This review considers the research to date on the role of nutrition in cognitive development in children, with a particular emphasis on the relatively neglected post-infancy period. Undernutrition and deficiencies of iodine, iron, and folate are all important for the development of the brain and the emergent cognitive functions, and there is some evidence to suggest that zinc, vitamin B12, and omega-3 polyunsaturated fatty acids may also be important. Considerations for future research include a focus on the interactions between micronutrients and macronutrients that might be influential in the optimization of cognitive development; investigation of the impact of nutritional factors in children after infancy, with particular emphasis on effects on the developing executive functions; and selection of populations that might benefit from nutritional interventions, for example, children with nutrient deficiencies or those suffering from attention deficit-hyperactivity disorder and dyslexia.

Based on research demonstrating associations between folate, B-12 and B-6 vitamins and cognition and mood, we investigated the effects of short-term supplementation in 211 healthy younger, middle-aged and older women who took either 750 microg of folate, 15 microg of vitamin B-12, 75 mg of vitamin B-6 or a placebo daily for 35 d. In addition, we examined associations between dietary intake of these vitamins and cognition and mood. Usual dietary intake status was estimated using a retrospective, self-report, quantified food frequency questionnaire. Participants completed alternate forms of standardized tests of cognitive processing resources, memory, executive function, verbal ability and self-report mood measures before and after supplementation. Supplementation had a significant positive effect on some measures of memory performance only, and no effect on mood. Dietary intake status was associated with speed of processing, recall and recognition and verbal ability.

Recent research has highlighted the potential impact of nutritional factors and individual micronutrients on the brain and on cognitive performance, especially in older adults. The B vitamins, folate, B12, and B6, are of particular interest because even subclinical deficiencies in these vitamins are thought to be relatively common in the general population and in older adults in particular. Recent cross-sectional and longitudinal studies have provided evidence for an association between these B vitamins and many aspects of cognitive performance and have raised the possibility that even subclinical differences in nutritional status may have a subtle influence on aspects of cognitive performance, especially in older adults and in clinical populations. Preliminary evidence also indicates the effectiveness of supplementation in enhancing cognitive performance in older adults. Important considerations for future research include the use of placebo-controlled intervention studies, sensitive outcome measures of cognitive performance, and exploration of bioavailability and dose-response relationships.