L-theanine
mg acute
The isolated amino acid from tea, usually 50 to 400 mg as a single oral dose. A cup of tea and a theanine-plus-caffeine mix are different drinks.
Trials give the isolated amino acid and then a reaction-time, attention, or switch task. A cup of tea delivers less theanine along with caffeine and other compounds. Capsules that pair theanine with caffeine are a different drink from theanine alone.
Also called theanine, L-theanine, gamma-glutamylethylamide.
Connected relationships
Randomized trial · Contested
L-theanine→Cognitive performance
Higher L-theanine moves Cognitive performance only in some conditions. Read the mechanism.
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.
Sources
- CN Kahathuduwa et al. (2018). Acute effects of theanine, caffeine and theanine-caffeine combination on attention.
- TL Dassanayake et al. (2023). Dose-response effect of L-theanine on psychomotor speed, sustained attention, and inhibitory control: a double-blind, placebo-controlled, crossover study.
- FL Dodd et al. (2016). A double-blind, placebo-controlled study evaluating the effects of caffeine and L-theanine both alone and in combination on cerebral blood flow, cognition and mood.
- CF Haskell et al. (2008). The effects of L-theanine, caffeine and their combination on cognition and mood.
- T Giesbrecht et al. (2011). The combination of L-theanine and caffeine improves cognitive performance and increases subjective alertness.
- SJ Einöther et al. (2010). L-theanine and caffeine improve task switching but not intersensory attention or subjective alertness.