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Being Cool On-Demand with L-Theanine

Is your anxiety in control of you? Are you suffering from “Karoshi” – the Japanese term for death by work? Would you like to find a way to slow down, unwind, and recalibrate on-demand? In fact, there is an amino acid found in green tea called L-theanine that can take us down a notch when the buzz of anxiety is trying to take us over the top.

Researchers have found that a sufficient dose of L-theanine washes away anxiety and significantly increases alpha brain wave activity1 which helps you feel calm, cool and focused – on-demand. It does this primarily by influencing the neurotransmitters (brain chemicals) dopamine,2,5 gamma-aminobutyric acid (GABA),6,7 serotonin,8,9 norepinephrine9 and glutamate.10,11 This orchestration of brain chemicals helps to induce a state of wakeful relaxation, heightened mental acuity, and improved concentration, all without drowsiness.4,12 Research even suggests that L-theanine may have applications for immunity21, sleep19,20, premenstrual syndrome (PMS) and attention deficit hyperactivity disorder (ADHD)19.

In Japan they believe so strongly in L-theanine’s anxiety-attenuating effects, that it has been licensed for unlimited use in all foods (except infant food) since 1964. These include chocolate, soft drinks and herbal teas. This is impressive considering that in Japan, food ingredients require extensive testing before approval for unlimited use.

Green Tea for L-Theanine

L-theanine was first isolated from green tea in Japan in 1949, and was later found in the leaves and stems of other teas of the Camellia sinensis13 variety including white and black teas4.

Unfortunately, common green tea sold in the Western hemisphere contains less than 10 mg of L-theanine per cup – a far cry from the 50 to 200mg needed to exert therapeutic benefits as shown in studies.

Best Green Tea Options for L-Theanine

Highest amounts of L-theanine are found in shade-grown, spring-harvested green teas such as gyokuro or matcha. Due to their high L-theanine content, these high quality teas boast the delicious fifth taste called umami which tea tasters rate most highly as it is considered to be the most important determinant of tea quality.

Green tea also contains a powerful polyphenol antioxidant called epigallocatechin gallate (EGCG), which has been shown to prevent stress-related neuronal apotosis (brain cell death) in EGCG-treated cells(3). Unfortunately, L-theanine and EGCG content in green teas are inversely related – with exposure to sun and age, L-theanine content in green tea decreases while EGCG content increases, so you may never get high amounts of both at the same time.

Caffeine + L-Theanine

Together, caffeine and L-theanine – both found in green tea - have been have been highlighted for their synergistically beneficial effects on markers of mental task reaction times15, 16, 17,18 , as well as cognition and mood14. But here’s the catch: most studies used ratios of approximately 2:1 L-theanine (100mg) to caffeine (50mg). In most teas, this ratio is reversed (so caffeine is doubled, L-theanine is halved or even quartered). And while L-theanine mitigates the negative aspects of caffeine, such as anxiety and increased blood pressure, its ability to singularly enhance attention over and above that of caffeine alone, has been repeatedly verified. This is one reason to choose L-theanine supplements over tea because they provide higher, standardized dosages, without caffeine.

When to Use L-Theanine Supplements Instead of Tea

Overall, there are some valid reasons to choose L-theanine supplements over teas:

  • Standardized Dosages. L-theanine content in green teas can fluctuate dramatically from as little as 5mg to 46mg per cup22. For those truly in need of therapeutic effects of L-theanine, supplements provide standardized dosages in sufficient amounts to elicit beneficial effects as shown in studies.

  • No Caffeine. Caffeine content of tea can vary (14 to 61mg per cup23), and can still affect sensitive individuals.

  • Ease of Use. Supplements are easy to take and do not require any preparation. For the person who wakes up at 3am with anxiety, a supplement is more efficient and effective than preparing and consuming 3 to 4 cups of tea.

  • No Environmental Contamination. Although L-theanine is an important tea constituent, L-theanine supplements are made using enzymes in laboratories rather than being extracted from tea leaves. In this way, you don't have to worry about environmental pollution or herbicide use.

  • Cost. Compared to teas, supplements are by far the more inexpensive choice for L-theanine on a per milligram basis.

Dosages & Safety Issues

L-theanine can be taken on an as-needed basis during periods of stress, anxiety and sleeplessness. Suggested dosages range from 50mg to 200mg 2 to 3 times per day with or without food.24 It takes effect within 30 minutes to 2 hours and lasts from 8 to 12 hours.24 To date, there have not been any side effects reported from taking L-theanine, however, always consult with your doctor or pharmacist if taking any medications.


  1. Gomez-Ramirez, M., Higgins, B.A., Rycroft, J.A., Owen, G.N., Mahoney, J., Shpaner, M., & Foxe, J. (2007). The Deployment of Intersensory Selective Attention. Clinical Neuropharmacology, 30(1), 25–38.

  2. Nathan, P., Lu, K., Gray, M., & Oliver, C. (2006). The Neuropharmacology of L-theanine (N-Ethyl-L-Glutamine). Journal of Herbal Pharmacotherapy, 6(2), 21–30.

