Iron is an essential
component of haemoglobin, transporting oxygen in the blood to all parts
of the body. It also plays a vital role in many metabolic reactions.
Iron deficiency can cause anaemia resulting from low levels of haemoglobin
in the blood. Iron deficiency is the most widespread mineral nutritional
deficiency both in Britain and worldwide.
Functions
Iron
is essential for the formation of haemoglobin, the red pigment
in blood. The iron in haemoglobin combines with oxygen and transports it
through the blood to the body's tissues and organs. The body contains between
3.5 and 4.5g of iron, 2/3 of which is present in haemoglobin. The remainder
is stored in the liver, spleen and bone-marrow. A small amount is present
as myoglobin, which acts as an oxygen store in muscle tissue.
Iron deficiency can lead to
anaemia. Iron stores in the body become depleted and haemoglobin synthesis
is inhibited. Symptoms of anaemia include tiredness, lack of stamina,
breathlessness, headaches, insomnia, loss of appetite and pallor. All
these symptoms are associated with decreased oxygen supply to tissues
and organs. Iron also plays an important role in the immune system,
people with low iron levels having lowered resistance to infection.
Research has also shown iron deficiency to be associated with impaired
brain function, and iron deficiency in infants can result in impaired
learning ability and behavioural problems.
Iron deficiency is the most
prevalent nutritional problem both in Britain and worldwide. It has
been stated that 2/3 of children and women of child-bearing age in
developing countries suffer from iron deficiency, 1/3 suffering from
severe deficiency and anaemia. In developed countries, between 10-20%
of child-bearing age women are said to be anaemic. Iron is the least
plentiful nutrient in the typical British diet and anaemia is fairly
common in the UK.
Dietary Sources
Dietary
iron exists in two different forms. Haem iron only exists in animal tissues,
whilst in plant foods iron is present as non-haem iron. In a mixed omnivore
diet around 25% of dietary iron is non-haem iron. Non-haem iron is less
easily absorbed by the body than is haem iron. The amount of iron absorbed
from various foods ranges from around 1 to 10% from plant foods and 10
to 20% from animal foods.
The absorption of iron is influenced
by other constituents of a meal. Phytates, oxalates and phosphates
present in plant foods can inhibit absorption, as can tannin in tea.
Fibre may also inhibit absorption. Vitamin C greatly increases the
absorption of non-haem iron. Foods rich in vitamin C include citrus
fruits, green peppers, and fresh leafy green vegetables. Citric acid,
sugars, amino acids and alcohol can also promote iron absorption. Iron
absorption can also be influenced by the amount of iron in the diet.
Lowered levels of iron in the diet result in improved absorption.
Good sources of iron for vegetarians
include wholegrain cereals and flours, leafy green vegetables, blackstrap
molasses, pulses such as lentils and kidney beans, and some dried fruits.
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