Iron : An Introduction

The most important role of iron in the body is as an oxygen carrier, in haemoglobin in the red blood cells and myoglobin in muscles. Oxygen is needed for many processes in the body, and is picked up in the lungs by the haemoglobin in the blood flowing through them and carried to the tissues where it is needed. 

However, iron also has many other functions in the body as part of enzyme systems involved in the transfer of energy between cells and in amino acid metabolism. Too much free iron in the body could be dangerous, and the absorption, transport, and storage of iron in the body are closely regulated. Surplus iron is stored in the liver, spleen, and bone

marrow as ferritin (which is readily available when needed) and haemosiderin (an insoluble form). 

Iron deficiency is more common than iron overload and is usually due to loss of blood at a rate greater than that at which it can be absorbed from the diet. In developed countries deficiency is most common in women due to heavy menstrual losses, but in developing countries it may be due to infection with intestinal parasites, and affects both men and women. In the UK there is evidence to suggest that low iron intakes are common in women, with most reporting intakes lower than the recommended nutrient intakes. 

There is a clear association between these low intakes and low haemoglobin and ferritin levels. Iron is present in the diet in two forms: haem iron in meat and non-haem iron (inorganic salts) in plants. Haem iron is absorbed most efficiently, but if animal products are present in the diet they also seem to enhance non-haem iron absorption, possibly due to the presence of specific amino acids. 

The absorption of non-haem iron is also facilitated by having a source of vitamin C at the same meal orange juice with the cereal at breakfast, for example and by some organic acids. Dietary fibre and phytates associated with this hinder absorption of iron, as do concurrent high calcium intakes and tea. People in groups with a high risk of iron deficiency could possibly maximize absorption of iron by not drinking tea or milk at mealtimes.