  3. Choi, Y.T., Jung, C.H., Lee, S.R., Bae, J.H., Baek, W.K., Suh, M.H., Park, J., Park, C.W., & Suh, S.I. (2001). The green tea polyphenol (-)-epigallocatechin gallate attenuates β-amyloid-induced neurotoxicity in cultured hippocampal neurons. Life Science, 70, 603.

  4. Juneja, L.R., Chu, D.C., Okubo, T., Nagato, Y., & Yokogoshi, H. (1999). L-theanine - a unique amino acid of green tea and its relaxation effect in humans. Trends in Food Science & Technology, 10(2), 199–204.

  5. Yokogoshi, H., Kobayashi, M., Mochizuki, M., & Terashima, T. (1998). Effect of theanine, r-glutamylethylamide, on brain monoamines and striatal dopamine release in conscious rats. Neurochemical Research, 23(5), 667-73.

  6. Kimura, R. & Murata, T. (1971). Influence of alkylamides of glutamic acid and related compounds on the central nervous system. I. Central depressant effect of theanine. Chemical and Pharmaceutical Bulletin (Tokyo), 19(6), 1257-61.

  7. Alternative Medicine Review (2007). Gamma-Aminobutyric Acid (GABA), Monograph. Alternative Medicine Review, 12(3), 274-9.

  8. Yokogoshi, H., Mochizuki, M., & Saitoh, K. (1998). Theanine-induced reduction of brain serotonin concentration in rats. Bioscience Biotechnology and Biochemistry, 62(4), 816-7.

  9. Kimura, R. & Murata T. (1986). Effect of theanine on norepinephrine and serotonin levels in rat brain. Chemical & Pharmaceutical Bulletin, 34(7), 3053-7.

  10. Kakuda, T. (2002). Neuroprotective effects of green tea components theanine and catechins. Biological & Pharmaceutical Bulletin, 25(12), 1513-8.

  11. Kimura, K., Ozeki, M., Juneja, L.R., & Ohira, H. (2007). L-theanine reduces psychological and physiological stress responses. Biological Psychology, 74(1), 39-45.

  12. Nobre, A.C., Rao, A., & Owen, G.N. (2008). L-theanine, a natural constituent in tea, and its effect on mental state. Asia Pacific Journal of Clinical Nutrition, 17S, 167-8

  13. Finger, A., Kuhr, S., & Engelhardt, U. (1992). Chromatography of tea constituents. Journal of Chromatography, 624, 309-310.

  14. Yoto, A., Motoki, M., Murao, S., & Yokogoshi, H. (2012). Effects of L-theanine or caffeine intake on changes in blood pressure under physical and psychological stresses. Journal of Physiological Anthropology, 31(1), 28.

  15. Haskell, C.F., Kennedy, D.O., Milne, A.L., Wesnes, K.A., & Scholey, A.B. (2008). The effects of L-theanine, caffeine and their combination on cognition and mood. Biological Psychology, 77(2), 113-22.

  16. Einöther, S.J.L., Martens, V.E.G., Rycroft, J.A., & DeBruin, E.A. (2010). L-theanine and caffeine improve task switching but not intersensory attention or subjective alertness. Appetite, 54(2), 406-9.

  17. Bryan, Janet (2008). Psychological effects of dietary components of tea: Caffeine and L-theanine. Nutrition Reviews, 66(2), 82-90.

  18. Kelly, S.P., Gomez-Ramirez, M., Montesi, J.L., & Foxe, J.J. (2008). L-theanine and caffeine in combination affect human cognition as evidenced by oscillatory alpha-band activity and attention task performance. The Journal of Nutrition, 138(8), 1572S–1577S.

  19. Lyon, M.R., Kapoor, M.P., & Juneja, L.R. (2011). 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. Alternative Medicine Review, 16(4), 348-54.

  20. Barrett, J.R., Tracy, D.K., & Giaroli, G. (2013). To sleep or not to sleep: a systematic review of the literature of pharmacological treatments of insomnia in children and adolescents with attention-deficit/hyperactivity disorder. Journal of Child and Adolescent Psychopharmacology, 23(10), 640-7.

  21. Bukowski, J.F., & Percival, S.S. (2008). L-theanine intervention enhances human gammadeltaT lymphocyte function. Nutrition Reviews, 66(2), 96-102.

  22. Keenan, E.K., Finnie, M.D.A., Jones, P.S., Rogers, P.J., & Priestley, C.M. (2011). How much theanine in a cup of tea? Effects of tea type and method of preparation. Food Chemistry, 125(2), 588-594.

  23. Chin, J.M., Merves, M.L., Goldberger, B.A., Sampson-Cone, A., & Cone, E.J. (2008). Caffeine content of brewed teas. Journal of Analytical Toxicology, 32(8), 702-4.

  24. Cooper, R. (2005). Medicinal benefits of green tea. Journal of Alternative and Complementary Medicine, 11, 521-528.​

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