What is L-theanine?
L-theanine is a naturally occurring amino acid, although it isn’t used as a building block for protein synthesis,[1][2] unlike the 20 standard protein-forming amino acids that are synthesized by the genetic code. Several types of tea, including black, oolong, and green tea, contain theanine (generally <50 mg per serving).[3][2][4] When higher doses are desired, theanine can also be taken as a dietary supplement; the theanine in supplements may be extracted from tea[3] or chemically synthesized using bacterial enzymes.[5]
What are L-theanine’s main benefits?
The current evidence shows that supplementation with L-theanine may help reduce stress and anxiety in people experiencing acutely stressful situations.[6] Furthermore, L-theanine may also prevent the increase in blood pressure caused by stressful mental tasks.[7] Some small studies have also found that L-theanine might lower depression and anxiety scores in healthy people and in people with major depressive disorder.[8][9]
Supplementation with L-theanine may also improve some aspects of cognitive function, including attention, executive function, and memory.[10][11][8][9] That said, L-theanine has been found to impair executive function and lower attentional control when people are in an emotionally aroused state[12] or are undertaking stressful mental tasks.[13]
Further evidence suggests that supplementation with L-theanine might also enhance sleep quality[8][9] by promoting a more relaxed state in the brain.[14] However, it is important to note that this evidence is derived predominantly from studies of healthy people. There is currently insufficient evidence to make firm conclusions about whether theanine can improve stress, anxiety, depression, cognitive function, or sleep quality in people with chronic conditions.
What are L-theanine’s main drawbacks?
The main drawback is that the specific effects of L-theanine have only been tested in a small number of randomized controlled trials which predominantly included healthy people without chronic conditions. Therefore, further high-quality studies are needed to bolster the current evidence.
The clinical evidence cited above shows that supplementation with L-theanine is well-tolerated, with no known reports of adverse effects or toxicity. In rodents, L-theanine has remarkably low toxicity, with one study failing to find any toxic effects when administering up to 4,000 mg of L-theanine per kg of body weight daily for 13 weeks.[15] Additional animal studies have reported similar results with no observed toxicity at remarkably high doses.[1] Consequently, it is generally assumed that L-theanine is safe for humans to consume,[1] particularly given its long history of consumption in tea. However, specific safety studies in humans are lacking.
How does L-theanine work?
After consumption, L-theanine can cross the blood-brain barrier[16] and affect brain activity by promoting increased alpha-wave activity,[17][1][2] a pattern of brain activity associated with a more relaxed state. This may explain its stress-reducing and anxiety-reducing effects.[8]
In animal studies, L-theanine has been shown to affect neurotransmitter signaling in the brain by behaving like a glutamate reuptake inhibitor as well as a glutamate receptor antagonist.[18] Other animal studies demonstrate that L-theanine can also exert neuroprotective effects via its action on gamma-aminobutyric-acid-A (GABA-A) receptors.[19] However, further investigation in humans is needed to confirm these mechanisms of action.[1][2]
What are other names for Theanine
- L-Theanine
- 5-N-Ethyl-Glutamine
- γ-glutamylethylamide
Dosage information
Clinical studies typically use L-theanine at a dosage of 100–400 milligrams (mg) per day.
Examine Database: Theanine
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Frequently asked questions
L-theanine is a naturally occurring amino acid, although it isn’t used as a building block for protein synthesis,[1][2] unlike the 20 standard protein-forming amino acids that are synthesized by the genetic code. Several types of tea, including black, oolong, and green tea, contain theanine (generally <50 mg per serving).[3][2][4] When higher doses are desired, theanine can also be taken as a dietary supplement; the theanine in supplements may be extracted from tea[3] or chemically synthesized using bacterial enzymes.[5]
The current evidence shows that supplementation with L-theanine may help reduce stress and anxiety in people experiencing acutely stressful situations.[6] Furthermore, L-theanine may also prevent the increase in blood pressure caused by stressful mental tasks.[7] Some small studies have also found that L-theanine might lower depression and anxiety scores in healthy people and in people with major depressive disorder.[8][9]
Supplementation with L-theanine may also improve some aspects of cognitive function, including attention, executive function, and memory.[10][11][8][9] That said, L-theanine has been found to impair executive function and lower attentional control when people are in an emotionally aroused state[12] or are undertaking stressful mental tasks.[13]
Further evidence suggests that supplementation with L-theanine might also enhance sleep quality[8][9] by promoting a more relaxed state in the brain.[14] However, it is important to note that this evidence is derived predominantly from studies of healthy people. There is currently insufficient evidence to make firm conclusions about whether theanine can improve stress, anxiety, depression, cognitive function, or sleep quality in people with chronic conditions.
