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.
When related to foods, blueberries, beets, or black licorice are often the cause. Stool passed after eating these foods may be dark brown, bluish, reddish, or black. Iron supplements and medications containing bismuth subsalicylate, a common ingredient in anti-diarrhea medications, can also turn the stool dark or black. Dark stool not associated with specific foods or medications can be more worrisome and may be an indicator of bleeding somewhere in the digestive system. The color and quality of the stool depends on where the bleeding is occurring and how fast the stool moves through the digestive system.