Understanding the role of nutrition in the brain and behavioral development of toddlers and preschool children: identifying and addressing methodological barriers.

The preschool years (i.e. 1-5 years of age) is a time of rapid and dramatic postnatal brain development (i.e. neural plasticity), and of fundamental acquisition of cognitive development (i.e. working memory, attention and inhibitory control). Also, it is a time of transition from a direct maternal mediation/selection of diet-based nutrition to food selection that is more based on self-selection and self-gratification. However, there have been fewer published studies in preschool children than in infants or school-aged children that examined the role of nutrition in brain/mental development (125 studies versus 232 and 303 studies, respectively during the last 28 years). This may arise because of age-related variability, in terms of individual differences in temperament, linguistic ability, and patterns of neural activity that may affect assessment of neural and cognitive development in pre-school children. In this review, we suggest several approaches for assessing brain function in children that can be refined. It would be desirable if the discipline developed some common elements to be included in future studies of diet and brain function, with the idea that they would complement more targeted measures based on time of exposure and understanding of data from animal models. Underlining this approach is the concept of 'window of sensitivity' during which nutrients may affect postnatal neural development: investigators and expert panels need to look specifically for region-specific changes and do so with understanding of the likely time window during which the nutrient was, or was not available.