Various types of potatoes. A staple food, or simply a staple, is a food that is eaten routinely and in such quantities that it constitutes a dominant portion of a standard diet for a given people, supplying a large fraction of energy needs and generally forming a significant proportion of the intake of other nutrients as well.
Constipation is defined medically as fewer than three stools per week and severe constipation as less than one stool per week. Constipation usually is caused by the slow movement of stool through the colon.
However, black stool can also be caused by a serious condition, such as bleeding in the digestive tract caused by a peptic ulcer. Black stool that is tarry in texture and foul smelling is often a symptom of upper gastrointestinal bleeding from the esophagus, stomach or small intestine. This is called melena. Rectal bleeding of bright red blood with clots, sometimes mixed with stool, is called hematochezia.