A randomized, placebo-controlled crossover trial of a decaffeinated energy drink shows no significant acute effect on mental energy

Abstract

Background: "Energy drinks" are heavily marketed to the general public, across the age spectrum. The efficacy of decaffeinated energy drinks in enhancing subjective feelings of energy (s-energy) is controversial. Objective: The authors sought to test the efficacy of the caffeine-free version of a popular energy drink compared with a placebo drink. Methods: This study was a randomized, double-blind, placebo-controlled, crossover trial in 223 healthy men and women aged 18-70 y with intention-to-treat and completers analysis. Participants were randomly assigned to consumption of either the decaffeinated energy drink or a placebo drink on testing day 1, and the other drink a week later. A battery of computer-based mood and cognitive tests to assess s-energy was conducted at baseline and at 0.5, 2.5, and 5 h post-ingestion. The main outcome measures were 1) mood, which was assessed by using a General Status Check Scale and the Profile of Mood States 2nd edition brief form, and 2) cognitive measures, including the N-back task (reaction time and accuracy), Reaction Time test, Flanker task (distraction avoidance), and Rapid Visual Information Processing test. Results: No statistically significant or meaningful benefits were observed for any outcome measure, including mood and cognitive measures. Analyses of mean differences, slopes, and median differences were consistent. Conclusions: No differences were detected across a range of mood/cognitive/behavioral/s-energy-level tests after consumption of the energy drink compared with a placebo drink in this diverse sample of adults. Thus, we found strong evidence that the energy drink is not efficacious in enhancing s-energy levels, nor any related cognitive or behavioral variables measured. In light of federal regulations, these findings suggest that labeling and marketing of some products which claim to provide these benefits may be unsubstantiated. This trial was registered at www.clinicaltrials.gov as NCT02727920.