The series of articles in this supplement addresses some of the particular problems in the assessment of the long-term effects of nutrition on cognition, as well as potential solutions. The articles cover the topics and discussions of a workshop titled “Methodologies to assess long-term effects of nutrition on brain function” that was held on November 12–13, 2009, in Brussels, Belgium, organized by the Nutrition and Mental Performance Task Force of the International Life Sciences Institute (ILSI) Europe. The Task Force aims to promote, guide, and support scientific research on nutritional effects on cognition, with a focus on the methodologies to measure these effects in a reliable, sensitive, and meaningful way. The Task Force's activities include the publication of overviews and general guidelines on cognitive assessment methods in infants, children, adults, and the elderly, with particular reference to nutritional interventions. The specific aim of the current workshop was to contribute to a better understanding of the current methodological limitations and emerging opportunities in the assessment of long-term nutritional effects on brain function and to help guide future methodology development. An introduction to the different articles in the supplement appears in the first article titled “Nutrition and cognition: meeting the challenge to obtain credible and evidence-based facts.”