Over the last two decades there have been many claims that what children eat has a major impact upon their performance at school, with many studies claiming that breakfast, in particular, is a strong contributor to concentration and learning during the school day. There is also a well-recognised phenomenon called the ‘post-prandial dip’, which is a drop off in physical and cognitive performance following a lunchtime meal. This is easily seen when granddad falls asleep in his armchair after Sunday lunch, but occurs in both adults and children of all ages. The post-lunch dip is a real phenomenon that has more to do with time of day and circadian rhythms than consuming food (it even happens in people who have not eaten lunch and don’t know what time of day it is) but it is certainly made worse by a high-carbohydrate lunch.

Burrows and colleagues have published a systematic review in the Journal of Human Nutrition and Dietetics (http://onlinelibrary.wiley.com/wol1/doi/10.1111/jhn.12407/abstract) which addressed the question of whether there is an association between dietary intake and academic performance in school children. The review found 40 mostly cross-sectional studies of children over the age of 10 ,which included measures of dietary intake and a measure of academic performance.  The review found that there was some evidence of a modest link between breakfast performance and achievement, with children who consume breakfast, as opposed to fasting in the morning. There was also some evidence that children with high junk food consumption had worse academic performance. These findings are consistent with other reviews in this area and it is suggested that the benefits of improving dietary quality are greatest where children are underweight and presumably undernourished.

One of the problems with the literature in this area that was highlighted by the authors was a lack of high quality methodology. Measuring academic performance is often very subjective and can be influenced strongly by observer bias. Academic performance is also a complex outcome which is a product of children’s cognitive abilities, motivation, behaviour and parental influences. It is well known that children’s diets are also strongly influenced by parental lifestyles and socioeconomic status and these factors may be confounding, particularly where looking at associations of breakfast or junk food consumption in relation to performance. Dietary quality and educational achievement are both disadvantaged by poverty, so any association may not be causal.