If you haven’t heard of L-Theanine, then you might be surprised to know that this amino acid has some pretty beneficial actions on the body. Found in green tea, L-Theanine is an amino acid that can help improve cognitive performance, calm the mind and enhance mental alertness.

But what exactly is it and what does it do? In this article, we’ll take you through the role of L-Theanine and how you can get more of it into your diet. 

So, what is L-Theanine? 

L-Theanine is the most common form of Theanine, a naturally occurring amino acid that can help mind relaxation¹. 

First discovered by Japanese scientists in 1949, L-Theanine is found in green tea. It’s actually one of the components that gives green tea its distinct taste². You can also find it in black tea and certain types of mushrooms. 

H3: L-Theanine vs L-Tyrosine

L-Theanine and L-Tyrosine are two amino acids known for their ability to aid in relaxation. L-Theanine is naturally found in tea leaves and is known for its effects on calming the mind. 

On the other hand, L-Tyrosine is an amino acid produced by the body from another amino acid called phenylalanine. It’s also found in a number of high-protein foods, including chicken, beef, fish, dairy, eggs and nuts³. Like L-Theanine, L-Tyrosine is known to help improve concentration, clarity and focus⁴. 

What does L-Theanine do?

With all that covered, you might be wondering what are the benefits? L-Theanine supports mind relaxation by contributing to several key changes in the brain^{5, 6, 7}. 

Let’s take a closer look.

What does L-Theanine do to the brain?

L-Theanine has a unique function on the brain, contributing to various aspects of mental function well-being. L-Theanine influences certain chemicals in the brain that influence mind relaxation and overall cognitive function. 

L-Theanine impacts GABA, short for Gamma-Aminobutyric Acid, an inhibitory neurotransmitter that helps reduce nerve cell activity. By increasing levels of GABA in the brain, it signals to your body that it’s time to relax, which can help alleviate feelings of stress and help you enjoy a more restful, longer sleep⁸. At the same time, L-Theanine boosts dopamine and serotonin levels, enhancing mood, emotional stability, motivation and cognitive function⁹.

To dive a little deeper, L-Theanine enhances the production of alpha brain waves, which are associated with a state of relaxed alertness¹⁰.  This brain wave pattern is typically observed during meditation¹¹ and has been linked to increased creativity and focus while maintaining a state of calmness and relaxation.

This combination of increased alpha brain activity and neurotransmitter levels helps with cognitive function¹².

Is L-Theanine a nootropic?

Thanks to its impact on mental function and cognitive performance, L-Theanine is considered a nootropic. Nootropics are substances that can enhance cognitive function in healthy individuals. L-Theanine is typically used for its cognitive-enhancing properties, including increased relaxation and improved cognitive function^{13, 14}. 

How to get more L-Theanine into your diet

You can boost your daily intake of L-Theanine through diet and supplementation. As one of the richest natural sources of L-Theanine, drinking green tea can help boost your daily intake. Alternatively, you may like to consider taking an L-Theanine supplement.

Is it ok to take L-Theanine daily?

L-Theanine is generally considered okay to take daily to help with mind relaxation and cognitive performance^{15, 16}. 

The best time to take L-Theanine often depends on the effects you’re trying to benefit from. If you’re hoping to enhance mental alertness and cognitive function, it’s often recommended to take an L-Theanine supplement when you need the extra boost to help you power through the situation. However, if you’re looking to calm the mind, it may help to take an L-Theanine supplement in the evening.

But remember, be sure to consult with your healthcare professional before making changes to your diet, nutritional intake or introducing a new supplement to your daily routine.

Want to learn more about supplements and brain health? Check out the Swisse Wellness Hub for more information on mindfulness, nutrition and more.  

