The best known is beetroot. Often times people think they have blood in their stool and then they come in and we test their stool and find that there is no blood. If I ask, “Did you have a beet salad two or three days ago?” They will realize that they forgot and everything is fine. Algae are a surprising new thing – people eat a ton of algae snacks, which can cause fluorescent green feces.
Pepto-Bismol also changes the color of the chair to black. Black stool, which is sticky and tarry, is an indicator of upper gastrointestinal bleeding because when blood is digested it turns black. But some people may forget they took Pepto-Bismol, see the black stool, and worry about an ulcer. The way to differentiate is this: if you take Pepto-Bismol and then you have hard, black, pebbly bowel movements, it’s probably just the Pepto-Bismol, but if you take a lot of aspirin and then you have a stomach ache along with tarry black stool that smells , it is likely an ulcer bleeding. In this case, you should see a doctor about the blood. Iron supplements can also cause black stools, but this one will appear black and grainy instead of black and sticky.
If you have pain in the upper right side of your abdomen, like a gallstone attack, and have pale, white, or manila colored stools, it may mean that your bile ducts are blocked and you should see a doctor. Gray stool is an indicator of a pancreatic problem. If your urine is dark and your stool is light, it could be a pancreas problem or a bile duct problem.
Red stools can indicate hemorrhoids, fissures, or deeper gastrointestinal disorders such as ulcerative colitis, Crohn’s disease, colon polyps, or cancer. Red stools must be examined with a colonoscopy.