Iron is critical for the function of a number of physiological processes (details )
Iron is recycled and thus conserved by the body. Daily intake ( 1 mg ) s balanced against small daily losses (1 mg ). Most of the body iron is part of the hemoglobin molecule where iron serves a key role in oxygen transport.
The amounts shown in the Fe Cycle Card are in mg of iron lost or gained per day. They were derived in the following manner.
The average blood volume in a 70 kg man is 5,000 ml.
There are 150 grams of hemoglobin in each liter of blood, therefore there are 750 g of hemoglobin in the body.
Each gram of hemoglobin contains approximately 3.3 mg of iron or 2475 mg of iron in the body.
Dividing the 2475 mg total by the 120 day average RBC lifespan results in the iron needed per day or 20.6 mg iron/day.
***
| Protein | mg |
| Hemoglobin | 2200 |
| Ferritin & Hemosiderin | 1000 |
| Myoglobin | 300 |
| Others | 100 |
| Total Body Iron | 3600 |
***
Iron uptake
An average adult in the U.S. on a 2,500 calorie diet ( 6 mg of iron/1,000 kcal) ingests 15 mg of iron daily. Only 5-10 % or about 1.0 mg of dietary iron is absorbed as ferrous iron (Fe++), mainly in the duodenum and upper jejunum where the pH is low. The mucosal cells oxidize the ferrous iron to ferric iron , which is then complexed with apoferritin to form ferritin. Some of the ferritin is transported out of the mucosal cell into the plasma bound to transferrin. Thus bound, iron can be transported to the bone marrow or iron storage sites where it is stored as either ferritin or hemosiderin.
Iron distribution
Although iron is utilized in virtually all cells, the bulk of body iron is found in erythrocytes with lesser amounts in myoglobin. Large amounts of iron are required during growth periods in infant, childhood and teenage years.
Not all erythrocytes develop and mature successfully. Some die in the marrow and their iron is salvaged by macrophages. This failure to mature resulting in death in the marrow is known as ineffective erythropoiesis.
Iron loss
Normally only small amounts of iron are lost daily as hair, skin, urinary bladder,and gastrointestinal cells are shed. This amount can easily be replaced by dietary intake.
With bleeding, larger amounts of iron can be lost. The most common normal blood losses are due to menstruation and pregnancy.
Mutations in genes involved in iron metabolism can heavily modify the pattern of iron distribution
Genetic regulation of cell function in response to iron overload or chelation. 2003
Two to Tango: Regulation of Mammalian Iron Metabolism, 2010
