Humans contain about 2-4g iron of which most is in hemoglobin and to a lesser extent myoglobin. Iron from diet is found in heme (animal foods) and nonheme (plant foods) forms. The heme iron needs to be hydrolyzed where as the nonheme is enzymatically freed.
Heme iron is absorbed intact accross the brushborder of the enterocyte whereas nonheme iron is released as ferric in the stomach, which may be reduced to ferrous. The ferric is absorbed across brush border by binding to transporters and the ferrous facilitated by chelators and membrane proteins.Chelators inhibit or enhance absorption of iron. Absorption is also regulated by hepcidin and ferroportin. Other iron-absorption enhancers are sugars, acids, animal meat, and mucin. Other inhibitors are polyphenols, oxalates, phytates, phosvitin and some minerals.Iron is stored in the liver, bone marrow and spleen. Uptake into tissues depends on transferrin.
Iron needs depend on its loss such as through menstrual losses and dietary intake. Deficiency mainly can affect infants and children, teenagers, menstruating females and pregnant women (whose iron needs expand due to increased blood volume). Iron deficiency can develop gradually into anemia. Toxicity may occur due to taking too much iron in supplements or if one has a genetic disorder called hemochromatosis. In the case of hemochromatosis, which is most prevalent among caucasian males, a diet with limited meat intake may be necessary.
