summary
background Energy drinks have become more and more popular since the late nineties. The manufactures claim that these drinks improve physical endurance, reaction speed and concentration. The main ingredients of energy drinks are caffeine, sugar, taurine and glucuronolactone. According to the manufacturers, the stimulating effects of these drinks are due to interaction between the various ingredients.
aim To investigate whether energy drinks do indeed improve cognitive performance and to find out which ingredients are responsible for this effect and other benefits.
method We searched the literature for the period from 1997 to 2006 on the basis of Medline, by using the search term 'energy drink or energy drinks' and restricting the search to 'humans'.
results Not only did focused and sustained attention improve significantly but so did reaction speed in all sorts of reaction-time tasks. Memory improved too, but not to the same degree.
conclusion The findings suggest that most of the effects of energy drinks on cognitive performance are related mainly to the presence of caffeine. Further investigation is needed into the effects of the lesser known ingredients of energy drinks (taurine, glucuronolactone) if we are to obtain a better understanding of the possible interactions.