Participants were non-smokers and regular caffeine consumers (at least one caffeinated beverage per day).
Caffeine, not taurine or glucose, is likely responsible for reported changes in cognitive performance following consumption of energy drinks, especially in caffeine-withdrawn habitual caffeine consumers.
We evaluated the effects of caffeine, taurine, and glucose alone and in combination on cognitive performance and mood in 24-hour caffeine-abstained habitual caffeine consumers.
20 healthy, male, habitual caffeine consumers aged 40 61 years were administered 100 mg of caffeine in a double-blind placebo-controlled crossover design.
The subjects, all moderate caffeine consumers, underwent two scanning sessions on a 1.5-T MR-Scanner separated by a 24- to 48-h interval.
On the verbal test, nappers were best by a wide margin, and the caffeine consumers did no better than those given a placebo.
Following an overnight fast, low caffeine consumers (N = 36; M = 42.5 mg/day caffeine) completed 5 counterbalanced test sessions (normal consumption, 0 mg, 100 mg, 200 mg, and 400 mg) separated by at least 3 days.
Writing in the journal Nature Neuroscience, Yassa described how 44 volunteers who were not heavy caffeine consumers and had abstained for at least a day were shown a rapid sequence of pictures on a computer screen.
And the FDA has taken aim at the most potent form of caffeine consumers can purchase: bulk bags of the chemical that can cost as little as $10 per pound.
Using a randomized, double-blind, mixed design, 48 habitual caffeine consumers (18 male, 30 female) who were 24-hour caffeine deprived 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 separate days, separated by a 3-day wash-out period.
