Theanine benefits, dosage, and side effects (2024)

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 is the effect of combining L-theanine with caffeine?

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?

Note that Theanine is also known as:

  • 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

What works and what doesn't?

Unlock the full potential of Examine

Get started

Research Feed

Read all studies
Read all studies
Read all studies

Update History

2023-09-27 00:30:04

Standard FAQ and database update

major

We searched for new studies on theanine, analyzed them, and added their information to our FAQs and database. Additionally, we merged the contents of the research breakdown with the FAQs.

Written By

Thomas Solomon

Edited By

Natalka Roshak

Reviewed By

Nick Milazzo

References

  1. ^Türközü D, Şanlier NL-theanine, unique amino acid of tea, and its metabolism, health effects, and safety.Crit Rev Food Sci Nutr.(2017-May-24)
  2. ^Li MY, Liu HY, Wu DT, Kenaan A, Geng F, Li HB, Gunaratne A, Li H, Gan RYL-Theanine: A Unique Functional Amino Acid in Tea ( L.) With Multiple Health Benefits and Food Applications.Front Nutr.(2022)
  3. ^Chen Z, Wang Z, Yuan H, He NFrom Tea Leaves to Factories: A Review of Research Progress in l-Theanine Biosynthesis and Production.J Agric Food Chem.(2021-Feb-03)
  4. ^Boros K, Jedlinszki N, Csupor DTheanine and Caffeine Content of Infusions Prepared from Commercial Tea Samples.Pharmacogn Mag.(2016)
  5. ^Mu W, Zhang T, Jiang BAn overview of biological production of L-theanine.Biotechnol Adv.(2015)
  6. ^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)
  7. ^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)
  8. ^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)
  9. ^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)
  10. ^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)
  11. ^Yosh*take 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)
  12. ^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)
  13. ^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)
  14. ^Theertham P Rao, Motoko Ozeki, Lekh R JunejaIn Search of a Safe Natural Sleep AidJ Am Coll Nutr.(2015)
  15. ^J F Borzelleca, D Peters, W HallA 13-week dietary toxicity and toxico*kinetic study with l-theanine in ratsFood Chem Toxicol.(2006 Jul)
  16. ^T Terashima, J Takido, H YokogoshiTime-dependent changes of amino acids in the serum, liver, brain and urine of rats administered with theanineBiosci Biotechnol Biochem.(1999 Apr)
  17. ^Manuel Gomez-Ramirez, Beth A Higgins, Jane A Rycroft, Gail N Owen, Jeannette Mahoney, Marina Shpaner, John J FoxeThe deployment of intersensory selective attention: a high-density electrical mapping study of the effects of theanineClin Neuropharmacol.(Jan-Feb 2007)
  18. ^Kakuda T, Nozawa A, Sugimoto A, Niino HInhibition by theanine of binding of 3HAMPA, 3Hkainate, and 3HMDL 105,519 to glutamate receptors.Biosci Biotechnol Biochem.(2002-Dec)
  19. ^Egashira N, Hayakawa K, Osajima M, Mishima K, Iwasaki K, Oishi R, Fujiwara MInvolvement of GABA(A) receptors in the neuroprotective effect of theanine on focal cerebral ischemia in mice.J Pharmacol Sci.(2007-Oct)
  20. ^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)
  21. ^Baba Y, Takihara T, Okamura NTheanine maintains sleep quality in healthy young women by suppressing the increase in caffeine-induced wakefulness after sleep onset.Food Funct.(2023-Jul-31)
  22. ^Gail N Owen, Holly Parnell, Eveline A De Bruin, Jane A RycroftThe combined effects of L-theanine and caffeine on cognitive performance and moodNutr Neurosci.(2008 Aug)
  23. ^Kahathuduwa CN, Wakefield S, West BD, Blume J, Dassanayake TL, Weerasinghe VS, Mastergeorge AEffects of L-theanine-caffeine combination on sustained attention and inhibitory control among children with ADHD: a proof-of-concept neuroimaging RCT.Sci Rep.(2020-Aug-04)
  24. ^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)
  25. ^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)
  26. ^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)

Examine Database References

  1. 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.()
  2. 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)
  3. 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)
  4. 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)
  5. 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)
  6. 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)
  7. 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)
  8. 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)
  9. Executive Function - Yosh*take 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)
  10. 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)
  11. 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)
  12. 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)
  13. Prepulse Inhibition - Miho Ota, Chisato Wakabayashi, Junko Matsuo, Yukiko Kinosh*ta, 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)
  14. Calmness - Song CH, Jung JH, Oh JS, and Kim KSEffects of Theanine on the Release of Brain Alpha Wave in Adult MalesKorean Journal of Medicine.()
  15. 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)
  16. 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.()
  17. Anxiety Symptoms - Kimura K, Ozeki M, Juneja LR, Ohira HL-Theanine reduces psychological and physiological stress responsesBiol Psychol.(2007 Jan)
  18. 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)
  19. 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)
  20. 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)
  21. 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)
  22. 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)
  23. 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)
  24. 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)
  25. 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)
  26. 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)
Theanine benefits, dosage, and side effects (2024)

References

Top Articles
Latest Posts
Article information

Author: Moshe Kshlerin

Last Updated:

Views: 5772

Rating: 4.7 / 5 (57 voted)

Reviews: 88% of readers found this page helpful

Author information

Name: Moshe Kshlerin

Birthday: 1994-01-25

Address: Suite 609 315 Lupita Unions, Ronnieburgh, MI 62697

Phone: +2424755286529

Job: District Education Designer

Hobby: Yoga, Gunsmithing, Singing, 3D printing, Nordic skating, Soapmaking, Juggling

Introduction: My name is Moshe Kshlerin, I am a gleaming, attractive, outstanding, pleasant, delightful, outstanding, famous person who loves writing and wants to share my knowledge and understanding with you.