Iron is the most abundant trace mineral in the body, and iron deficiency anaemia is the most prevalent Worldwide deficiency. Iron is required by mammals for haemoglobin synthesis and as a cofactor to a number of hydroxylase enzymes involved in neurotransmitter synthesis. The most important source of iron in the diet in red meat, However, plants also provide iron. In animal protein the iron is bound to proteins such as myoglobin and haemoglobin. The iron in plants is also bound to proteins, but the proteins and the form of iron are different. In this regard the iron is more tightly bound to the proteins, and the iron is in a more oxidised state. Animal protein is a much more bioavailable source of iron for this reason. Most of the World obtains most of its iron from plant sources and this may explain the high Worldwide prevalence of iron deficiency anaemia compared to other mineral deficiencies. However, this is a controversial opinion as iron deficiency anaemia is still common in Western nations where animal protein is consumed.
Deficiency of iron is well characterised, but less is reported on the dangers of too much iron. Increasing iron intakes beyond that required can have two possible effects. Firstly the excess iron can inhibit the absorption of other trace minerals such as zinc, and secondly there is a possibility that excess iron could increase the generation of free radicals. Iron concentrations in animal and plants tissues are low, and this is because iron is very insoluble in water, and in its free form, iron can participate in the generation of free radicals. For these reasons both plants and animals bind iron to proteins and this allows the transport of iron in the watery medium of the blood or plant vasculature while at the same time preventing the generation of free radicals. Increases in intracellular or extracellular free iron, that can result from protein deficiency, cellular injury, iron loading or deficiencies of binding proteins, can therefore significantly increase free radical generation and the risk of certain diseases related to the generation of free radicals.
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