Feeling smart: Effects of caffeine and glucose on cognition, mood and self-judgment

What this study found

Neither caffeine nor glucose improved cognitive performance versus placebo, water, or no treatment. In study 1, caffeine increased subjective activation and feelings of energy, but did not significantly improve self-judgment or any cognitive outcome; glucose produced no significant mood or cognitive benefits. In study 3, caffeine again increased activation, energy, and reduced tiredness, but cognitive performance still did not improve. Overall, the findings do not support universal acute cognitive-enhancing effects of caffeine or glucose, although caffeine can improve subjective mood and…

Study & population

Within-subjects human studies in healthy young adult men with habitual caffeine and sugar use.

Intervention

Across the acute crossover studies, caffeine was administered as coffee containing 200 mg caffeine in study 1 and as caffeinated coffee in study 3; comparators were decaffeinated coffee or no treatment.

Key limitation

Sample sizes were small in the active arms (study 1: N = 17 per active arm; study 3: N = 20 per active arm), limiting power.

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