As described above, theanine generally has calming or relaxing effects.[6][7][8][9] On the other hand, caffeine is a powerful central nervous system stimulant that is added to some energy drinks and naturally found in tea, coffee, and chocolate. Because tea contains both L-theanine and caffeine, some clinical studies have investigated the effects of theanine and caffeine individually and in combination. The current evidence shows that theanine might diminish some of the less desirable physiological effects of caffeine. For example, L-theanine has been shown to blunt both caffeine’s blood-pressure-increasing effects[20] and its sleep-disrupting effects.[21] However, theanine does not appear to blunt the beneficial effects of caffeine on cognitive performance. Instead, the above-described beneficial effects of theanine on some aspects of cognitive function,[10][11][8][9] such as attention, have been found to be enhanced when caffeine is simultaneously ingested.[22][23][24][25][13] That said, not all studies have found this synergistic effect.[26][20] Overall, dose-response studies of L-theanine and caffeine are currently lacking, and the existing studies are small; larger randomized controlled trials are needed to clarify the interaction between theanine and caffeine. Furthermore, the influence of theanine on the exercise-related performance-enhancing effect of caffeine is currently unclear.
The main drawback is that the specific effects of L-theanine have only been tested in a small number of randomized controlled trials which predominantly included healthy people without chronic conditions. Therefore, further high-quality studies are needed to bolster the current evidence.
The clinical evidence cited above shows that supplementation with L-theanine is well-tolerated, with no known reports of adverse effects or toxicity. In rodents, L-theanine has remarkably low toxicity, with one study failing to find any toxic effects when administering up to 4,000 mg of L-theanine per kg of body weight daily for 13 weeks.[15] Additional animal studies have reported similar results with no observed toxicity at remarkably high doses.[1] Consequently, it is generally assumed that L-theanine is safe for humans to consume,[1] particularly given its long history of consumption in tea. However, specific safety studies in humans are lacking.
After consumption, L-theanine can cross the blood-brain barrier[16] and affect brain activity by promoting increased alpha-wave activity,[17][1][2] a pattern of brain activity associated with a more relaxed state. This may explain its stress-reducing and anxiety-reducing effects.[8]
In animal studies, L-theanine has been shown to affect neurotransmitter signaling in the brain by behaving like a glutamate reuptake inhibitor as well as a glutamate receptor antagonist.[18] Other animal studies demonstrate that L-theanine can also exert neuroprotective effects via its action on gamma-aminobutyric-acid-A (GABA-A) receptors.[19] However, further investigation in humans is needed to confirm these mechanisms of action.[1][2]
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References
Examine Database References
- Reaction Time - Akiko Higashiyama, Hla Hla Htay, Makoto Ozeki, Lekh R. Juneja, Mahendra P. KapoorEffects of l-theanine on attention and reaction time responseJournal of Functional Foods.()
