Impact of Various Caffeine Vehicles on Mood and Cognitive, Neurological and Physiological Functions over Five Hours

Abstract

Although college students’ caffeine consumption has increased over the last decade, studies have not yet determined the time frame in which caffeine exerts its effects nor the impact of the vehicle by which caffeine is consumed. Sixty college students were randomly divided into one placebo (flour) and three caffeine treatment groups: 5-Hour Energy ®, Starbucks DoubleShot ®, or caffeine powder; all dosed at 3 mg caffeine/kg of body weight. A battery of tests was performed prior to dosing and repeated 2.5 and 5 hours post treatment. Mood was self-reported on a scale of 1-100 for happiness, alertness and focus. Cognitive function was assessed by Stroop and memory tests. Reaction time, heart rate, blood glucose, and electroencephalogram were recorded. All initial measurements across groups and group baselines vs 2.5 and 5 hour results were analyzed by ANOVA followed, when indicated, by post hoc t-tests at 95% confidence levels and only significant results are reported. All caffeine groups had elevations in mood and faster reaction times at 2.5 hours (most effects sustained for 5 hours). The 5-Hour Energy® group rated alertness higher than other caffeine treatments, and was the only group to demonstrate decreases in alpha waves, memory improvements, and impaired glucose homeostasis. All caffeine groups had improved cognition with decreased Stroop test time and the caffeine powder and 5-Hour Energy ® groups had improved Stroop test accuracy at 2.5 hours. The 5-Hour Energy shot ® had the greatest proportion of sustained caffeine effects across test parameters.