Iron deficiency without anaemia: Do not wait for the haemoglobin to drop?

Iron is the most common metal in the earthʹs crust yet iron deficiency is the most common nutritional deficiency found in humans. The clinical causes and consequences of iron deficiency anaemia are well established. However, iron deficiency without anaemia is a less well described phenomenon. Here we review the available literature examining the deleterious effects of iron deficiency without anaemia on cognitive development and physical performance. We go on to summarise the available evidence for the effects of iron supplementation on cognition and performance with emphasis of a beneficial effect on performance in heart failure patients.