Iron is an essential nutrient that performs a wide range of functions in the body, including assisting in the transport of oxygen via the blood.
Iron is an essential part of haemoglobin, a substance inside red blood cells that is designed to carry oxygen around the body. It is also used to form myoglobin, which is similar in function to haemoglobin and delivers oxygen to skeletal muscles. Iron is also an essential part of many enzymes. Enzymes are substances that speed up chemical reactions within the body. Iron is a component of the enzymes that break down drugs and other foreign, potentially toxic chemicals before they can be excreted by the body. Excess dietary Iron intake is toxic and causes vomiting, diarrhoea and damage to the intestines. The genetically inherited disease haemochromatosis is characterised by excess absorption of Iron from the intestines. It can cause tissue damage as the excess Iron is deposited in the body organs.
Iron deficiency is the most common nutritional deficiency in the world. It can be caused by inadequate dietary Iron intake, deficiencies in the ability to absorb iron or by blood loss. The symptoms and signs of Iron deficiency include iron deficiency anaemia, where the red blood cells are abnormally small and pale and have a low content of haemoglobin. This can cause pallor, fatigue, breathlessness on exertion, palpitations, dizziness and headache. Other signs include cracks in the corners of the mouth, sore tongue and brittle fingernails. Often there are no symptoms and the deficiency may be discovered during routine blood tests. Vague symptoms of tiredness are common. Iron deficiency in young children can cause behavioural problems such as reduced attention span and reduced cognitive performance that may be irreversible.
There are two nutritional forms of Iron: haem Iron and non-haem Iron. The body much more easily absorbs Haem Iron than non-haem Iron, although the absorption of non-haem Iron can be improved when food is eaten with vitamin C and protein. Sources of haem Iron include meat, poultry and fish. Non-haem iron is found in cereals, vegetables, pulses, beans and fruit. Other substances that are present in foods can decrease the amount of non-haem Iron that the body absorbs. These substances include calcium, soy products and phytates (found in all grains, seeds, nuts, vegetables and fruit). Substances called tannins, which are found in tea, coffee and cocoa, also inhibit Iron absorption. Tea and coffee should not, therefore, be consumed with a meal as they strongly decrease the amount of Iron absorbed from the food.
Iron is a component of many dietary supplements, where it is usually in the form of what is called 'ferrous' iron. The other form that Iron can exist in is 'ferric' iron. Ferrous and ferric are terms used to describe the positive charge that Iron has. Ferrous Iron is the form of Iron that is best absorbed by humans.
The recommended dietary intake (RDI) for Iron is 7 mg per day for adult males and 12-16 mg per day for adult females, although women that are pregnant require and additional 10 to 20 mg per day.