L Theanine


Updated 6/9/19

Many of our patient programs here at Sanctuary include L-theanine, and it has a long and honorable record in clinical care at our office.  For patients needing something to relax, whether in order to help with sleep or just to settle anxiety, this non-essential amino acid works through GABA and alpha waves to both relax mood and improve cognitive function.  Even though our bodies do not use this amino acid to manufacture any proteins, this green tea derived chemical still benefits our patients in many ways.

Sleep:  While not acting as a true sedative, the relaxed state of mind encouraged by this chemical allows many patients to fall into a restorative sleep. 

Anxiety: By helping one to relax while avoiding excessive sedation, theanine works for many patients who need daytime anti-anxiety supplements. 

Cognitive Enhancement:  By promoting alpha brain waves and relaxation, studies indicate that it can improve cognitive function.  One study showed improvements for individuals with mild cognitive impairment.

Schizophrenia:  In one study, some symptoms of schizophrenia and schizo-affective disorder were improved.

Neuroinflammation: Theanine lowered experimental inflammation in one study possibly through ERK/p38 and/or NF-kB

STRESS:  In rats, theanine protected from stress induced memory loss.  They also appear to have lower corticosterone at rest.  In humans, supplementation lowered biomarkers for stress during math testing.  



Further facts:

            Although theanine falls into the biological class of amino acids, our bodies never incorporate it into proteins.  It is therefore non-essential for metabolic function which is good since it is uncommon in our diets.  Green tea (multiple) and some mushrooms produce this amino acid and provide dietary sources (Examine, Casimir).  Green tea contains 25-60mg per 6 oz serving of tea (Nobre).  Supplements may derive their theanine from these natural sources or utilize synthetic methods from glutamine and ethylamine.  Suntheanine®, a patented form (patent link) consisting of 99% L-theanine, has served as a standardized form in many studies and can be found in numerous supplement versions.

            Kinetics:  Theanine crosses the blood brain barrier when given orally (Terashima).  The levels rise within 1 hour and remains elevated up to 5 hours (Terashima). 

            Effects:  Alpha waves are increased (refer to Examine summary article for lists)  These alpha brain waves have been found associated with relaxation states in other studies (Pfurtscheller, Kelly et al).   These alpha waves also seem associated with increased attention.

How to take:

            Theanine can be consumed in green tea drinks and may be better absorbed in that form.  Supplementation provides higher doses to the intestine and ultimately produces higher levels in the blood.



Potential Side Effects of theanine usage:

  1. Allergic reactions: As with nearly any therapy, anyone can develop allergies to any chemical we give them.  Severe reactions are extremely rare with theanine, but low-grade subtle effects may occur.   
  2. Otherwise, low risk of side effects beyond nausea.
  3. In testing, theanine did not appear to create any cancer risk.




            Unlikely to react negatively with other therapies.

            May increase effects of GABA therapy.




General Background and Further Facts:

L-theanine, unique amino acid of tea, and its metabolism, health effects, and safety.  Türközü D, Şanlier N.  Crit Rev Food Sci Nutr. 2017 May 24;57(8):1681-1687. doi: 10.1080/10408398.2015.1016141. Review.  PMID:     26192072

L-Theanine: properties, synthesis and isolation from tea.  Vuong QV, Bowyer MC, Roach PD.  J Sci Food Agric. 2011 Aug 30;91(11):1931-9. doi: 10.1002/jsfa.4373. Epub 2011 Mar 29. Review.  PMID:    21735448

Yamada T, et al. Theanine, r-glutamylethylamide, increases neurotransmission concentrations and neurotrophin mRNA levels in the brain during lactation. Life Sci. (2007)

Nobre AC, Rao A, Owen GN. L-theanine, a natural constituent in tea, and its effect on mental state. Asia Pac J Clin Nutr. (2008)

CASIMIR J, JADOT J, RENARD M. Separation and characterization of N-ethyl-gamma-glutamine from Xerocomus badius. Biochim Biophys Acta. (1960)

Terashima T, Takido J, Yokogoshi H. Time-dependent changes of amino acids in the serum, liver, brain and urine of rats administered with theanine. Biosci Biotechnol Biochem. (1999)


Patent Link and Company information:

Process for producing theanine WO 2004016798 A1.

