Elderly people who have black stools may have recently consumed more iron-rich foods, or they may be suffering from diseases such as peptic ulcer, which leads to gastrointestinal bleeding. 1. If the elderly recently consumed more food containing more iron such as spinach, duck blood, or because of the use of some iron supplements, such as ferrous sulfate, etc., iron will be in the gastric acid and intestinal flora under the action of ferrous sulfide, ferrous sulfide is a kind of black material, which will make the stools black. 2. If the elderly themselves have some diseases, such as gastritis, peptic ulcer, gastric cancer, etc., it will lead to gastrointestinal bleeding, the blood into the intestinal cavity, because the blood also contains more iron, so it will also generate black ferrous sulfide, producing black stool. So if the elderly have black stool, you can adjust the diet and observe for a few days, if the black stool persists or worsens, you should go to the gastroenterology department in time and standardize the treatment under the guidance of the doctor.