace amounts of sulfur in the digestive tract to form bismuth sulfide, a black salt that darkens the stool as it passes.