A glucose-caffeine 'energy drink' ameliorates subjective and performance deficits during prolonged cognitive demand

Appetite. 2004 Jun;42(3):331-3. doi: 10.1016/j.appet.2004.03.001.


Effects of a combination of caffeine and glucose were assessed in two double-blind, placebo-controlled, cross-over studies during extended performance of cognitively demanding tasks. In the first study, 30 participants received two drinks containing carbohydrate and caffeine (68 g/38 mg; 68 g/46 mg, respectively) and a placebo drink, in counter-balanced order, on separate days. In the second study 26 participants received a drink containing 60 g of carbohydrate and 33 mg of caffeine and a placebo drink. In both studies, participants completed a 10-min battery of tasks comprising 2-min versions of Serial 3s and Serial 7s subtraction tasks and a 5-min version of the Rapid Visual Information Processing task (RVIP), plus a rating of 'mental fatigue', once before the drink and six times in succession commencing 10 min after its consumption. In comparison to placebo, all three active drinks improved the accuracy of RVIP performance and both the drink with the higher level of caffeine in first study and the active drink in the second study resulted in lower ratings of mental fatigue. These results indicate that a combination of caffeine and glucose can ameliorate deficits in cognitive performance and subjective fatigue during extended periods of cognitive demand.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Analysis of Variance
  • Beverages*
  • Caffeine / administration & dosage
  • Caffeine / pharmacology*
  • Central Nervous System Stimulants / administration & dosage
  • Central Nervous System Stimulants / pharmacology*
  • Cognition / drug effects*
  • Cross-Over Studies
  • Dose-Response Relationship, Drug
  • Double-Blind Method
  • Glucose / administration & dosage
  • Glucose / pharmacology*
  • Humans
  • Mental Fatigue / drug therapy
  • Mental Fatigue / physiopathology
  • Mental Processes / drug effects
  • Neuropsychological Tests
  • Task Performance and Analysis*
  • Time Factors


  • Central Nervous System Stimulants
  • Caffeine
  • Glucose