Ward-Ritacco, C. L., Wilson, A. R., & O’Connor, P. J. (2021). An apple extract beverage combined with caffeine can improve alertness, mental fatigue, and information processing speed. Journal of Cognitive Enhancement, 5, 267–279. doi:10.1007/s41465-020-00204-1

Abstract:

The psychological effects of low-dose caffeine combined with polyphenols from apples have rarely been explored scientifically yet synergistic effects are plausible. A randomized, double-blind, placebo-controlled cross-over experiment was used to test the psychological effects of apple extract beverages combined with 10, 20, 37.5, and 75 mg caffeine. Comparisons were made to both a placebo drink that was artificially sweetened and colored to mimic the test beverages and a positive control drink with 75 mg caffeine but without apple extract. Compared to placebo, it was hypothesized that dose-dependent improvements in cognitive performance, mood, and motivation would be realized after consuming the beverage with apple extract containing added caffeine. Outcomes were assessed before, 60 to 110, and 125 to 175 min post-beverage. The positive control beverage resulted in more serial seven subtractions, greater motivation to perform cognitive tasks, and reduced feelings of fatigue (all p < .005). The study found that psychological effects (i) were not observed for beverages containing apple extract and 10 or 20 mg caffeine, (ii) of the apple extract beverage containing 75 mg caffeine generally mimicked the effects of the positive control drink and significantly increased serial seven processing speed, and (iii) of the apple extract beverage containing 37.5 mg improved feelings of alertness and mental fatigue. In sum, effects of apple extract combined with caffeine were not dose-dependent; the apple extract beverage containing 75 mg caffeine improved information processing speed and the apple extract beverage with 37.5 mg caffeine improved feelings of alertness and mental fatigue.