Thus, dietary iron absorption and factors affecting bioavailability in the body are tightly regulated where possible. Excess ferrous iron forms free hydroxyl radicals via the Fenton reaction that cause damage to tissues through oxidative reactions with lipids, proteins, and nucleic acids. Iron overload can be particularly damaging to the heart, liver, and endocrine organs. Human enterocytes contain apical membrane-bound enzymes whose activity can be regulated and which function to reduce insoluble ferric (Fe3+) to absorbable ferrous (Fe2+) ions.Īlthough iron deficiency is a relatively common problem, it is not the only extreme of the iron-balance spectrum that must be avoided. One reason for the lack of adequate iron absorption is that upon exposure to oxygen, iron forms highly insoluble oxides, which are unavailable for absorption in the human gastrointestinal tract.
Low intake of iron accounts for most anemia in developed countries and is responsible for nearly half of the anemias in non-industrialized nations. Non-heme iron is derived from plants and iron-fortified foods and is less well absorbed.ĭespite its relative abundance in the environment and the relatively low daily iron requirements (10 mg ingested/1 mg absorbed) of humans, iron is often a growth-limiting nutrient in the human diet. Iron chelators treat iron overload, a condition often caused by transfusion therapies used to treat thalassemias and other anemias. Īdditionally, approximately 2.2% of total body iron is found in the so-called labile pool, a poorly defined and reactive pool of iron that forms reactive oxygen species via the Fenton Reaction, which forms complexes with a drug class known as chelators. Iron is also found bound to proteins (hemoprotein) and non-heme enzymes involved in oxidation-reduction reactions and the transfer of electrons (cytochromes and catalase). In the human body, iron exists mainly in erythrocytes as the heme compound hemoglobin (approximately 2 g of iron in men and 1.5 g in women), to a lesser extent in storage compounds (ferritin and hemosiderin) and in muscle cells as myoglobin. The mechanism of iron excretion is an unregulated process arrived at through loss in sweat, menstruation, shedding of hair and skin cells, and rapid turnover and excretion of enterocytes. Unlike other minerals, iron levels in the human body are controlled only by absorption.
Iron is an essential element of various metabolic processes in humans, including DNA synthesis, electron transport, and oxygen transport.
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