Resources:

1. Everett JM, Gunathilake D, Dufficy L, Roach P, Thomas J, Upton D, et al. Theanine consumption, stress and anxiety in human clinical trials: A systematic review. Journal of Nutrition & Intermediary Metabolism. 2016 Jun;4:41–2.
2. Ashihara H. Occurrence, Biosynthesis and Metabolism of Theanine (γ-Glutamyl-L-ethylamide) in Plants: A Comprehensive Review. Natural Product Communications [Internet]. 2015 May;10(5):1934578X1501000. Available from: https://doi.org/10.1177%2F1934578X1501000525
3. Kühn, S., Düzel, S., Colzato, L., Norman, K., Gallinat, J., Brandmaier, A. M., Lindenberger, U., & Widaman, K. F. (2019). Food for thought: association between dietary tyrosine and cognitive performance in younger and older adults. Psychological research, 83(6), 1097–1106. https://doi.org/10.1007/s00426-017-0957-4
4. Hase, A., Jung, S. E., & aan het Rot, M. (2015). Behavioral and cognitive effects of tyrosine intake in healthy human adults. Pharmacology, biochemistry, and behavior, 133, 1–6. https://doi.org/10.1016/j.pbb.2015.03.008 
5. Evans, M., McDonald, A. C., Xiong, L., Crowley, D. C., & Guthrie, N. (2021). A Randomized, Triple-Blind, Placebo-Controlled, Crossover Study to Investigate the Efficacy of a Single Dose of AlphaWave® L-Theanine on Stress in a Healthy Adult Population. Neurology and therapy, 10(2), 1061–1078. https://doi.org/10.1007/s40120-021-00284-x
6. Dassanayake TL, Wijesundara D, Kahathuduwa CN, Weerasinghe VS. Dose-response effect of L-theanine on psychomotor speed, sustained attention, and inhibitory control: a double-blind, placebo-controlled, crossover study. Nutr Neurosci. 2023 Nov;26(11):1138-1146. doi: 10.1080/1028415X.2022.2136884. Epub 2022 Oct 20. PMID: 36263942.
   
7. Hidese, S., Ogawa, S., Ota, M., Ishida, I., Yasukawa, Z., Ozeki, M., & Kunugi, H. (2019). Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial. Nutrients, 11(10), 2362. https://doi.org/10.3390/nu11102362
8. Kim S, Jo K, Hong KB, Han SH, Suh HJ. GABA and l-theanine mixture decreases sleep latency and improves NREM sleep. Pharmaceutical Biology. 2019 Jan 1;57(1):64–72.
9. Wang, L., Brennan, M., Li, S., Zhao, H., Lange, K., & Brennan, C. (2022). How does the tea L-theanine buffer stress and anxiety. Food Science and Human Wellness, 11(3), 467–475. https://doi.org/10.1016/j.fshw.2021.12.004
10. Juneja LRCD, Okubo T, Nagato Y, Yokogoshi H. l-Theanine—a unique amino acid of green tea and its relaxation effect in humans. Trends Food Sci Technol. 1999;10:425. doi: 10.1016/S0924-2244(00)00031-5.
11. Dobrakowski P, Blaszkiewicz M, Skalski S. Changes in the Electrical Activity of the Brain in the Alpha and Theta Bands during Prayer and Meditation. International Journal of Environmental Research and Public Health. 2020 Dec 21;17(24):9567.
12. 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. https://doi.org/10.1007/s00213-015-3895-0
13. Baba Y, Inagaki S, Nakagawa S, Kaneko T, Kobayashi M, Takihara T. Effects of l-Theanine on Cognitive Function in Middle-Aged and Older Subjects: A Randomized Placebo-Controlled Study. Journal of Medicinal Food. 2021 Apr 1;24(4):333–41.
    
14. Hidese, S., Ogawa, S., Ota, M., Ishida, I., Yasukawa, Z., Ozeki, M., & Kunugi, H. (2019). Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial. Nutrients, 11(10), 2362. https://doi.org/10.3390/nu11102362
15. L-Theanine for Sleep [Internet]. Sleep Foundation. 2022. Available from: https://www.sleepfoundation.org/sleep-aids/l-theanine-for-sleep
16. Baba Y, Inagaki S, Nakagawa S, Kaneko T, Kobayashi M, Takihara T. Effects of l-Theanine on Cognitive Function in Middle-Aged and Older Subjects: A Randomized Placebo-Controlled Study. Journal of Medicinal Food. 2021 Apr 1;24(4):333–41.