Iron

Description

Iron is also a very important mineral in human physiology, but is in fact only a trace mineral in terms of concentration in the body. (The body contains approximately 4-5g).

Functions

The main function of iron in the diet is as an important constituent of the blood pigment haemoglobin. Haemoglobin is contained within red blood cells and is the carrier of vital oxygen around the body. Other than its function in red blood cells, iron is also found in myoglobin (the equivalent of haemoglobin found in muscle) and is additionally a participant in energy-releasing reactions of the body.

Deficiency

The classical iron deficiency disease is Anaemia. The symptoms of this condition are Fatigue, light-headedness, weakness, etc. accompanied with a correspondingly low haemoglobin measurement in the blood.

Requirements

Upper safe level for daily supplementation = 15mg

Recommended Daily Allowance = 14mg

Supplemental Uses

Women of childbearing age are at the most risk of iron deficiency because of their monthly menstrual blood losses. The RDA does not take into account those women with high menstrual losses, who are advised to meet their extra needs with a supplement (1).

Other people who may need an iron supplement include vegetarians, pregnant women, adolescents, athletes and the elderly (1).

Children may also be deficient in iron, as studies around Britain have shown. In Bradford, 12% of white and 28% of Asian children were anaemic, and in Birmingham 26% of 470 children aged 6 months to 6 years were anaemic(2).

A multivitamin and mineral supplement containing iron in a suitable balance with other nutrients is to be recommended for children, but iron at higher levels should not be taken by children except under medical advice.

Safety

Most cases of iron toxicity have involved accidental iron overload in children. Levels of 20mg per kg bodyweight cause acute toxic symptoms in infants and at ten times higher, iron may be fatal. In adults a 100g dose of iron is lethal unless appropriate antidote treatment is given.

Interactions and Contra-Indications

Iron Binding Drugs:
Certain drugs may bind with iron and cause reduced bioavailability of both the mineral and the drug. These medicines include tetracycline and its derivatives, penicillamine, levodopa, methyldopa and cardidopa.

Iron Binding Foods:
Certain food components also bind with iron (and other minerals) making them unavailable. These include phytic acid found in bran and other fibre foods, and oxalic acid found in Rhubarb , spinach and chocolate.

Vitamin C & B Complex:
One of the most important dietary promoters of non-haem iron absorption is Vitamin C . There is a close relationship between the amount of non-haem iron absorbed and the Vitamin C content of the diet. Iron absorption and utilisation is highly dependent upon the presence of Vitamin C and certain members of the B complex. The mineral Molybdenum is also important in iron metabolism.

Food Sources

Food (mg/100g)
Curry powder 29.6
Fortified breakfast cereal 16.7
Lamb’s liver 7.5
Pig’s kidney 6.4
Apricots, dried 4.1
Bread, wholemeal 2.7
Corned beef 2.4
Chocolate, plain 2.4
Eggs 2.0
Beef 1.9
Watercress 1.6
Bread, white 1.6
Cabbage 0.6
Red wine 0.5
Fish, white 0.5
Potatoes 0.4

The main sources of iron in the diet are meat, bread, cereal products and potatoes. Animal sources of iron are much better absorbed than plant sources, because in animal tissue the iron is organically bound as haemoglobin. In plants, iron is present as the much more poorly absorbed inorganic structure.

References

1. Cook JD. Iron deficiency Anaemia. Baillieres Clin Haematol, 7;4:787-804, 1994.
2. "Dietary Reference Values for Food, Energy and Nutrients for the United Kingdom", Dept. of Health, HMSO, 1991.