Single Dose L-Theanine Lowers Stress

Using an extended-release formulation allows L-theanine to stay in the body for up to six hours to reduce stress without drowsiness.

By Michael Downey.

Stress makes us feel miserable.

It can have a devastating impact on emotional and physical health.

Chronic stress increases cardiovascular risk, diminishes immune function, impairs cognition, induces gastrointestinal problems, contributes to depression, and more.1

A compound found in green tea can help. This amino acid, named L-theanine, promotes stress relief, calm, and relaxation—without causing drowsiness.2

L-theanine is rapidly absorbed and cleared from the body. This causes some people to take multiple doses throughout the day to achieve sustained levels.

Using an immediate- and extended-release technology, scientists have found a way to allow L-theanine to stay in the body for up to six hours.

One study in moderately stressed adults found that a single dose of this form of L-theanine led to a greater increase in indicators of relaxation compared to placebo.3

Deadly Effects of Chronic Stress

Repeated or unrelenting stress leads to a higher risk for cardiovascular disease, diminished immune function, and damaging inflammation.1,4

One of the most widely recognized health effects of chronic stress is an increased risk of heart disease.

Chronic stress has been shown to impair cardiac5 function and can cause high blood pressure, arrhythmia, and vascular inflammation leading to atherosclerosis and stroke.6

Most anti-stress or anti-anxiety drugs cause sedation and other side effects and can be addictive.7 So, scientists have been investigating plant extracts that may safely reduce stress and anxiety without side effects.

L-Theanine Lowers Stress

Researchers have long been investigating an amino acid called L-theanine that is found primarily in the leaves of green tea. Studies show it is able to cross the blood-brain barrier.2

L-theanine has demonstrated anti-stress effects, including reductions in perceived stress and markers of stress response like blood pressure, heart rate, cortisol, and patterns of brain activity.8

This confirms earlier work that showed subjects taking L-theanine reported significantly less subjective stress than those taking placebo.9

Research has revealed that L-theanine generates a sense of relaxation, with alertness, through at least two mechanisms:10-18

  1. Enhances production of the inhibitory (relaxing) neurotransmitter GABA, or gamma amino butyric acid.
    (GABA then influences levels of dopamine and serotonin that also produce relaxing effects.)
  2. L-theanine increases the brain’s production of alpha brain waves. This creates a state of deep relaxation with mental alertness.

Results of Human Studies

Human trials confirm that L-theanine has relaxing properties that relieve stress.3,19

In one study, pharmacy students undergoing high-stress clinical training who took 200 mg of L-theanine twice daily reported feeling significantly less stress than those who took a placebo.9

Another clinical trial was done with healthy men and women, aged 21 to 47, who were not considered to be particularly stressed before the study.19

Each volunteer was subjected to alpha brain wave testing, which measures wakeful relaxation, and heart rate measurements. Then, a stress test was given and measurements were retaken.

Next, half the group was given 200 mg of L-theanine, and half was given a placebo. The stress test was conducted twice more over the following 90 minutes. The alpha brain wave and heart rate tests were also repeated. Results showed that:19

  • Relaxed wakefulness (measured by alpha brain wave activity) increased with L-theanine but not with the placebo,
  • Tension and anxiety were reduced to a greater degree in the L-theanine group, and
  • Heart rates were lowered by L-theanine, compared to placebo, a further sign of stress reduction.

What you need to know

Stress Relief Without Sedation

  • Stress and anxiety can reduce emotional well-being, increase risk for many diseases, and shorten healthy lifespan.
  • Anti-stress medications are often sedative and can be addictive.
  • Clinical studies show that an amino acid found in green tea, L-theanine, promotes calm and relaxation and safely reduces stress without causing drowsiness.
  • People taking just one dose of 200 mg of L-theanine had reduced physiological indicators of stress.

A randomized, triple-blind, placebo-controlled, crossover study was done on healthy but moderately stressed adults aged 19 to 60 years.3

Study subjects took a single dose of 200 mg of an extended-release form of L-theanine, or placebo. All these volunteers took a mental arithmetic test in order to induce mental stress. There was a seven-day washout period between the L-theanine test and the placebo test.

Alpha brain wave activity, salivary cortisol levels, and vital signs were recorded before and after participants took the arithmetic test.

Increases in heart rate, blood pressure, and self-reported stress and anxiety confirmed that subjects experienced stress during the stressful mental test. However, compared to the placebo, 200 mg of L-theanine led to greater alpha wave activity, indicating a higher level of relaxation without drowsiness, just three hours later.3

The “calming response” in brain activity was further supported by greater decreases in salivary cortisol levels, compared to placebo.

In other words, L-theanine reduced feelings of stress and physical markers of stress in the body.


