2-Amino-4- (ethylcarbamoyl) Butyric Acid, 5-N-ethylglutamine, Gamma-ethylamino-L-glutamic acid, Gamma-glutamylethylamide, Gamma-N-ethylglutamine, L-gamma-glutamylethylamide, L-Theanine, L-Théanine, N-Éthyl-L-Glutamine, Teanina, Théanine.
Overview InformationTheanine is an amino acid found in tea. It is also found in some mushrooms.
Theanine is used to improve mental function. It is also used for anxiety, mental impairment, stress, and other conditions, but there is no good scientific evidence to support these uses.
How does it work?Theanine has a chemical structure very similar to glutamate, a naturally occurring amino acid in the body that helps transmit nerve impulses in the brain. Some of the effects of theanine appear to be similar to glutamate, and some effects seem to block glutamate.
Uses & Effectiveness
Possibly Effective for
- Memory and thinking skills (cognitive function). Taking theanine might help healthy people stay focused on a task over long periods of time. It might also help people with lower thinking skills perform tasks that require them to find words in a specific category. But it doesn't seem to improve other measures of memory or thinking. Some research has assessed the effects of theanine along with caffeine. This combination seems to improve a person's ability to switch attention between different tasks. It's unclear if the combination works better than either single ingredient.
Insufficient Evidence for
- Ability to pay attention. Early research shows that taking 200 mg of theanine before a test improves attention. Taking theanine with caffeine seems to work better than taking theanine alone. Taking lower doses of theanine might not improve attention.
- Attention deficit-hyperactivity disorder (ADHD). Some early research shows that taking theanine might improve memory and thinking skills, but not attention or impulse control, in children with ADHD. Other early research shows that taking theanine twice daily for 6 weeks increases restful sleep and decreases nightly activity during sleep in boys ages 8-12 with ADHD.
- Diarrhea caused by cancer drug treatment. Taking a product containing cysteine and theanine might reduce diarrhea and loss of appetite caused by some cancer drugs in people with colon cancer. But it doesn't seem to reduce these side effects of cancer drugs in people with stomach cancer. It also doesn't seem to reduce diarrhea caused by all cancer drugs.
- Decline in memory and thinking skills in older people that is more than what is normal for their age. Early research shows that taking a product containing theanine and green tea might improve memory or attention in people with mild mental impairment.
- Depression. Early research shows that taking theanine by mouth at bedtime for 8 weeks decreases symptoms and improves sleep in people with depression.
- Flu (influenza). Early research shows that taking a combination of green tea extract plus theanine daily for 5 months may lower the risk of developing the flu.
- Schizophrenia. Some early research shows that taking theanine by mouth along with antipsychotic drugs improves positive symptoms but not negative symptoms of schizophrenia. Other early research shows that taking theanine with pregnenolone and antipsychotic drugs improves negative symptoms but not positive symptoms. More research is needed to determine the effects, if any, of theanine on symptoms of schizophrenia.
- Stress. The effects of theanine on stress are conflicting. Some early research shows that taking 200 mg of theanine before an exam reduces anxiety and may prevent blood pressure from increasing due to stress. Other early research shows that taking 200 mg of theanine twice daily before and during pharmacy practice decreases stress levels. However, another early study shows that taking 200 mg of theanine helps promote tranquility in people who are already relaxed. But it doesn't work in people who are stressed. Reasons for the conflicting results are not clear.
- Alzheimer disease.
- High blood pressures.
- Other conditions.
Side Effects & SafetyWhen taken by mouth: Theanine is POSSIBLY SAFE when taken by mouth, short-term. Doses of up to 400 mg of theanine daily have been safely used for 8 weeks. A specific product containing theanine and other green tea ingredients has also been used safely once daily for up to 5 months. It is unknown if theanine is safe when used for longer periods of time. Theanine may cause mild adverse effects, such as headache or sleepiness.
