L-Theanine is an amino acid analogue of glutamate and glutamine found in green tea and in gyokuro leaves, thus demonstrating culinary use (1-2).

Scientific effects

L-Theanine is an amino acid analogue of glutamate and glutamine found in green tea and in gyokuro leaves, thus demonstrating culinary use (1-2).

L-theanine is well absorbed by the body (comparable to green tea) and increases in plasma based in a dose dependent manner. Below is the plasma levels of 100 mg of Theanine after administration in a human subject:

Studies using l-theanine have shown that l-theanine use in humans reduces psychological stress, physiological stress, promotes mental relaxation, decreases anxiety and improves reaction timing by increasing rates of attention. This is further supported by findings conducted on adults that found an increase in alpha waves following Theanine supplementation (3-6).

A study in pharmacy students who took 200 mg of Theanine twice a day (once after breakfast and once after lunch) found that taking Theanine for one week prior to a test decreased levels of salivary alpha-amylase activity (7). Another interesting finding is that they found that people with higher levels of salivary alpha-amylase activity slept less (to be discussed further in reference 13).

Further investigation of Theanine showed that doses of 200-400 mg significantly increases the sensory gating mechanism in humans (8). Sensory gating is essentially mental processes that filter out unnecessary information from someone’s information that is deemed irrelevant by the brain. If someone is interested in learning further, research Mike Posner and his work on visual search, or the theory known as “inhibition of return”; it's interesting when applied to the concept of foraging.

Interestingly enough, however, there are also studies showing that a combination of Theanine and caffeine improves these reaction timing effects, and that the combination of the two results in an improvement of mood, cognition, while attenuating blood pressure increase from caffeine use in adults (9-10). This remained true regardless to whether the task was visual or motor in nature (11).

The relationship between caffeine and Theanine was explored further (12) and it was shown that 50 mg of l-theanine was enough to eliminate the vasoconstrictive and behavioural effects of 75 mg of caffeine (see the table below). It’s important to note that this experiment did not find any significant benefit of Theanine supplementation, but it also used a very minor dose of Theanine (50 mg).

Research in young boys (ages 8-12) diagnosed with ADHD showed that 400 mg of Theanine had a significant effect on sleep efficiency (refer to the figure below); it effectively meant they spent more time asleep at night and woke up less (13).


This makes sense when one recalls that Theanine is anxiolytic in nature. Remember that reference 7 showed us that increased salivary alpha-amylase activity results in less sleep, and that Theanine lowers salivary alpha-amylase activity. Salivary alpha-amylase activity is considered a marker of stress (cortisol).

While there is some debate in the field on how ADHD and cortisol are linked, more recognized papers show that individuals with ADHD (particularly adults) tend to also suffer from higher than normal levels of cortisol (14). It is not surprising that to think that Theanine possibly helped the individuals with ADHD sleep better due to lowering salivary alpha-amylase activity rather than being sedative in nature.


This makes Theanine an excellent addition to any product that is designed to:

  • provide euphoria/ calmness
  • promote relaxation
  • relieve stress

Safety profile

Please consult with a physician before using Theanine. Theanine can be taken any time of day depending on the desired effects. 


  1. "Components of Gyokuro| IPPODO". Ippodo-tea.co.jp. Retrieved from: Components of Gyokuro? IPPODO 
  1. Finger, Andreas; Kuhr, Susanne; Engelhardt, Ulrich (1992). "Chromatography of tea constituents". Journal of Chromatography 624: 309-310. 
  1. Higashiyama, A., Htay, H., Ozeki, M., et al. (2011). Effects of l-theanine on attention and reaction time response. Journal of Functional Foods.3:3(171-178). 
  1. Kimura, K., Ozeki, M., Juneja, L. R., & Ohira, H. (2007). l-Theanine reduces psychological and physiological stress responses. Biological Psychology, 74(1), 39-45. 
  1. KOBAYASHI, K., NAGATO, Y., AOI, N., JUNEJA, L. R., KIM, M., YAMAMOTO, T., & SUGIMOTO, S. (1998). Effects of L-Theanine on the Release of Alpha-Brain Waves in Human Volunteers. Journal of the agricultural chemical society of Japan, 72(2), 153-157. 
  1. Lu, K., Gray, M. A., Oliver, C., Liley, D. T., Harrison, B. J., Bartholomeusz, C. F., Phan, K. L., et al. (2004). The acute effects of L-theanine in comparison with alprazolam on anticipatory anxiety in humans. Human Psychopharmacology, 19(7), 457-465. 
  1. Unno, K., Tanida, N., Ishii, N., Yamamoto, H., Iguchi, K., Hoshino, M., Takeda, A., et al. (2013). Anti-stress effect of theanine on students during pharmacy practice: Positive correlation among salivary α-amylase activity, trait anxiety and subjective stress. Pharmacology Biochemistry and Behavior, 111, 128-135. 
  1. Ota, M., Wakabayashi, C., Matsuo, J., Kino****a, Y., Hori, H., Hattori, K., Sasayama, D., et al. (2014). Effect of L-theanine on sensorimotor gating in healthy human subjects. Psychiatry and Clinical Neurosciences, 68(5), 337-343. Blackwell Publishing. 
  1. 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. 
  1. 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), 113-122. 
  1. Kahathuduwa, C. N., Dassanayake, T. L., Amarakoon, A. M. T., & Weerasinghe, V. S. (2016). Acute effects of theanine, caffeine and theanine-caffeine combination on attention. Nutritional Neuroscience, 1-9. Taylor & Francis. 
  1. Dodd, F. L., Kennedy, D. O., Riby, L. M., & Haskell-Ramsay, C. F. (2015). 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, 232(14), 2563-2576. Springer Verlag. 
  1. Lyon, M., Kapoor, M., and Juneja, L. (2011). The Effects of L-Theanine (Suntheanine) Objective Sleep Quality in Boys with Attention Deficit Hyperactivity Disorder (ADHD): a Randomized, Double-blind, Placebo-controlled Clinical Trial. Altern Med Rev. 16(4): 348-54. 
  1. Corominas-Roso, M., Palomar, G., Ferrer, R., et al. (2015). Cortisol Response to Stress in Adults with Attention Deficit Hyperactivity Disorder.Int J Neuropsychopharmacol. 18(9):v027.


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