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).
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.
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.
Upper safe level for daily
supplementation = 15mg
Recommended Daily Allowance = 14mg
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.
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 (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.
Related News Stories
Scientists suggest that aspirin use
may be a cause of anaemia in the elderly.
Australian research into iron levels
in vegetarian males reveals lower levels than in meat-eating
males.
Investigations into the potentially
negative side effects of taking the ferrous sulphate form of
iron supplements.
Possible links between childhood
intakes of iron and its long term effects on learning.
Different sorts of iron supplement
may affect absorption levels in different people.
An American study reports iron loss
in adolescent girls, which supports supplementing with iron at
this stage.
A study of women in the developed
world show iron intakes below the RDA.
Research supports that iron
supplementation may help eliminate the dry cough, which is a
side effct of taking ACE inhibitor drugs.
Deficiencies in certain nutrients
may have links to complications in pregnancy.