Special Precautions & Warnings:Pregnancy and breast-feeding: There isn't enough reliable information to know if theanine is safe to use when pregnant or breast-feeding. Stay on the safe side and avoid use.
Children: Theanine is POSSIBLY SAFE for children when taken by mouth, short-term. Doses of 200 mg of theanine have been safely used twice daily for up to 6 weeks in boys aged 8-12 years.
Low blood pressure: Theanine might lower blood pressure. In theory, theanine might increase the risk of blood pressure dropping too low in people prone to low blood pressure. If you have low blood pressure, discuss theanine with your healthcare provider before starting it.
Be cautious with this combination
Medications for high blood pressure (Antihypertensive drugs) interacts with THEANINE
Theanine seems to decrease blood pressure. Taking theanine along with medications for high blood pressure might cause your blood pressure to go too low.
Some medications for high blood pressure include captopril (Capoten), enalapril (Vasotec), losartan (Cozaar), valsartan (Diovan), diltiazem (Cardizem), Amlodipine (Norvasc), hydrochlorothiazide (HydroDiuril), furosemide (Lasix), and many others.
Stimulant drugs interacts with THEANINE
Stimulant drugs speed up the nervous system. By speeding up the nervous system stimulant medications can make you feel jittery and speed up your heartbeat. Theanine might work to slow down the nervous system. Taking theanine along with stimulant medications might decrease the effectiveness of stimulant medications.
Some stimulant drugs include diethylpropion (Tenuate), epinephrine, phentermine (Ionamin), pseudoephedrine (Sudafed), and many others.
The following doses have been studied in scientific research:
- For memory and thinking skills (cognitive function): A single dose of 100 mg of theanine before a test has been used. Theanine 200 mg daily for 4 weeks has been used. Theanine has also been used in combination with caffeine. Combination doses have ranged from 30-100 mg of caffeine and 12-100 mg of theanine.
- Borzelleca, J. F., Peters, D., and Hall, W. A 13-week dietary toxicity and toxicokinetic study with l-theanine in rats. Food Chem.Toxicol. 2006;44(7):1158-1166. View abstract.
- Egashira, N., Ishigami, N., Pu, F., Mishima, K., Iwasaki, K., Orito, K., Oishi, R., and Fujiwara, M. Theanine prevents memory impairment induced by repeated cerebral ischemia in rats. Phytother.Res 2008;22(1):65-68. View abstract.
- Giesbrecht, T., Rycroft, J. A., Rowson, M. J., and De Bruin, E. A. The combination of L-theanine and caffeine improves cognitive performance and increases subjective alertness. Nutr Neurosci. 2010;13(6):283-290. View abstract.
- Haskell, C. F., Kennedy, D. O., Milne, A. L., Wesnes, K. A., and Scholey, A. B. The effects of L-theanine, caffeine and their combination on cognition and mood. Biol.Psychol. 2008;77(2):113-122. View abstract.
- Kakuda, T. Neuroprotective effects of the green tea components theanine and catechins. Biol Pharm Bull 2002;25(12):1513-1518. View abstract.
- Kakuda, T., Nozawa, A., Sugimoto, A., and Niino, H. Inhibition by theanine of binding of [3H]AMPA, [3H]kainate, and [3H]MDL 105,519 to glutamate receptors. Biosci.Biotechnol.Biochem. 2002;66(12):2683-2686. View abstract.
- Kamath, A. B., Wang, L., Das, H., Li, L., Reinhold, V. N., and Bukowski, J. F. 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 5-13-2003;100(10):6009-6014. View abstract.
- Kimura, K., Ozeki, M., Juneja, L. R., and Ohira, H. L-Theanine reduces psychological and physiological stress responses. Biol Psychol. 2007;74(1):39-45. View abstract.
