Nutritional disorders

Nutritional disorders may be caused by a deficiency or excess of one or more nutrients, or by the presence of a toxin (poisonous element) in the diet. A diet deficient in carbohydrates is almost inevitably also deficient in protein, leading to the development of protein–calorie malnutrition. Such malnutrition is most often seen as a result of severe poverty and famine (see kwashiorkor; marasmus). Deficiency of specific nutrients is commonly associated with a disorder of the digestive system, such as coeliac disease, Crohn’s disease, or pernicious anaemia (see anaemia, megaloblastic). Inadequate intake of protein and calories may also occur in people who excessively restrict their diet to lose weight (see anorexia nervosa), hold mistaken beliefs about diet and health (see food fad), or suffer from a loss of interest in food associated with alcohol dependence or drug dependence. Obesity results from taking in more energy from the diet than is used up by the body. Nutritional disorders may also result from an excessive intake of minerals and vitamins. An excessive intake of saturated fat is thought to be a contributory factor in coronary artery disease and in some forms of cancer. Naturally occurring toxins can interfere with the digestion, absorption, and/or utilization of nutrients, or can cause specific disorders due to their toxic effects: for example, the ergot fungus found on rye can cause ergotism.