Main effects of energy drinks on mood, reaction time and brain regions

Abstract

Effects of energy drinks (ED) are attributed to the combination of their three main ingredients: caffeine, taurine, and glucose. The primary objective of this study was to evaluate the main effects and interactions of these ingredients on mood, reaction time during a working memory task and to identify the specific brain regions involved using functional Magnetic Resonance Images (fMRI). In a double-blind, mixed factor and repeated measurement design, 12 healthy volunteers (6 male, 6 females) received one of four treatments (200 mg caffeine/0 mg taurine, 0 mg caffeine/2000 mg taurine, 200 mg caffeine/2000 mg taurine, 0 mg caffeine/0 mg taurine) on each of four separated days. Between-participants treatment was a glucose (11 g of glucose) or placebo (3 g of Stevia). All participants were evaluated with a mood questionnaire in three times and underwent a working memory task, where reaction time was registered, while fMRI were acquired. Functional images were analyzed considering treatment and task difficulty as within-participants in a repeated measurements general linear model. Our results shown that glucose had the most consistent effects on mood, decreasing feelings of tension, depression, anger and fatigue and increasing feeling of vigor. However, reaction time had significant differences only for task difficulty without interactions due to the treatment or glucose intake. Significant activations of brain regions were located at frontal, temporal and cingulate gyrus but main effects and interactions with treatment and glucose were explained only for the task difficulty.