The aim of this study was to investigate the effects of guarana supplementation on cognitive performance before and after a bout of maximal intensity cycling and to compare this to an equivalent caffeine dose. Twenty-five participants completed the randomised double-blind crossover trial by performing cognitive tests with one of three supplements, on three different days: guarana (125 mg/kg), caffeine (5 mg/kg) or placebo (65 mg/kg protein powder). After 30 min of rest, participants performed simple (SRT) and choice reaction time (CRT) tests, an immediate word recall test and Bond–Lader mood scale. This was followed by a cycling V̇O2max test, and cognitive tests were then immediately repeated. Guarana supplementation decreased CRT before exercise (407 (sd 45) ms) in comparison with placebo (421 (sd 46) ms, P = 0·030) but not caffeine (417 (sd 42) ms). SRT after exercise decreased following guarana supplementation (306 (sd 28) ms) in comparison with placebo (323 (sd 32) ms, P = 0·003) but not caffeine (315 (sd 32) ms). Intra-individual variability on CRT significantly improved from before (111·4 (sd 60·5) ms) to after exercise (81·85 (sd 43·1) ms) following guarana supplementation, and no differences were observed for caffeine and placebo (P > 0·05). Alertness scores significantly improved following guarana supplementation (63·3 (sd 13·8)) in comparison with placebo (57·4 (sd 13·4), P = 0·014) but not caffeine (61·2 (sd 12·8)). There were no changes to V̇O2max, immediate word recall or any other Bond–Lader mood scales. Guarana supplementation appears to impact several parameters of cognition. These results support the use of guarana supplementation to possibly maintain speed of attention immediately following a maximal intensity exercise test (V̇O2max).

Associations between dietary factors and general cognition in the elderly have been documented; however, little is known about reaction time ability in relation to midlife diet. The present study aimed to investigate associations between reaction time and midlife dietary factors, specifically foods, nutrients and Mediterranean diet (MeDi) pattern. The UK Women’s Cohort Study collected dietary information from middle-aged women (52 (sd 9·4) years old) using a validated 217-item FFQ in 1995–1998. In 2010–2011, a sub-group of 664 participants completed online reaction time ability tests including simple reaction time (SRT) and choice reaction time; 503 participants were eligible for analysis. Participants were grouped into fast and slow groups by their median reaction time. The intake of particular foods, nutrients, adherence to the MeDi and cooking methods (roasting/baking, frying and barbecuing/grilling) were explored in relation to reaction times. We did not find any significant associations between reaction times and investigated foods, nutrients or adherence to the MeDi in adjusted models. However, consumers of roasted/baked fish and fried vegetables were associated with slower SRT (adjusted OR 1·46, 95 % CI 1·00, 2·13, P = 0·049; and adjusted OR 1·64, 95 % CI 1·12, 2·39, P = 0·010, respectively) compared with non-consumers of that particularly cooked food. Overall, our findings show no significant associations between midlife diet and reaction time ability 10–15 years later.