This question could be investigated by using a population-based randomized controlled trial to assess whether walnut intake shows beneficial effects on teenage brain function (using neuropsychological assessments). It is ethical and feasible to recommend and facilitate walnut intake (30 g/day; Marangoni, 2007; Maranhao, 2011) over a long period of time (e.g. 12 months; de Ruyter, 2012). A Californian walnut contains ~0.40g of n-3 PUFAs (USDA National Nutrient Database for Standard Reference, 2012), such that a few walnuts (kernel 30g) per day would meet recommendations to consume at least 1g of n-3 PUFAs per day (Food and Nutritional Board, Institute of Medicine of the National Academies, US, 2014). Young Spanish adults (16-25 years) eat about 10g of nuts per day on average (Salas, 2013). Sea food also contains high n-3 PUFA concentrations, but sea food interventions are contra-indicated due to their methylmercury content, an important neurotoxic environmental pollutant (Grandjean, 2014). A limitation of using walnuts is that intake is less consistent than with a daily pill supplement of 1g of DHA, although this specific food recommendation is socially cost-effective and would be complied with by a wider range of people in the global health context.