- Matsumoto, K., Yamada, H., Takuma, N., Niino, H., and Sagesaka, Y. M. Effects of green tea catechins and theanine on preventing influenza infection among healthcare workers: a randomized controlled trial. BMC.Complement Altern.Med. 2011;11:15. View abstract.
- Rogers, P. J., Smith, J. E., Heatherley, S. V., and Pleydell-Pearce, C. W. Time for tea: mood, blood pressure and cognitive performance effects of caffeine and theanine administered alone and together. Psychopharmacology (Berl) 2008;195(4):569-577. View abstract.
- Sadzuka, Y., Sugiyama, T., Suzuki, T., and Sonobe, T. Enhancement of the activity of doxorubicin by inhibition of glutamate transporter. Toxicol.Lett 9-15-2001;123(2-3):159-167. View abstract.
- Sugiyama, T. and Sadzuka, Y. Theanine and glutamate transporter inhibitors enhance the antitumor efficacy of chemotherapeutic agents. Biochim.Biophys.Acta 12-5-2003;1653(2):47-59. View abstract.
- Sugiyama, T. and Sadzuka, Y. Theanine, a specific glutamate derivative in green tea, reduces the adverse reactions of doxorubicin by changing the glutathione level. Cancer Lett. 8-30-2004;212(2):177-184. View abstract.
- Sugiyama, T., Sadzuka, Y., Nagasawa, K., Ohnishi, N., Yokoyama, T., and Sonobe, T. Membrane transport and antitumor activity of pirarubicin, and comparison with those of doxorubicin. Jpn J Cancer Res 1999;90(7):775-780. View abstract.
- Terashima, T., Takido, J., and Yokogoshi, H. Time-dependent changes of amino acids in the serum, liver, brain and urine of rats administered with theanine. Biosci.Biotechnol.Biochem. 1999;63(4):615-618. View abstract.
- Yang, Q. S., Xu, P. X., Li, Y. H., Jiang, S., Zhang, X., and Xue, M. [Effects of theanine and houpu extract in 7-day chick social separation-stress procedure]. Zhongguo Zhong.Yao Za Zhi. 2007;32(19):2040-2043. View abstract.
- Yokogoshi, H., Kato, Y., Sagesaka, Y. M., Takihara-Matsuura, T., Kakuda, T., and Takeuchi, N. Reduction effect of theanine on blood pressure and brain 5-hydroxyindoles in spontaneously hypertensive rats. Biosci.Biotechnol.Biochem. 1995;59(4):615-618. View abstract.
- Camfield DA, Stough C, Farrimond J, Scholey AB. Actue effects of tea constituents L-theanine, caffeine, and epigallocatechin gallate on cognitive function and mood: a systematic review and meta-analysis. Nutr Rev. 2014;72(8):507-522. View abstract.
- Dodd FL, Kennedy DO, Riby LM, Haskell-Ramsay CF. A double-blind, placebo-controlled study evaluating the effects of caffeine and L-theanine both alone and in combination on cerebral blood flow, cognition and mood. Psychopharmacology. 2015;232(14):2563-2576. View abstract.
- Einöther SJ, Martens VE, Rycroft JA, De Bruin EA. L-theanine and caffeine improve task switching but not intersensory attention or subjective alertness. Appetite 2010;54(2):406-9. View abstract.
- Foxe JJ, et al. Assessing the effects of caffeine and theanine on the maintenance of vigilance during a sustained attention task. Neuropharmacology. 2012;62(7):2320-2327. View abstract.
- Graham HN. Green tea composition, consumption, and polyphenol chemistry. Prev Med 1992;21:334-50. View abstract.
- Hamaguchi R, Tsuchiya T, Miyata G, et al. Efficacy of oral administration of cystine and theanine in colorectal cancer patients undergoing capecitabine-based adjuvant chemotherapy after surgery: a multi-institutional, randomized, double-blinded, placebo-controlled, phase II trial (JORTC-CAM03). Support Care Cancer. 2019. View abstract.
