The long chain polyunsaturated fatty acids (LCPUFA) arachidonic acid and docosahexaenoic acid (DHA) are predominant in the central nervous system. Neuronal synapses and photoreceptors in the retina are particularly rich in DHA. These fatty acids are available preformed in the diet of omnivores and can be produced through the elongation and desaturation of their parent fatty acids linoleic acid (LA 18:2 n-6) and α-linolenic acid (ALA 18:3 n-3), respectively. However, the ability of neonates to perform these interconversions in sufficient amounts, especially the conversion of ALA to DHA, has been questioned, since late fetal life and infancy are periods of maximal brain growth and demand for these fatty acids is high. This has led to several studies evaluating the effect of postnatal supplementation, both in neonates and older children, particularly with DHA. Despite numerous studies, including several fairly large randomised trials, LCPUFA supplementation of infant formula has not been proved to have beneficial effects on cognitive outcome.1 Studies of LCPUFA supplementation in older children are fewer in number, and confined to children with learning or behavioural disorders. Nevertheless, in some cases claims have been made about the beneficial effects on child development in the absence of sufficient data. For example, the “clever milk” campaign mounted by St Ivel in 2006, had to be withdrawn following complaints to the Advertising Standards Agency.2

Recommendations from official bodies suggest that n-3 fatty acids should be obtained by consumption of foods rich in n-3 fatty acids as part of a balanced diet rather than from supplementation. During pregnancy, a weekly intake of one to two portions of fatty fish is advocated in the UK3 ,4 and elsewhere,5 the aim being to achieve 200–300 mg DHA/day.6 While the potential dangers of polychlorinated biphenyl (PCB) and methyl mercury excess from …