Iron: keeping blood healthy
BMJ 2002; 324 doi: https://doi.org/10.1136/sbmj.0204100 (Published 01 April 2002) Cite this as: BMJ 2002;324:0204100
- Sarah Schenker, dietician1
- 1British Nutrition Foundation, London
The body has a requirement for iron because of the central role that it plays in energy metabolism and in the production of red blood cells (erythropoesis). Iron is a transition metal and takes part in redox processes--for example, reduction by an organic substrate and reoxidation by oxygen. It binds with oxygen either on its own or as part of a complex. Iron is transported in the blood by the protein transferrin and is stored in the body as the proteins ferritin and haemosiderin. Functionally important forms of iron are haemoglobin, myoglobin, cytochromes, iron-sulphur proteins, iron enzymes, and lactoferrin.
Where is iron found in the body?
Approximately two thirds of the body's iron is in the pigment haemoglobin, which transports oxygen in red blood cells. Most of the 20-30 mg of iron needed each day for the synthesis of haemoglobin comes from the recycling of senile red blood cells. Red blood cells live for 120 days before their constituents are reprocessed: iron is recycled in the body maintaining a constant internal supply independent of diet.
Senile red blood cells are destroyed by macrophages in the spleen. Transferrin takes up the released iron and carries it to the bone marrow. Developing red blood cells remove this iron and incorporate it into haemoglobin. The body has no active mechanism to excrete unwanted iron, so little iron is lost from the body.
How much iron do we need?
Men lose about 1 mg of iron each day through sweating and shedding epithelial cells from the skin, intestine, and genitourinary tract. Women lose more iron because of menstruation: about 2 mg each day. Because obligatory loss …
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