Non-anaemic Iron Deficiency

Iron balance is regulated by absorption of iron rather than by excretion, because humans cannot actively excrete iron. Iron is absorbed from the small intestine. The regulation of iron absorption and transport is complex; there seems to be an important role for hepcidin, a hormone secreted by the liver. Iron is lost from the body through sloughed skin cells and sloughed enterocytes from the gut, and through any form of blood loss. A mature fetus has iron stores, which are required because breast-feeding does not meet the infant's iron requirements. Low birthweight babies lack this store. Iron requirements increase at times of growth (early childhood and adolescence); during pregnancy and with menstruation. Dietary iron is in two forms, haem iron (the organic form, mainly found in meat) and non-haem iron (the inorganic form, mainly from plants). Haem iron is much better absorbed. Non-haem iron absorption can be improved by meat and ascorbic acid (vitamin C). Absorption is inhibited by calcium, phytates (in some plant foods) and polyphenols (in tea and coffee). Iron is present in many foods, so iron intake is partly related to calorie intake.