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l theanine side effectsl theanine benefits l theanine dosage what does l theanine do when to take l theanine is l theanine safe ? How does l theanine work

Your ultimate guide to l-theanine: benefits, side effects & dosage


In recent years green tea has attracted a lot of attention. Some of it leads back to its favourable taste, however, the relaxation-boosting ingredient called l-theanine is the real reason behind it. L-theanine benefits health in many crucial ways of immense importance in today’s society. Discover what l-theanine is and how does l-theanine work

L-theanine: an introduction 

L-theanine is a compound first found in the tea plant in 1949[1,2]. It contributes to the unique taste similar to the savoury taste sensation known as umami[1,2]. Enough l-theanine helps you relax while still keeping you alert[3,4]. L-theanine increases the relaxation chemical GABA and brain waves linked to focus known as alpha waves[5,6,7]. Studies have shown that l-theanine benefits stress and anxiety levels[8,9]. So, what does l-theanine do exactly? A literature review of 9 studies with 270 participants presented the evidence on the relaxing benefits of l-theanine while also addressing the question of how safe it is[1]. 

Destress with l-theanine

Imagine you’re giving a presentation at work. You feel like you are prepared enough but unsure how others will feel about it. An Australian literature review team examined 9 studies assessing the effects of l-theanine on participants[8]. They concluded that l-theanine assists in reducing stress in people exposed to stressful conditions. So, taking a capsule of theanine before your presentation would help you calm down while keeping you collected and alert[1,5,6,7]. A study of 20 participants also showed that levels of the body’s stress indicators dropped after l-theanine intake[10]. 

L-theanine as an anxiety reliever?

Two in-depth literature reviews examined human studies and the connection between l-theanine and anxiety, and found that:

  • the anti-anxiety effects of l-theanine may vary depending on the intensity of the anxiety[9],
  • l-theanine alleviated the initial anxiety[9], and
  • l-theanine reduced acute anxiety which happens in the moment of a stressful situation[1],
  • there is insufficient evidence to suggest l-theanine assists in the reduction of stress levels in people with chronic conditions for example a generalised anxiety disorder or in people who are generally just more of an anxious person, also called trait anxiety[1].

While there is some promising research into l-theanine and anxiety, more extensive studies would be beneficial to make any concrete conclusions. At present, the NHS does not recommend l-theanine as a treatment for anxiety. If you’re dealing with anxiety, read here about your options or talk to your GP. 

Safe and natural relaxant 

So, is l-theanine safe? In short, yes it is. The above-mentioned literature review of 9 studies has concluded that l-theanine side effects are uncommon and that it appears taking 400mg of l-theanine daily for 8 weeks is perfectly safe[1]. L-theanine also has a GRAS status rewarded by the U.S. Food & Drug Administration meaning it’s generally recognized as safe for extended periods. Getting your daily intake of l-theanine by drinking tea is possible, though it may come with possible side effects, including blocking other compounds like vitamin B1[1]. Therefore, l-theanine supplementation can is a safer choice, however, it is vital to opt for a high-quality supplement. brain feed’s capsules contain 250mg of natural l-theanine extracted from green tea found in the mountainous region in South Central China. Each capsule contains the same amount of l-theanine found in 15-20 cups of green tea. Get 15% off your first order with the code ‘NEW15’. 

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When to take l-theanine & dosage

For l-theanine to be as effective as it can it’s important to follow the science behind it. Multiple studies have shown that a dose between 200mg - 400mg per day helps you feel more relaxed[1]. L-theanine supplements should be taken with a glass of water. Depending on the supplement type and dosage, you should only take as many as possible to reach the recommended daily intake. 

Try this natural and safe relaxant if you want to keep calm and collected in stressful situations. 



[1] Williams, J. L., Everett, J. M., D’Cunha, N. M., Sergi, D., Georgousopoulou, E. N., Keegan, R. J., McKune, A. J., Mellor, D. D., Anstice, N., & Naumovski, N. (2020). The Effects of Green Tea Amino Acid L-Theanine Consumption on the Ability to Manage Stress and Anxiety Levels: A Systematic Review. Plant Foods for Human Nutrition, 75(1), 12–23. 

[2] Vuong, Q. V., Bowyer, M. C., & Roach, P. D. (2011). L-Theanine: Properties, synthesis and isolation from tea. Journal of the Science of Food and Agriculture, 91(11), 1931–1939.

[3] Higashiyama, A., Htay, H. H., Ozeki, M., Juneja, L. R., & Kapoor, M. P. (2011). Effects of l-theanine on attention and reaction time response. Journal of Functional Foods, 3(3), 171–178.

[4]Giles, G. E., Mahoney, C. R., Brunyé, T. T., Taylor, H. A., & Kanarek, R. B. (2017). Caffeine and theanine exert opposite effects on attention under emotional arousal. Canadian Journal of Physiology and Pharmacology, 95(1), 93–100.

[5] Gamma-Aminobutyric Acid (GABA) (2022). Cleveland Clinic.,with%20anxiety%2C%20stress%20and%20fear

[6] Breus, M. J. (2019). 3 Amazing Benefits of GABA. Psychology Today.

[7] 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, 17(S1), 167–168.

[8] Williams, J. L., Everett, J. M., D’Cunha, N. M., Sergi, D., Georgousopoulou, E. N., Keegan, R. J., McKune, A. J., Mellor, D. D., Anstice, N., & Naumovski, N. (2020). The Effects of Green Tea Amino Acid L-Theanine Consumption on the Ability to Manage Stress and Anxiety Levels: A Systematic Review. Plant Foods for Human Nutrition, 75(1), 12–23. 

[9] Wang, L., Brennan, M., Li, S., Zhao, H., Lange, K. W., & Brennan, C. (2022). How does the tea L-theanine buffer stress and anxiety. Food Science and Human Wellness, 11(3), 467–475.

[10] Unno, K., Tanida, N., Ishii, N., Yamamoto, H., Iguchi, K., Hoshino, M., Takeda, A., Ozawa, H., Ohkubo, T., Juneja, L. R., & Yamada, H. (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.

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