The effects of iron supplementation on cognitive function in infants and children.

Iron deficiency and iron deficiency anaemia are still the most common nutritional disorders worldwide, predominantly affecting women of child-bearing age and infants and young children. In 1985, De Maeyer and AdielsTegman [1] collated data from studies which had looked at the prevalence of anaemia over the preceding 20 years. For preschool children, the prevalence of anaemia was estimated at 51% in developing countries and 10% in developed countries. In the USA, with the implementation of the Special Supplemented Food Program for Women, Children and Infants (more commonly referred to as the WIC program), anaemia has been reduced from 8%, in children under 5 years of age, to 3.1% [2]. These figures however could not distinguish between anaemia due to iron deficiency and anaemia from other causes. More recent figures from the UK show a prevalence of iron deficiency anaemia of 8% in children under 4 years, but up to 12% in children under 36 months [3]. Lack of iron in the diet for the first 2 years of life could theoretically be important for development as this is the time when the majority of brain growth occurs. Although the most rapid brain growth is seen in the months leading up to birth, at birth itself the brain has only reached 27% of its adult size and it continues to grow for the next 2 years [4]. Iron levels in the brain at birth have been shown to be 10% of eventual adult levels [5], with the remainder accumulating through childhood. As a component of haemoglobin the major role of iron is concerned with oxygen transport, but iron is also an essential component or cofactor for many enzymes including haem enzymes in the mitochondria and iron-dependent enzymes such as the flavoproteins. It also acts as a cofactor for several enzymes