If you eat a lot of purple potatoes for a long time, you will have black stools. Purple potatoes belong to sweet potato food, which contains a lot of starch, and rich in fiber, after eating a lot of purple potatoes can replenish the body’s need for sugar, replenish the body’s need for energy, the cellulose content can promote gastrointestinal peristalsis, to promote gastrointestinal contents of the digestion and absorption, to promote the discharge of the stools, because of purple potatoes for the purple food, if the patient’s diet is too much, and long term consumption, there will be a purple-black stools. If the patient eats too much and consumes it for a long time, the stool will be purple-black. If the patient eats only a small amount of purple potatoes, then black stools, this time need to be vigilant about gastritis, gastric ulcer and other upper gastrointestinal bleeding may be, it is recommended to complete the routine stool examination, to clarify whether the occult blood is positive, and to be handled accordingly.