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Clinical data
SynonymsL-Theanine, N-Ethyl-L-glutamine
Routes of
Legal status
Legal status
  • Legal everywhere
CAS Number
PubChem CID
E number{{#property:P628}}
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Chemical and physical data
Molar mass174.20 g/mol
3D model (JSmol)
Melting point117 °C (242.6 °F)

Theanine is an amino acid commonly found in tea (infusions of Camellia sinensis). Theanine is related to glutamine, and can cross the blood-brain barrier.[1] Because it can enter the brain, theanine has psychoactive properties.[2] Theanine has been shown to reduce mental and physical stress[3] and may produce feelings of relaxation.[4]

Theanine is speculated to produce these effects by increasing the level of gamma-aminobutyric acid (GABA) production. Theanine increases brain serotonin, dopamine, GABA levels and has micromolar affinities for AMPA, Kainate and NMDA receptors.[5] It has also been found that injecting spontaneously hypertensive mice with theanine significantly lowered levels of 5-hydroxyindole in the brain.[6] Researchers also speculate that it may inhibit glutamic acid excitotoxicity.[5] Theanine also promotes alpha wave production in the brain.[2]

Studies on test rats have shown that even repeated, extremely high doses of theanine cause little to no harmful psychological or physical effects.[7]

L-theanine may help the body's immune system response when fighting infection by boosting the disease-fighting capacity of gamma delta T cells. The study, published in 2003 by the Brigham and Women's Hospital, included a four-week trial with 11 coffee drinkers and 10 tea drinkers, who consumed 600 milliliters of coffee or black tea daily. Blood sample analysis found that the production of anti-bacterial proteins was up to five times higher in the tea-drinkers, an indicator of a stronger immune response.[8]

Recently, marketing campaigns from tea companies have been emphasizing the natural presence of L-theanine in their tea and that L-theanine boosts the production of alpha brainwaves. [9]

See also


  1. Yokogoshi H, Kobayashi M, Mochizuki M, Terashima T (1998). "Effect of theanine, r-glutamylethylamide, on brain monoamines and striatal dopamine release in conscious rats". Neurochem Res. 23 (5): 667–73. PMID 9566605.
  2. 2.0 2.1 Gomez-Ramirez M. "The Deployment of Intersensory Selective Attention: A High-density Electrical Mapping Study of the Effects of Theanine". Clin Neuropharmacol. 30 (1): 25–38. PMID 17272967.
  3. Kimura K, Ozeki M, Juneja L, Ohira H (2007). "L-Theanine reduces psychological and physiological stress responses". Biol Psychol. 74 (1): 39–45. PMID 16930802.
  4. Lu K, Gray M, Oliver C, Liley D, Harrison B, Bartholomeusz C, Phan K, Nathan P (2004). "The acute effects of L-theanine in comparison with alprazolam on anticipatory anxiety in humans". Hum Psychopharmacol. 19 (7): 457–65. PMID 15378679.
  5. 5.0 5.1 Nathan P, Lu K, Gray M, Oliver C (2006). "The neuropharmacology of L-theanine(N-ethyl-L-glutamine): a possible neuroprotective and cognitive enhancing agent". J Herb Pharmacother. 6 (2): 21–30. PMID 17182482.
  6. Yokogoshi H, Kato Y, Sagesaka YM, Takihara-Matsuura T, Kakuda T, Takeuchi N (1995). "Reduction effect of theanine on blood pressure and brain 5-hydroxyindoles in spontaneously hypertensive rats". Biosci Biotechnol Biochem. 59 (4): 615–618. PMID 7539642.
  7. Borzelleca J, Peters D, Hall W (2006). "A 13-week dietary toxicity and toxicokinetic study with L-theanine in rats". Food Chem Toxicol. 44 (7): 1158–66. PMID 16759779.
  8. Kamath A, Wang L, Das H, Li L, Reinhold V, Bukowski J (2003). "Antigens in tea-beverage prime human Vgamma 2Vdelta 2 T cells in vitro and in vivo for memory and nonmemory antibacterial cytokine responses". Proc Natl Acad Sci U S A. 100 (10): 6009–14. PMID 12719524.
  9. Lipton's L-theanine page

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