- Reaction Time - Chanaka N Kahathuduwa, Tharaka L Dassanayake, A M Tissa Amarakoon, Vajira S WeerasingheAcute effects of theanine, caffeine and theanine-caffeine combination on attentionNutr Neurosci.(2017 Jul)
- Reaction Time - Crystal F Haskell, David O Kennedy, Anthea L Milne, Keith A Wesnes, Andrew B ScholeyThe effects of L-theanine, caffeine and their combination on cognition and moodBiol Psychol.(2008 Feb)
- Reaction Time - Chanaka N Kahathuduwa, Chathurika S Dhanasekara, Shao-Hua Chin, Tyler Davis, Vajira S Weerasinghe, Tharaka L Dassanayake, Martin Binksl-Theanine and caffeine improve target-specific attention to visual stimuli by decreasing mind wandering: a human functional magnetic resonance imaging studyNutr Res.(2018 Jan)
- Reaction Time - John J Foxe, Kristen P Morie, Peter J Laud, Matthew J Rowson, Eveline A de Bruin, Simon P KellyAssessing the effects of caffeine and theanine on the maintenance of vigilance during a sustained attention taskNeuropharmacology.(2012 Jun)
- Reaction Time - Peter J Rogers, Jessica E Smith, Susan V Heatherley, C W Pleydell-PearceTime for tea: mood, blood pressure and cognitive performance effects of caffeine and theanine administered alone and togetherPsychopharmacology (Berl).(2008 Jan)
- Executive Function - Shinsuke Hidese, Shintaro Ogawa, Miho Ota, Ikki Ishida, Zenta Yasukawa, Makoto Ozeki, Hiroshi KunugiEffects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled TrialNutrients.(2019 Oct 3)
- Executive Function - Grace E Giles, Caroline R Mahoney, Tad T Brunyé, Holly A Taylor, Robin B KanarekCaffeine and theanine exert opposite effects on attention under emotional arousalCan J Physiol Pharmacol.(2017 Jan)
- Executive Function - Yoshitake Baba, Shun Inagaki, Sae Nakagawa, Toshiyuki Kaneko, Makoto Kobayashi, Takanobu TakiharaEffects of l-Theanine on Cognitive Function in Middle-Aged and Older Subjects: A Randomized Placebo-Controlled StudyJ Med Food.(2021 Apr)
- Attention - Simon P Kelly, Manuel Gomez-Ramirez, Jennifer L Montesi, John J FoxeL-theanine and caffeine in combination affect human cognition as evidenced by oscillatory alpha-band activity and attention task performanceJ Nutr.(2008 Aug)
- Attention - F L Dodd, D O Kennedy, L M Riby, C F Haskell-RamsayA double-blind, placebo-controlled study evaluating the effects of caffeine and L-theanine both alone and in combination on cerebral blood flow, cognition and moodPsychopharmacology (Berl).(2015 Jul)
- Attention - Dassanayake TL, Kahathuduwa CN, Weerasinghe VSL-theanine improves neurophysiological measures of attention in a dose-dependent manner: a double-blind, placebo-controlled, crossover study.Nutr Neurosci.(2022-Apr)
- Prepulse Inhibition - Miho Ota, Chisato Wakabayashi, Junko Matsuo, Yukiko Kinoshita, Hiroaki Hori, Kotaro Hattori, Daimei Sasayama, Toshiya Teraishi, Satoko Obu, Hayato Ozawa, Hiroshi KunugiEffect of L-theanine on sensorimotor gating in healthy human subjectsPsychiatry Clin Neurosci.(2014 May)
- Attention - Shinsuke Hidese, Miho Ota, Chisato Wakabayashi, Takamasa Noda, Hayato Ozawa, Tsutomu Okubo, Hiroshi KunugiEffects of chronic l-theanine administration in patients with major depressive disorder: an open-label studyActa Neuropsychiatr.(2017 Apr)
- Anxiety Symptoms - Kristy Lu, Marcus A. Gray, Chris Oliver, David T. Liley, Ben J. Harrison, Cali F. Bartholomeusz, K. Luan Phan and Pradeep J. NathanThe acute effects of L-theanine in comparison with alprazolam on anticipatory anxiety in humansHuman Psychopharmacology.()
