The rapid rate of growth of the brain during the last third of gestation and the early postnatal stage makes it vulnerable to an inadequate diet, although brain development continues into adulthood and micronutrient status can influence functioning beyond infancy. Certain dietary deficiencies during the first 2 years of life, for example iodine and iron, create problems that are not reversed by a later adequate diet. It is important that the intake of micronutrients varies greatly between individuals as they are essential for metabolism in general and in particular cell division and hence growth. In developing countries, there is consistent evidence that the adequacy of diet has lasting implications for cognitive development. In particular, attention has been directed to protein–calorie malnutrition and more specifically the intake of iron, iodine and vitamin A, a deficiency of which damages eyesight. In industrialized countries variations in diet are less influential, although a few well-designed studies have reported that multivitamin and mineral supplementations influence anti-social behaviour and intelligence. In the short term, there is increasing evidence that the missing of breakfast has negative consequences late in the morning. A working hypothesis is that meals of a low rather than high glycaemic load are beneficial.