A wide range of studies have demonstrated that glucose and/or carbohydrate ingestion can facilitate certain aspects of cognitive performance in healthy young humans (e.g. Kennedy & Scholey, 2000; Sünram-Lea, Foster, Durlach, & Perez, 2002). Recent evidence indicates that different macronutrients may influence cognition and mood in different ways (e.g. Fischer, Colombani, Langhans, & Wenk, 2001; Kaplan, Greenwood, Winocur, & Wolever (2001) R.J. Kaplan, C.E. Greenwood, G. Winocur and T.M.S. Wolever, American Journal of Clinical Nutrition 74 (2001), pp. 687–693. View Record in Scopus | Cited By in Scopus (30)Kaplan, Greenwood, Winocur, & Wolever, 2001). The aim of this study was to examine further the effects of three different macronutrients on mood and cognition. In a within-participant, blind, placebo-controlled design, 18 healthy young adults were administered iso-energetic drinks containing fat, protein or glucose, and a matching inert placebo. Cognitive performance and mood were assessed at baseline, and 15 and 60 min after drink ingestion. Individual differences in dietary restraint were assessed and blood glucose levels were measured. There was general enhancement of memory processes following a protein drink. In addition, psychologically mediated, post-drink improvements in alertness were observed and individual differences in dietary restraint may have moderated cognitive performance following drink administration.