malnutrition, insufficiency of one or more nutritional elements necessary for health and well-being. Primary malnutrition is caused by the lack of essential foodstuffs—usually vitamins, minerals, or proteins—in the diet. In some areas of the world a poor economy or such regional conditions as drought or overpopulation cause a scarcity of certain foodstuffs, and a certain portion of the population is malnourished because essential nutrients are not available. However, even when food is plentiful, malnutrition can result from poor eating habits or poverty. Primary malnutrition, due to a lack of food or an inability to afford nutritious food, has been estimated to affect as many as a fourth of the world's children. Secondary malnutrition is caused by failure of absorption or utilization of nutrients (as in disease of the gastrointestinal tract, thyroid, kidney, liver, or pancreas), by increased nutritional requirements (growth, injuries, burns, surgical procedures, pregnancy, lactation, fever), or by excessive excretion (diarrhea).