L-Theanine studies datasheet - 2019 Update

Here is a summary list of L-Theanine studies showing its effect on human performance.


Last updated: 14 May 2019 


Human studies  




  • A study of 20 healthy male volunteers stated that a 200mg dose of L-Theanine improves cognitive and neurophysiological measures of selective attention. Theanine and caffeine seem to have additive effects on attention in high doses (Study)

  • The combination of moderate levels of L-Theanine (97mg) and caffeine (40mg) significantly improved accuracy during task switching and self-reported alertness and reduced self-reported tiredness (Study)


Mood / Stress


  • A study of 14 participants concluded that L-Theanine not only reduces anxiety but also attenuates the blood-pressure increase in high-stress-response adults (Study)

  • A study of 20 pharmacy students showed low levels of pre-practice sAA (stress marker) and subjective stress in the theanine-group suggesting that theanine intake suppressed initial stress response of students assigned for a long-term commitment of pharmacy practice (Study

  • In a study of 12 participants L-Theanine intake resulted in a reduction in the heart rate and salivary immunoglobulin A (stress marker) responses to an acute stress task. Thus, it was suggested that the oral intake of L-Theanine could cause anti-stress effects (Study)

  • Another study stated that In human volunteers, α-waves were generated on the occipital and parietal regions of the brain surface within 40 min after the oral administration of theanine (50–200 mg), signifying relaxation without causing drowsiness (Study)

  • Consumption of theanine suppressed the shortened lifespan, cerebral atrophy, learning impairment, behavioural depression and oxidative damage in cerebral DNA caused by psychosocial stress. The intake of theanine might be a potential candidate for suppression of disadvantage under psychosocial stress (Study)




  • In a study of 98 boys with ADHD participants taking L-Theanine (400mg) obtained significantly higher sleep percentage and sleep efficiency scores (Study)



Animal studies 


  •  A study demonstrated that theanine is a safe compound and its repeated oral administration reduces oxidation levels in the rat brain, especially the Cx, by increasing PLC-β1 and -γ1 protein expression, suggesting its favourable effect on the brain in vivo (Study)

  • L-Theanine treatment exhibited a reversal of cognitive impairments and oxidative damage induced by Chronic Restraint Stress (CRS), but also reversed abnormal level of corticosterone in the serum as well as the abnormal levels of catecholamines in the brain and the serum. This study indicated the protective effect of L-Theanine against CRS-induced cognitive impairments in mice (Study)



In Vitro studies 


  • A study investigated protective effects of L-theanine on neurotoxicity induced by Parkinson's Disease-related neurotoxicants, rotenone and dieldrin. The results suggested that L-theanine provides neuroprotection against PD-related neurotoxicants and may be clinically useful for preventing PD symptoms (Study)



L-Theanine food sources 


  • Green tea
  • Black tea
  • Matcha (green tea)



For more information about food sources visit https://ndb.nal.usda.gov/ndb/

For more L-Theanine studies visit https://www.ncbi.nlm.nih.gov/pubmed/?term=l-theanine

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