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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.
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