- Hidese S, Ogawa S, Ota M, et al. Effects of L-theanine administration on stress-related symptoms and cognitive functions in healthy adults: A randomized controlled trial. Nutrients. 2019;11(10). pii: E2362. View abstract.
- Hidese S, Ota M, Wakabayashi C, et al. Effects of chronic l-theanine administration in patients with major depressive disorder: an open-label study. Acta Neuropsychiatr 2017;29(2):72-9. View abstract.
- Kahathuduwa CN, Dassanayake TL, Amarakoon AMT, Weerasinghe VS. effects of theanine, caffeine and theanine-caffeine combination on attention. Nutr Neurosci 2017;20(6):369-77. View abstract.
- Kahathuduwa CN, Wakefield S, West BD, et al. Effects of L-theanine-caffeine combination on sustained attention and inhibitory control among children with ADHD: a proof-of-concept neuroimaging RCT. Sci Rep 2020;10(1):13072. View abstract.
- Kakuda T, Nozawa A, Unno T, et al. Inhibiting effects of theanine on caffeine stimulation evaluated by EEG in the rat. Biosci Biotechnol Biochem 2000;64:287-93. View abstract.
- Kakuda T, Yanase H, Utsunomiya K, et al. Protective effect of gamma-glutamylethylamide (theanine) on ischemic delayed neuronal death in gerbils. Neurosci Lett 2000;289:189-92. View abstract.
- Kardashev A, Ratner Y, Ritsner MS.Add-on pregnenolone with L-theanine to antipsychotic therapy relieves negative and anxiety symptoms of schizophrenia: an 8-week, randomized, double-blind, placebo-controlled trial. Clin Schizophr Relat Psychoses. 2018;12(1):31-41. doi: 10.3371/CSRP.KARA.070415. View abstract.
- Kawada S, Kobayashi K, Ohtani M, Fukusaki C. Cystine and theanine supplementation restores high-intensity resistance exercise-induced attenuation of natural killer cell activity in well-trained men. J Strength Cond Res 2010;24(3):846-51. View abstract.
- Kelly SP, Gomez-Ramirez M, Montesi JL, Foxe JJ. L-theanine and caffeine in combination affect human cognition as evidenced by oscillatory alpha-band activity and attention task performance. J Nutr 2008;138(8):1572S-1577S. View abstract.
- Kimura R, Murata T. Effect of theanine on norepinephrine and serotonin levels in rat brain. Chem Pharm Bull 1986;34:3053-57.
- Lin L, Zeng L, Liu A, et al. L-theanine regulates glucose, lipid, and protein metabolism via insulin and AMP-activated protein kinase signaling pathways. Food Funct. 2020;11(2):1798-1809. View abstract.
- Lu K, Gray MA, Oliver C, et al. The acute effects of L-theanine in comparison with alprazolam on anticipatory anxiety in humans. Hum Psychopharmacol 2004;19:457-65. View abstract.
- 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;16(4):348-354. View abstract.
- Miodownik C, Maayan R, Ratner Y, et al. Serum 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 patients. Clin Neuropharmacol 2011;34(4):155-60. View abstract.
- Miyachi T, et al. Perioperative oral administration of cystine and theanine enhances recovery after distal gastrectomy: a prospective randomized trial. JPEN. 2013;37(3):384-391. View abstract.
- Murakami S, Kurihara S, Koikawa N, et al. Effects of oral supplementation with cystine and theanine on the immune function of athletes in endurance exercise: randomized, double-blind, placebo-controlled trial. Biosci Biotechnol Biochem 2009;73(4):817-21. View abstract.
- Owen GN, Parnell H, De Bruin EA, Rycroft JA. The combined effects of L-theanine and caffeine on cognitive performance and mood. Nutr Neurosci 2008;11(4):193-8. View abstract.
- Park SK, Jung IC, Lee WK, 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;14(4):334-43. View abstract.
