Iron is a trace element essential for life. It is found in the body in red blood pigment, muscle protein and numerous enzymes. In red blood cells, it transports oxygen, and iron also plays a role in energy production and the manufacture of numerous important substances. Iron is primarily involved in the processes in which oxygen plays a role: it is needed for oxidation processes and thus energy production in the cell and cell respiration, is responsible for oxygen storage in myoglobin, the red muscle pigment, and – bound to hemoglobin, the blood pigment of red blood cells – for transporting oxygen in the blood to the cells. In addition, iron is involved in the formation of various enzymes.
Iron in hemoglobin
Dietary iron is absorbed mainly as trivalent iron in the small intestine, although the functioning of the transport system also depends on gastric acid and is easily disrupted by various factors (for example, ingredients of tea and coffee, drugs, calcium). Only a limited amount of iron of about five milligrams can be absorbed daily.
To keep losses as low as possible, iron does not occur freely in the blood but is bound to protein molecules, for example haptoglobin and ferritin. About 70 % of the iron in the body (in adults a total of four to five grams) is found in hemoglobin, the rest in the liver, spleen, intestinal mucosa and bone marrow. Natural losses occur primarily through skin desquamation and exfoliation of cells on the gastrointestinal mucosa; in women, a not insignificant amount is added by blood loss during menstruation.
Recommended daily dose of iron
The recommended daily dose of iron is ten milligrams for men and 15 milligrams for women (of childbearing age). This daily dose of iron is found in, for example.
- 100 g pork liver
- 150 g sesame
- 200 g wheat germ
- 200 g legumes
- 350 g nuts
- 350 g wholemeal flour
- 400 g spinach
- 750 g muscle meat
Iron in food
Iron is found in both plant and animal foods, for example, green leafy vegetables, nuts, cereals and meat. However, the body can better utilize the iron contained in animal products. The simultaneous intake of vitamin C (for example, in orange juice) can increase the absorption of iron in the intestine. Calcium, phosphorus, and substances in black tea and coffee worsen iron absorption from food.
