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.
There are many reasons that stools could appear black or tarry with a foul smell, including eating certain foods or taking iron supplements. However, black stools can also be a result of bleeding, and the darker color indicates that the blood could be coming from a point in the upper gastrointestinal tract. When stools are black or tarry due to blood being present, it is called melena..