- Ritsner MS, Miodownik C, Ratner Y, 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;72(1):34-42. View abstract.
- Sadzuka Y, Sugiyama T, Miyagishima A, et al. The effects of theanine, as a novel biochemical modulator, on the antitumor activity of adriamycin. Cancer Lett 1996;105:203-9. View abstract.
- Sadzuka Y, Sugiyama T, Sonobe T. Efficacies of tea components on doxorubicin induced antitumor activity and reversal of multidrug resistance. Toxicol Lett 2000;114:155-62. View abstract.
- Sadzuka Y, Sugiyama T, Sonobe T. Improvement of idarubicin induced antitumor activity and bone marrow suppression by theanine, a component of tea. Cancer Lett 2000;158:119-24. View abstract.
- Sakato Y. The chemical constituents of tea: III. A new amide theanine. Nippon Nogei Kagakukaishi 1949;23:262-267.
- Scheid L, et al. Kinetics of L-theanine uptake and metabolism in healthy participants are comparable after ingestion of L-theanin via capsules and green tea. J Nutr. 2012;142(12):2091-2096. View abstract.
- Sugiyama T, Sadzuda Y. Enhancing effects of green tea components on the antitumor activity of adriamycin against M5076 ovarian sarcoma. Cancer Lett 1998;133:19-26. View abstract.
- Sugiyama T, Sadzuka Y, Tanaka K, Sonobe T. Inhibition of glutamate transporter by theanine enhances the therapeutic efficacy of doxorubicin. Toxicol Lett 2000:121:89-96. View abstract.
- Sugiyama T, Sadzuka Y. Combination of theanine with doxorobucin inhibits hepatic metastasis of M5076 ovarian sarcoma. Clin Cancer Res 1999;5:413-6. View abstract.
- Tsuchiya T, Honda H, Oikawa M, et al. Oral administration of the amino acids cystine and theanine attenuates the adverse events of S-1 adjuvant chemotherapy in gastrointestinal cancer patients. Int J Clin Oncol 2016;21(6):1085-90. View abstract.
- Unno K, et al. Anti-stress effect of theanine on students during pharmacy practice: positive correlation among salivary a-amylase activity, trait anxiety and subjective stress. Pharmacol Biochem Behav. 2013;111:128-135. View abstract.
- Williams J, Kellett J, Roach PD, et al. L-theanine as a functional food additive: its role in disease prevention and health promotion. Beverages 2016;2(2):13.
- Williams J, McKune AJ, Georgousopoulou EN, et al. The effect of L-theanine incorporated in a functional food product (mango sorbet) on physiological responses in healthy males: a pilot randomised controlled trial. Foods 2020;9(3):371. View abstract.
- Yokogoshi H, Kobayashi M. Hypotensive effect of gamma-glutamylethylamide in spontaneously hypertensive rats. Life Sci 1998;62:1065-8. View abstract.
- Yokogoshi H, Mochizuki M, Saitoh K. Theanine-induced reduction of brain serotonin concentration in rats. Biosci Biotechnol Biochem 1998;62:816-7. View abstract.
- Yokozawa T, Dong E. Influence of green tea and its three major components upon low-density lipoprotein oxidation. Exp Toxicol Pathol 1997;49:329-35. View abstract.
- Yokozawa T, Oura H, Nakagawa H, et al. Effects of a component of green tea on the proliferation of vascular smooth muscle cells. Biosci Biotechnol Biochem 1995;59:2134-6. View abstract.
- Yoto A, Motoki M, Murao S, Yokogoshi H. Effects of L-theanine or caffeine intake on changes in blood pressure under physical and psychological stresses. J Physiol Anthropol. 2012;31:28. View abstract.
- Zheng G, Sayama K, Okubo T, et al. Anti-obesity effects of three major components of green tea, catechins, caffeine and theanine, in mice. In Vivo 2004;18:55-62. View abstract.
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