Suntheanine: A pure and safe L-theanine dietary supplement for relaxation and stress relief.



Pfurtscheller G. Event-related synchronization (ERS): an electrophysiological correlate of cortical areas at rest. Electroencephalogr Clin Neurophysiol. (1992)

Kelly SP, et al. Increases in alpha oscillatory power reflect an active retinotopic mechanism for distracter suppression during sustained visuospatial attention. J Neurophysiol. (2006)


Sleep & Anxiety:

L-theanine, unique amino acid of tea, and its metabolism, health effects, and safety. Review article  Türközü D, et al. Crit Rev Food Sci Nutr. 2017.

Lyon MR, Kapoor MP, Juneja LR. The effects of L-theanine (Suntheanine®) on objective sleep quality in boys with attention deficit hyperactivity disorder (ADHD): a randomized, double-blind, placebo-controlled clinical trial. Altern Med Rev. (2011)

Curr Pharm Des. 2017;23(19):2876-2905. doi: 10.2174/1381612823666170105151800.  Effect of Green Tea Phytochemicals on Mood and Cognition.  Dietz C, Dekker M.

Nutr Rev. 2014 Aug;72(8):507-22. doi: 10.1111/nure.12120. Epub 2014 Jun 19.  Acute effects of tea constituents L-theanine, caffeine, and epigallocatechin gallate on cognitive function and mood: a systematic review and meta-analysis.  Camfield DA, Stough C, Farrimond J, Scholey AB.


Asia Pac J Clin Nutr. 2008;17 Suppl 1:167-8.  L-theanine, a natural constituent in tea, and its effect on mental state.  Nobre AC, Rao A, Owen GN.



Cognitive enhancement

Review Neuroprotective effects of theanine and its preventive effects on cognitive dysfunction.  Kakuda T Pharmacol Res. 2011 Aug; 64(2):162-8

Protective effect of the green tea component, L-theanine on environmental toxins-induced neuronal cell death. Cho HS, Kim S, Lee SY, Park JA, Kim SJ, Chun HS  Neurotoxicology. 2008 Jul; 29(4):656-62.

Park SK, et al. A combination of green tea extract and l-theanine improves memory and attention in subjects with mild cognitive impairment: a double-blind placebo-controlled study. J Med Food. (2011)



Ritsner MS, et al. L-theanine relieves positive, activation, and anxiety symptoms in patients with schizophrenia and schizoaffective disorder: an 8-week, randomized, double-blind, placebo-controlled, 2-center study. J Clin Psychiatry. (2011)



Kim TI, et al. l-Theanine, an amino acid in green tea, attenuates beta-amyloid-induced cognitive dysfunction and neurotoxicity: reduction in oxidative damage and inactivation of ERK/p38 kinase and NF-kappaB pathways. Free Radic Biol Med. (2009)


Takeda A, et al. Unique induction of CA1 LTP components after intake of theanine, an amino acid in tea leaves and its effect on stress response. Cell Mol Neurobiol. (2012)

Tamano H, et al. Preventive effect of theanine intake on stress-induced impairments of hippocamapal long-term potentiation and recognition memory. Brain Res Bull. (2013)

Tian X, et al. Protective effect of l-theanine on chronic restraint stress-induced cognitive impairments in mice. Brain Res. (2013)

Kimura K, et al. L-Theanine reduces psychological and physiological stress responses. Biol Psychol. (2007)



Mutagenicity test of food additives with Salmonella typhimurium TA97 and TA102.

About the Author :

Leave a Comment