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.
Dark stool is caused by upper GI tract bleeding. Generally, we get concerned when we see blood or red-tinged feces, but dark, tarry stool can indicate that something is wrong and is as much of a concern as red, obviously bloody stool. Tarry, black stool is called melena, and it is often foul smelling.