Stress reduces quality of life and boosts the risk of chronic disorders and premature death.

L-theanine, an amino acid found in green tea, lowers stress and promotes relaxation while maintaining alertness.

Unlike anti-anxiety drugs, L-theanine safely relieves stress without causing drowsiness.

L-theanine is rapidly absorbed, but then rapidly cleared from the body. Using an immediate- and extended-release technology, scientists have found a solution to this, allowing L-theanine to stay in the body for up to six hours.

Human trials have shown that L-theanine reduces signs of stress after just a single 200 mg dose.

If you have any questions on the scientific content of this article, please call a Life Extension Wellness Specialist at 1-866-864-3027.


  1. Yaribeygi H, Panahi Y, Sahraei H, et al. The impact of stress on body function: A review. EXCLI J. 2017;16:1057-72.
  2. Williams JL, Everett JM, D’Cunha NM, et al. The Effects of Green Tea Amino Acid L-Theanine Consumption on the Ability to Manage Stress and Anxiety Levels: a Systematic Review. Plant Foods Hum Nutr. 2020 Mar;75(1):12-23.
  3. Evans M, McDonald AC, Xiong L, et al. A Randomized, Triple-Blind, Placebo-Controlled, Crossover Study to Investigate the Efficacy of a Single Dose of AlphaWave((R)) L-Theanine on Stress in a Healthy Adult Population. Neurol Ther. 2021 Dec;10(2):1061-78.
  4. Available at: Accessed August 15, 2022.
  5. Lampert R, Tuit K, Hong KI, et al. Cumulative stress and autonomic dysregulation in a community sample. Stress. 2016 May;19(3):269-79.
  6. Fioranelli M, Bottaccioli AG, Bottaccioli F, et al. Stress and Inflammation in Coronary Artery Disease: A Review Psychoneuroendocrineimmunology-Based. Front Immunol. 2018;9:2031.
  7. Fluyau D, Revadigar N, Manobianco BE. Challenges of the pharmacological management of benzodiazepine withdrawal, dependence, and discontinuation. Ther Adv Psychopharmacol. 2018 May;8(5):147-68.
  8. Turkozu D, Sanlier N. L-theanine, unique amino acid of tea, and its metabolism, health effects, and safety. Crit Rev Food Sci Nutr. 2017 May 24;57(8):1681-7.
  9. Unno K, Tanida N, Ishii N, et al. Anti-stress effect of theanine on students during pharmacy practice: positive correlation among salivary alpha-amylase activity, trait anxiety and subjective stress. Pharmacol Biochem Behav. 2013 Oct;111:128-35.
  10. Foxe JJ, Snyder AC. The Role of Alpha-Band Brain Oscillations as a Sensory Suppression Mechanism during Selective Attention. Front Psychol. 2011 2011-July-05;2(154):154.
  11. Kobayashi K. Effects of L-theanine on the release of alpha-brain waves in human volunteers. Journal of the Agricultural Chemical Society of Japan. 1998;72(2):153-7.
  12. Nobre AC, Rao A, Owen GN. L-theanine, a natural constituent in tea, and its effect on mental state. Asia Pac J Clin Nutr. 2008;17 Suppl 1:167-8.
  13. Song CH, Jung JH, Oh JS, et al. Effects of theanine on the release of brain alpha waves in adult males. Korean J Nutr. 2003;36(9):918-23.
  14. White DJ, de Klerk S, Woods W, et al. Anti-Stress, Behavioural and Magnetoencephalography Effects of an L-Theanine-Based Nutrient Drink: A Randomised, Double-Blind, Placebo-Controlled, Crossover Trial. Nutrients. 2016 Jan 19;8(1).
  15. Yoto A, Motoki M, Murao S, et al. Effects of L-theanine or caffeine intake on changes in blood pressure under physical and psychological stresses. J Physiol Anthropol. 2012 Oct 29;31:28.
  16. Nathan PJ, Lu K, Gray M, et al. The neuropharmacology of L-theanine(N-ethyl-L-glutamine): a possible neuroprotective and cognitive enhancing agent. J Herb Pharmacother. 2006;6(2):21-30.
  17. Vuong QV, Bowyer MC, Roach PD. L-Theanine: properties, synthesis and isolation from tea. J Sci Food Agric. 2011 Aug 30;91(11):1931-9.
  18. Di X, Yan J, Zhao Y, et al. L-theanine protects the APP (Swedish mutation) transgenic SH-SY5Y cell against glutamate-induced excitotoxicity via inhibition of the NMDA receptor pathway. Neuroscience. 2010 Jul 14;168(3):778-86.
  19. Campbell A, Sixtus R. The Effects Of The Alphawave® L-Theanine Study Product On Relaxation, Clarity And Cognitive Function. 2016.