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The Gift in your Cup of Tea: L-Theanine


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L-theanine, that by-now famous constituent of green tea, can be like your best friend –calming you down and lifting your mood with a smile. Theanine was first studied as an anxiolytic – it was shown to reduce anxiety.[1] Calmness in a tea cup! Theanine was, in fact, found to increase the alpha waves in your brain – those waves that relax the mind without causing sedative effects.[2] Alpha waves are always associated with calm and meditation, but also with increases in your ability to focus and be alert. So good for students just before an exam!

Your Primary Inhibitory Neurotransmitter, GABA, and Theanine

Another way in which theanine calms you down is by increasing your primary inhibitory neurotransmitter, GABA[3] and a third way is that it counters the stimulatory effects of caffeine.[4] However, theanine, and by association, green tea, is now known to do a lot more for you! It may be able to reduce increases in blood pressure and heart rate during acute stress in folks who, shall we say, are high-strung.[5],[6] It has been shown to reduce the amyloid plaques in the brain—plaques associated with worsening Alzheimer’s Disease,[7] and improve cognition and memory. Theanine can also protect the brain from various forms of toxic insults and free radical damage.[8],[9],[10] We know, too, that it helps reduce the damage that elevated glutamate does – a condition called excitotoxicity, and so protects neurons from excessive glutamate stimulation.[11],[12] And the good news is that it provides you with all these benefits in the amounts of tea you would normally drink—a couple cups, or take in supplement form (50-200mg).

So relax, have yourself a cup of green tea and know that you are doing your brain good!



[1] Lardner AL. (2014). Neurobiological effects of the green tea constituent theanine and its potential role in the treatment of psychiatric and neurodegenerative disorders. Nutr Neurosci. Jul;17(4):145-55.


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


[3] Nathan PJ, Lu K, Gray M, et al. (2006). The neuropharmacology of L-theanine(N-ethyl-L-glutamine): a possible neuroprotective and cognitive enhancing agent. J Herb Pharmacother. 6(2):21-30.


[4] Eschenauer G, Sweet BV. (2006). Pharmacology and therapeutic uses of theanine. Am J Health Syst Pharm. Jan 1;63(1):26, 28-30.


[5] Yoto A, Motoki M, Murao S, et al. (2012). Effects of L-theanine or caffeine intake on changes in blood pressure under physical and psychological stresses. J Physiol Anthropol.31:28.


[6] Siamwala JH, Dias PM, Majumder S, et al. (2013). L-theanine promotes nitric oxide production in endothelial cells through eNOS phosphorylation. J Nutr Biochem. 24(3):595-605.


[7] Kim TI, Lee YK, Park SG, et al. (2009). 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. 47(11):1601-10.


[8] Cho HS, Kim S, Lee SY, et al. (2008). Protective effect of the green tea component, L-theanine on environmental toxins-induced neuronal cell death. Neurotoxicology. 29(4):656-62.


[9] Thangarajan S, Deivasigamani A, Natarajan SS, et al. (2014). Neuroprotective activity of L-theanine on 3-nitropropionic acid-induced neurotoxicity in rat striatum. Int J Neurosci. 124(9):673-84.


[10] Sumathi T, Shobana C, Thangarajeswari M, et al. (2015). Protective effect of L-Theanine against aluminium induced neurotoxicity in cerebral cortex, hippocampus and cerebellum of rat brain – histopathological, and biochemical approach. Drug Chem Toxicol. 38(1):22-31.


[11] Nathan PJ, op. cit.


[12] Zukhurova M, Prosvirnina M, Daineko A, et al. (2013). L-theanine administration results in neuroprotection and prevents glutamate receptor agonist-mediated injury in the rat model of cerebral ischemia-reperfusion.Phytother Res. 27(9):1282-7.

Clinical Contributor

[starbox id = “Ramona Richard NC MS”]

Ramona Richard, MS, NC

Ramona Richard, MS, NC

Ramona Richard graduated with honors from the University of California with a Bachelor’s Degree in psychology and graduated summa cum laude with a Master’s Degree in Health and Nutrition Education. She also holds a Standard Designated Teaching Credential from the State of California, is a California state-certified Nutrition Consultant and a member of the National Association of Nutrition Professionals.

Ramona has participated in nutrition education in both public and private venues, including high school and college presentations, radio and public speaking for the past 20 years. She is the owner of Radiance, a nutrition consulting company, the Director of Education for Sanesco International, and a medical technical writer.

Disclaimer: The information provided is only intended to be general educational information to the public. It does not constitute medical advice. If you have specific questions about any medical matter or if you are suffering from any medical condition, you should consult your doctor or other professional healthcare provider.

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