Later these children often perform better at school. This may be related to the fact that breast milk contains the types of fat needed for the development of the brain and retina. Docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA) and arachidonic acid (AA) are long chain polyunsaturated fatty acids found in breast milk and fish oils. DHA and AA have been added to some infant formulas, however in these studies it is difficult to separate the fact that those children who were breast-fed as babies were more likely to come from higher socio-economic groups that may reflect higher parental education, better nutrition and housing and perhaps a more positive attitude to education.
There appears to be a link between DHA and EPA and behavioural problems in children. Several studies have looked at the effects of DHA and EPA supplements for children with learning difficulties, especially those children with autism, attention-deficit hyperactivity disorder, dyslexia or dyspraxia. The results have been mixed, but a recent trial involving 120 children aged six to 11 years with various types of learning difficulties found that in some their reading age and attention improved dramatically.
Over the six-month trial the children took a daily dose of 500mg of EPA. A complete analysis of this data is yet to be published and it is important to realise that not all children with learning difficulties appear to benefit from fish oil supplements. This is because there are many causes of learning difficulties, not just a deficiency of DHA and EPA.
What is clearly missing in the fish oil story so far is the link between normal children, academic achievement and fish oils. In short, there is no evidence that fish oils enhances exam success. And other nutrients, such as iron and zinc, have a potential role in cognitive function. However, there's no single nutrient responsible for mental performance and it's probably the interaction of many that influence it. This reinforces the idea of a varied diet, for children and adults, including a serving of oily fish once a week.
If you really want to give children a concentration boost, the evidence is arguably stronger for a large helping of unrefined carbohydrates at breakfast, such as Weetabix.
Dr Toni Steer is a nutritionist at the Medical Research Council's Human Nutrition Research unit, Cambridge