Human iron metabolism: Difference between revisions
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'''Iron''' is an essential nutrient for human beings, although it can also be toxic. The most important role is in the [[heme]] protein of [[hemoglobin]], | '''Iron''' is an essential nutrient for human beings, although it can also be toxic. The most important role is in the [[heme]] protein of [[hemoglobin]] and [[cytochrome P-450]], and secondarily for [[myoglobin]], which transports oxygen into muscle cells. Iron also is a component of a number of enzymes. | ||
==Requirements== | |||
The actual requirement for iron in food is quite low, as most of the total iron in the body is recycled from [[ferritin]], a protein carrier of the metal. | |||
==Digestion== | |||
Iron, in food, is processed differently depending if it is in the form of heme (e.g., in meats) or in other molecules. As food breaks down in the [[stomach]], ferric (Fe<sup>+3</sup>) iron is reduced to ferrous (Fe<sup>+2</sup>) iron by the enzyme [[ferric reductase]]. [[Ascorbic acid]], a reducing agent, is a cofactor for absorption. | |||
Non-heme iron, however, may not be available to the digestive processes. While [[spinach]] is legendary as an iron source, the iron in raw spinach is bound into a non-absorbable [[oxalic acid|oxalate]]. Cooking the spinach does make the iron bioavailable; the cartoon character [[Popeye the Sailor Man]] was correct in eating his spinach from a can. | |||
Most actual absorption takes place in the [[duodenum]]. Heme is absorbed via the [[heme transporter]] protein. Non-heme iron enters the apical surface of the [[enterocyte]]s lining the duodenum via [[divalent metal transporter 1]] (DMT1)<ref>{{citation | |||
| date = Advance Access originally published online on August 25, 2005 | |||
| journal = Human Reproduction | |||
| url = http://humrep.oxfordjournals.org/cgi/content/full/20/12/3532 | |||
| volume = 20| issue = 12 | pages = 3532-3538 | |||
| year = 2005 | |||
| author = Chong WS ''et al.'' | |||
| doi=10.1093/humrep/dei246 | |||
| title = Expression of divalent metal transporter 1 (DMT1) isoforms in first trimester human placenta and embryonic tissues}}</ref>, carrying iron into the [[interstitial fluid]] by a protein called [[ferroportin]] (FP). | |||
==Distribution== | ==Distribution== | ||
Ferrous iron, in plasma, is reconverted to ferric, and bound to a carrier protein, [[ferritin]]. | |||
==Excretion== | ==Excretion== | ||
==Disorders of iron metabolism== | ==Disorders of iron metabolism== | ||
==References== | |||
{{reflist}} | |||
Revision as of 18:08, 2 January 2010
Iron is an essential nutrient for human beings, although it can also be toxic. The most important role is in the heme protein of hemoglobin and cytochrome P-450, and secondarily for myoglobin, which transports oxygen into muscle cells. Iron also is a component of a number of enzymes.
Requirements
The actual requirement for iron in food is quite low, as most of the total iron in the body is recycled from ferritin, a protein carrier of the metal.
Digestion
Iron, in food, is processed differently depending if it is in the form of heme (e.g., in meats) or in other molecules. As food breaks down in the stomach, ferric (Fe+3) iron is reduced to ferrous (Fe+2) iron by the enzyme ferric reductase. Ascorbic acid, a reducing agent, is a cofactor for absorption.
Non-heme iron, however, may not be available to the digestive processes. While spinach is legendary as an iron source, the iron in raw spinach is bound into a non-absorbable oxalate. Cooking the spinach does make the iron bioavailable; the cartoon character Popeye the Sailor Man was correct in eating his spinach from a can.
Most actual absorption takes place in the duodenum. Heme is absorbed via the heme transporter protein. Non-heme iron enters the apical surface of the enterocytes lining the duodenum via divalent metal transporter 1 (DMT1)[1], carrying iron into the interstitial fluid by a protein called ferroportin (FP).
Distribution
Ferrous iron, in plasma, is reconverted to ferric, and bound to a carrier protein, ferritin.
Excretion
Disorders of iron metabolism
References
- ↑ Chong WS et al. (Advance Access originally published online on August 25, 2005), "Expression of divalent metal transporter 1 (DMT1) isoforms in first trimester human placenta and embryonic tissues", Human Reproduction 20 (12): 3532-3538, DOI:10.1093/humrep/dei246