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L-theanine on Mood and Cognitive Function

L-Theanine is a non-protein amino acid found naturally in green tea. Depending on the type and brewing method of green tea, one cup can contain 5 – 80mg of L-theanine. Most studies investigating the effects of L-theanine utilise a dose of 200mg per day. Promising research suggests the supplementation of L-Theanine to support mental health status.


Following the administration of L-theanine for an extended period (four weeks), studies observed improvements in stress-related symptoms, cognitive function and sleep quality, based on marker scores following the trial.

Cognition function and stress-related symptoms

A mechanism of action of antidepressants involves increased Brain-Derived Neurotrophic Factor (BDNF) levels in the hippocampus. One study observed a similar effect following the administration of L-theanine over four weeks, with increased BDNF expression in the hippocampus via N-methyl-D-aspartate (NMDA) receptors. With antipsychotic-like effects, l-theanine has the potential to reduce stress-related symptoms, including depression and anxiety. Improvements in attention, focus, verbal fluency and executive function scores were all improved with L-theanine administration following the four week trial.

L-theanine and caffeine

Along with L-theanine, caffeine is another natural compound found in green tea. Caffeine inhibits the binding of adenosine, causing the body to feel alert, awake, attentive and have faster reaction times. Despite containing a stimulating dose of caffeine, tea consumption has been observed to present relaxation and calming effects due to the presence of L-theanine. Coffee, on the other hand, does not contain L-theanine, only caffeine which promotes anxiety and jittery symptoms for some individuals. High amounts of caffeine consumption, particularly later in the day, can cause a variety of sleep disturbances including reduced quality and duration of sleep. Research observed the benefits of pairing L-theanine with caffeine to balance out the negative effects of caffeine on its own.

L-theanine and athletic performance

A potential downside to L-theanine utilisation is impaired performance levels immediately following use. The relaxation and sleepiness effect of L-theanine caused athletes to have reduced reaction time when during their training session. This outcome was observed to be reversed when L-theanine supplementation was paired with a dose of caffeine, leading to improved speed and accuracy within performance. L-theanine can be utilised by athletes prior to sleep (after training) to observe relaxation and sleep benefits, without affecting performance.


Have you tired L-theanine?

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  • No

L-theanine is safe to administer, with multiple studies observing minimal adverse effects with supplementation. 


Hidese S, Ogawa S, Ota M, Ishida I, Yasukawa Z, Ozeki M,  Kunugi H. Effects of l-theanine administration on stress-related symptoms and cognitive functions in healthy adults: a randomized controlled trial. Nutrients. 2019;11(10):2362. Available from:


Wakabayashi C, Numakawa T, Ninomiya M, et al. Behavioural and molecular evidence for psychotropic effects in L-theanine. Psychopharmacology. 2012;219:1099–1109. Available from:



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