Iron

What it does

Iron's most important role is carrying oxygen. It sits at the centre of haemoglobin, the pigment in red blood cells that picks up oxygen in the lungs and releases it throughout the body, and of myoglobin, which stores oxygen in muscle. Because almost every cell needs oxygen to release energy, a shortage of iron quickly leads to tiredness, breathlessness and pallor — the classic picture of iron-deficiency anaemia.

Beyond oxygen transport, iron is a component of many enzymes involved in energy production, DNA synthesis and the normal working of the immune system. It also plays a part in normal brain development and function, which is one reason iron deficiency in infants and young children is taken so seriously. The body has no active way to excrete excess iron, so it carefully controls how much it absorbs.

Dietary iron comes in two forms: haem iron from meat and fish, which is well absorbed, and non-haem iron from plants such as pulses, wholegrains and green vegetables, which is absorbed less efficiently. Vitamin C taken in the same meal boosts absorption of the plant form, while tea, coffee and calcium can reduce it. Requirements are higher for menstruating women, during pregnancy and for growing children, making these the groups most prone to deficiency.