Cognitive and physiological effects of an "energy drink": an evaluation of the whole drink and of glucose, caffeine and herbal flavouring fractions.
BACKGROUND
Both glucose and caffeine can improve aspects of cognitive performance and, in the case of caffeine, mood. There are few studies investigating the effects of the two substances in combination.


OBJECTIVE
We assessed the mood, cognitive and physiological effects of a soft drink containing caffeine and glucose as well as flavouring levels of herbal extracts. The effects of different drink fractions were also evaluated.


METHODS
Using a randomised, double-blind, balanced, five-way crossover design, 20 participants who were overnight fasted and caffeine-deprived received 250 ml drinks containing 37.5 g glucose; 75 mg caffeine; ginseng and ginkgo biloba at flavouring levels; a whole drink (containing all these substances) or a placebo (vehicle). Participants were assessed in each drink condition, separated by a 7-day wash-out period. Cognitive, psychomotor and mood assessment took place immediately prior to the drink then 30 min thereafter. The primary outcome measures included five aspects of cognitive performance from the Cognitive Drug Research assessment battery. Mood, heart rate and blood glucose levels were also monitored.


RESULTS
Compared with placebo, the whole drink resulted in significantly improved performance on "secondary memory" and "speed of attention" factors. There were no other cognitive or mood effects.


CONCLUSIONS
This pattern of results would not be predicted from the effects of glucose and caffeine in isolation, either as seen here or from the literature addressing the effects of the substances in isolation. These data suggest that there is some degree of synergy between the cognition-modulating effects of glucose and caffeine which merits further investigation.
Scholey
Andrew B
AB
Human Cognitive Neuroscience Unit, Division of Psychology, Northumbria University, Newcastle upon Tyne, NE1 8ST, UK. a.scholey@unn.ac.uk
Kennedy
David O
DO
D000293:Adolescent; D000328:Adult; D000339:Affect / Q000187:drug effects; D001143:Arousal / Q000187:drug effects; D001628:Beverages; D001786:Blood Glucose / Q000378:metabolism; D002110:Caffeine / Q000494:pharmacology*; D000697:Central Nervous System Stimulants / Q000494:pharmacology*; D003071:Cognition / Q000187:drug effects*; D005260:Female; D005421:Flavoring Agents / Q000494:pharmacology*; D005947:Glucose / Q000494:pharmacology*; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D008570:Memory, Short-Term / Q000187:drug effects; D011939:Mental Recall / Q000187:drug effects; D009483:Neuropsychological Tests; D010775:Photic Stimulation; D010944:Plants / Q000737:chemistry; D011597:Psychomotor Performance / Q000187:drug effects; D011930:Reaction Time / Q000187:drug effects
D001786:Blood Glucose; D000697:Central Nervous System Stimulants; D005421:Flavoring Agents; D002110:Caffeine; D005947:Glucose