The nutritional need for iron in living organisms is derived from the central role that it plays in the energy metabolism of living cells. However, iron exists in almost exclusively in the less soluble oxidised state (Fe III). This has greatly reduce its accessibility. Iron in foods exist in two main forms: haem iron and non-haem iron, which are absorbed by different pathways with different degrees of efficiency depending upon dietary and physiological factors. All these factors increase or reduce the proportion of the total iron in a food or diet that is utilised for metabolism, that is iron bioavailability. Iron deficiency leads to anaemia, one of the most common nutritional deficiency disorders in the world both in industrialised and developing countries. Preventing this illness is based on a gradual growth in our understanding of iron nutrition.