Iron is the most important transitional metal in the body, as it is implicated 
in many metabolic processes, mostly related to its capacity as an electron 
donor/acceptor. Iron deficiency has been long been known to cause anaemia, iron 
excess to cause haemochromatosis. As excess free iron can cause oxidative 
damage, it is important that the levels of iron in the body are tightly 
regulated which appears to be done only by digestive absorption, as there is no 
known regulating mechanism for elimination of iron. The amount of free iron is 
also kept to a minimum thanks to binding to transferrin for transport, and to 
ferritin for storage. Recent research has put emphasis on the possible role of 
excess iron in the brain in several degenerative diseases. Iron deficiency in 
the central nervous system is known to cause motor impairment and cognitive 
deficits; more recently, it has been suggested that it may play a role in the 
pathophysiology of the restless leg syndrome. 2001 Harcourt Publishers Ltd