Randomized trial · 2010

L-theanine and caffeine improve task switching but not intersensory attention or subjective alertness.

SJ Einöther, VE Martens, JA Rycroft, EA De Bruin. Appetite.

Tea ingredients L-theanine and caffeine have repeatedly been shown to deliver unique cognitive benefits when consumed in combination. The current randomized, placebo-controlled, double-blind, cross-over study compared a combination of L-theanine (97 mg) and caffeine (40 mg) to a placebo on two attention tasks and a self-report questionnaire before, and 10 and 60 min after consumption. The combination of L-theanine and caffeine significantly improved attention on a switch task as compared to the placebo, while subjective alertness and intersensory attention were not improved significantly. The results support previous evidence that L-theanine and caffeine in combination can improve attention.

Open source doi:10.1016/j.appet.2010.01.003 PMID 20079786

Edges that cite this paper

Kahathuduwa 2018 found that 200 mg of L-theanine alone sped recognition visual reaction time versus placebo in 20 healthy men. Dassanayake 2023 saw a similar simple-reaction win in 32 young adults and no win on harder attention tasks. Tea-dose theanine alone has often missed.

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What Causes What. “L-theanine and caffeine improve task switching but not intersensory attention or subjective alertness..” https://whatcauseswhat.org/papers/p-pmid-20079786 (atlas updated 2026-09-02).

https://whatcauseswhat.org/papers/p-pmid-20079786