Deficiency diseases result from insufficient amounts of various healthful nutrients in the diet. Examples include scurvy, caused by a deficiency of vitamin C, or ascorbic acid; pellagra, caused by a deficiency of niacin; and osteoporosis, caused at least in part by a lack of calcium. Deficiency diseases are most prevalent in poverty- or war-stricken areas of the world, where malnutrition is widespread. Deficiency diseases are also found in more affluent nations where food is prevalent but people’s food choices or behavior do not provide well-rounded nutrition, resulting in such disorders as anorexia nervosa, bulimia, and anemia.