The combination of L-theanine and caffeine improves cognitive performance and increases subjective alertness

Giesbrecht T, et al.

Published in Nutritional Neuroscience

Methodology

Double-blind, placebo-controlled crossover randomised trial; participants completed attention-switching and visual-search tasks plus subjective mood ratings after a single dose of L-theanine 97 mg + caffeine 40 mg or placebo.

Key Findings

In 44 young adults, 97 mg L-theanine plus 40 mg caffeine improved accuracy on a demanding attention-switching task and reduced susceptibility to distracting information versus placebo, and increased self-reported alertness and reduced tiredness; effects on simple reaction time were minimal.

Conclusions

97 mg of L-theanine in combination with 40 mg of caffeine helps to focus attention during a demanding cognitive task.

Limitations

Very small sample of healthy young adults; single acute dose with no chronic-use data; combination design cannot separate theanine from caffeine effects; multiple cognitive endpoints without full multiplicity correction; industry funded.