- Anxiety Symptoms - Kimura K, Ozeki M, Juneja LR, Ohira HL-Theanine reduces psychological and physiological stress responsesBiol Psychol.(2007 Jan)
- Anxiety Symptoms - Williams JL, Everett JM, D'Cunha NM, Sergi D, Georgousopoulou EN, Keegan RJ, McKune AJ, Mellor DD, Anstice N, Naumovski NThe Effects of Green Tea Amino Acid L-Theanine Consumption on the Ability to Manage Stress and Anxiety Levels: a Systematic Review.Plant Foods Hum Nutr.(2020-Mar)
- Stress Signs and Symptoms - Moulin M, Crowley DC, Xiong L, Guthrie N, Lewis EDSafety and Efficacy of AlphaWave(®) L-Theanine Supplementation for 28 Days in Healthy Adults with Moderate Stress: A Randomized, Double-Blind, Placebo-Controlled Trial.Neurol Ther.(2024 Aug)
- Sleep Quality - Lyon MR, Kapoor MP, Juneja LRThe effects of L-theanine (Suntheanine®) on objective sleep quality in boys with attention deficit hyperactivity disorder (ADHD): a randomized, double-blind, placebo-controlled clinical trialAltern Med Rev.(2011 Dec)
- Sleep Quality - .(2024-06-16)
- Anxiety Symptoms - Ai Yoto, Mao Motoki, Sato Murao, Hidehiko YokogoshiEffects of L-theanine or caffeine intake on changes in blood pressure under physical and psychological stressesJ Physiol Anthropol.(2012 Oct 29)
- Anxiety Symptoms - Sarris J, Byrne GJ, Cribb L, Oliver G, Murphy J, Macdonald P, Nazareth S, Karamacoska D, Galea S, Short A, Ee C, Birling Y, Menon R, Ng CHL-theanine in the adjunctive treatment of generalized anxiety disorder: A double-blind, randomised, placebo-controlled trialJ Psychiatr Res.(2019 Mar)
- Salivary Alpha-Amylase - Keiko Unno, Naoki Tanida, Naoto Ishii, Hiroyuki Yamamoto, Kazuaki Iguchi, Minoru Hoshino, Atsushi Takeda, Hayato Ozawa, Tsutomu Ohkubo, Lekh Raj Juneja, Hiroshi YamadaAnti-stress effect of theanine on students during pharmacy practice: positive correlation among salivary α-amylase activity, trait anxiety and subjective stressPharmacol Biochem Behav.(2013 Oct)
- Interleukin 4 - A Juszkiewicz, A Glapa, P Basta, E Petriczko, K Żołnowski, B Machaliński, J Trzeciak, K Łuczkowska, A Skarpańska-StejnbornThe effect of L-theanine supplementation on the immune system of athletes exposed to strenuous physical exerciseJ Int Soc Sports Nutr.(2019 Feb 15)
- Heart Rate - Jackson Williams, Andrew J McKune, Ekavi N Georgousopoulou, Jane Kellett, Nathan M D'Cunha, Domenico Sergi, Duane Mellor, Nenad NaumovskiThe Effect of L-Theanine Incorporated in a Functional Food Product (Mango Sorbet) on Physiological Responses in Healthy Males: A Pilot Randomised Controlled TrialFoods.(2020 Mar 23)
- Cortisol - Chanoch Miodownik, Rachel Maayan, Yael Ratner, Vladimir Lerner, Leonid Pintov, Maria Mar, Abraham Weizman, Michael S RitsnerSerum levels of brain-derived neurotrophic factor and cortisol to sulfate of dehydroepiandrosterone molar ratio associated with clinical response to L-theanine as augmentation of antipsychotic therapy in schizophrenia and schizoaffective disorder patientsClin Neuropharmacol.(Jul-Aug 2011)
- Subjective Well-Being - Ritsner MS, Miodownik C, Ratner Y, Shleifer T, Mar M, Pintov L, Lerner VL-theanine relieves positive, activation, and anxiety symptoms in patients with schizophrenia and schizoaffective disorder: an 8-week, randomized, double-blind, placebo-controlled, 2-center studyJ Clin Psychiatry.(2011 Jan)