Nutrition and cognition: how big a difference does it make?

There has been an emphasis on the importance of nutrition during the last third of pregnancy and the first two years of life when the brain develops rapidly, with various suggestions that inadequate nutrition at this stage can have long-term consequences. It is generally accepted that during brain development a shortage of iodine or iron can have long-term negative effects (Benton, 2008). More generally higher body weight at birth, thought to reflect the mother’s nutrition, has been related to intelligence in later life (Richards et al., 2001). Some of the best data have been obtained from premature infants who randomly were allocated to a standard cows-milkbased formula or one enriched with protein, vitamins and minerals. The enriched formula resulted in higher intelligence scores in boys (Lucas et al., 1998) who at fifteen years boys had a larger caudate nucleus, as measured using MRI (Isaacs et al., 2008). Such data strongly suggest that the nature of early nutrition can have long-term consequences. In this context we are only beginning to consider the optimal nature of diet, although recent epidemiological data have associated a higher consumption of fish during pregnancy by the mother, with higher intelligence in children at eight years (Hibbeln et al., 2007). Food intoleranceis another way in which behaviour can be adversely influenced over a long period. Benton (2007) used meta-analysis to review the use of an oligoantigenic diet (few foods) in children with a history of hyperactive symptoms. In five well controlled studies the standardized mean difference was 0.80 of a standard deviation (95% CI 0.41 to 1.19); there were significantly fewer symptoms of hyperactivity when the children consumed a placebo meal than when they ate what for them was a problem food. The responses were idiosyncratic with several dozen foods proving to be a problem. The findings should not be uncritically generalized to other groups as these were studies of children whose parents prior to the study suspected that food may be a problem.