Calm Down with L-Theanine

In today’s hectic world, many of us need to find safe ways to reduce stress and calm down.

Stress can severely harm quality of life. Chronic stress boosts risk of physical and mental problems,1 and can impact an individual’s immune function.²

L-theanine is an amino acid found in green tea. It has been recognized for its ability to safely reduce anxiety, calm the mind and produce a state of relaxation³ without drowsiness.^3-5

Clinical studies confirm that L-theanine has relaxing properties that have stress-relieving effects on the body.^6-9

One study published in 2024 showed that L-theanine lowered perceived stress by nearly 18%, enhanced sleep quality, and provided a sustained improvement in cognitive attention.⁷

A Serious Health Risk

Stress is the body’s way of helping you deal with occasional, serious risks to life and health. After a perceived danger has passed, your stress hormones, heart rate, and blood pressure levels are supposed to return to normal.¹⁰

But when life throws constant stressors at you, that fight-or-flight reaction can stay turned on.¹⁰

Excessive exposure to stress hormones such as cortisol and the long-term activation of the stress response system can put your health in danger. This chronic stress increases the risk of: ^1,10

• Heart disease, heart attack, high blood pressure, and stroke,¹⁰
• Musculoskeletal problems,¹⁰
• Depression,¹⁰
• Digestive issues,¹⁰
• Headaches, muscle tension, and pain,¹⁰
• Chronic fatigue, ¹⁰
• Hormonal imbalance/menstrual irregularities,¹⁰
• Dysregulation of the immune system,^1,10
• Weight gain,¹⁰ and
• Memory and cognition problems.¹

Researchers have looked for healthy ways to promote non-sedative alert relaxation.

Despite containing caffeine, green tea has traditionally been associated with producing a calming effect.¹¹

In 1949, scientists identified the specific compound in green tea leaves associated with these relaxing, anti-stress effects: L-theanine.¹¹

How L-Theanine Blocks Stress

L-theanine is a water-soluble amino acid⁷ that has the ability to cross the blood-brain barrier.⁵

L-theanine works to reduce stress by the following mechanisms:

• Preclinical evidence suggests that it modulates activity of the excitatory neurotransmitter glutamate.¹²
• In preclinical studies L-theanine is found to be associated with stimulating the production of the relaxing neurotransmitter GABA (our main inhibitory neurotransmitter) as well as enhancing dopamine release.⁵ Levels of GABA are associated with sleep, and reduced feelings of stress and anxiety. Dopamine is associated with learning and mood.¹³
• In human studies L-theanine has been shown to increase alpha wave activity in the brain, especially in individuals with moderate to high anxiety levels.^6,7,14 Alpha waves are associated with a relaxed but alert mental state.¹⁵

In 1964, after Japanese researchers conducted numerous clinical trials demonstrating that L-theanine is both safe and effective, Japanese authorities declared it to be completely safe and approved adding it to foods.16

Since then, multiple clinical studies have shown that L-theanine effectively reduces stress.^3,17-19

Clinically Validated

In one unpublished study, scientists enlisted healthy subjects, aged 21 to 47, who were considered not particularly stressed. The study involved initial screening and an experimental visit lasting two hours.⁹

During this experimental visit one group took a placebo, and the other took 200 mg of L-theanine.

Prior to taking the doses participants were tested for alpha brain waves (by electroencephalography, or EEG) seven times over a 120-minute period and received a stress test. Ninety minutes after receiving the dose, two further stress tests were administered, and heart rate was measured three times.⁹

The L-theanine group had:⁹

• Increased alpha brain wave activity, indicating increased relaxed wakefulness (while the placebo group’s activity was unchanged),
• Significantly less fatigue than the placebo group,
• Decreased tension and anxiety, and
• Lower heart rates, a further sign of stress reduction.

This shows L-theanine is effective in helping to reduce heart rate and increase relaxation, and has the potential to relieve stress.⁹

In a triple blind, placebo-controlled, crossover study, individuals aged 19 to 60 were evaluated who were moderately stressed.⁶

At screening, participants were randomized to the L-theanine or placebo group and were given instructions and kits to collect salivary cortisol levels. Subjects were given either a placebo or 200 mg of L-theanine, as well as an arithmetic test to induce mental stress before and after they received the dose.

Alpha brain wave activity, salivary cortisol levels, and vital signs were recorded before and after participants took the arithmetic test. There was a seven-day washout period between the L-theanine test and placebo test. Participants returned for the crossover period and all assessments from the first study period were repeated.

All participants experienced stress during the test, as evidenced by increases in heart rate, blood pressure, and self-reported stress and anxiety. But three hours later, those who had taken L-theanine had greater alpha wave activity compared to the placebo, showing a higher level of alert relaxation without drowsiness.

L-theanine also resulted in greater decreases in salivary cortisol levels, compared to placebo, further indicating increased relaxation and calm.⁶

These studies show how L-theanine can reduce the nervous system’s stress reaction, which can yield benefits for body and mind.

Recent Human Trial

A clinical study published in 2024 enrolled healthy but moderately stressed subjects. But this time, treatments continued over a 28-day period.⁷

Subjects ranging from 18 to 65 years were randomly given either a placebo or 400 mg of L-theanine daily, taken as 200 mg in the morning and at night.

Participants were asked to maintain their normal lifestyle, avoid high caffeine consumption (no more than two cups of coffee a day), and refrain from vigorous exercise within 24 hours of testing days.

Tests and other evaluations were done at baseline, day 14, and day 28. On day 28, the L-theanine group had:7

• About 18% lower levels of perceived stress,
• Improved sleep quality, and
• Greater cognitive attention.

The significantly lower levels of self-perceived stress corresponded with a decrease in morning salivary cortisol.

This shows that L-theanine can reduce general stress over an extended period in people who experience stress on a regular basis, and this may improve the quality of life.⁷

Green tea has only about 8 mg of L-theanine per cup.²⁰ Studies on L-theanine’s anti-stress effects usually use a 200 mg dose, taken once or twice daily.^6,7

Summary

Stress contributes to reduced quality of life and greater risk for chronic disorders and impaired immune system function.

L-theanine, an amino acid found in green tea, has been clinically shown to reduce stress and enhance relaxation while maintaining alertness.

In human trials, L-theanine reduced signs of stress after just a single 200 mg dose. It also improved sleep, relaxation, and cognitive attention after 28 days of daily use without serious adverse effects. •

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

References

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. Seiler A, Fagundes CP, Christian LM. The Impact of Everyday Stressors on the Immune System and Health. Stress Challenges and Immunity in Space 2020:71-92.
3. 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.
4. Rao TP, Ozeki M, Juneja LR. In Search of a Safe Natural Sleep Aid. J Am Coll Nutr. 2015;34(5):436-47.
5. Wang L, Brennan M, Li S, et al. How does the tea L-theanine buffer stress and anxiety. Food Science and Human Wellness. 2022 2022/05/01/;11(3):467-75.
6. 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.
7. Moulin M, Crowley DC, Xiong L, et al. Safety and Efficacy of AlphaWave® l-Theanine Supplementation for 28 Days in Healthy Adults with Moderate Stress: A Randomized, Double-Blind, Placebo-Controlled Trial. Neurology and Therapy. 2024 Aug;13(4):1135-53.
8. Hidese S, Ogawa S, Ota M, et al. Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial. Nutrients. 2019 Oct 3;11(10).
9. 9. Campbell A, Sixtus R. The Effects Of The Alphawave® L-Theanine Study Product On Relaxation, Clarity And Cognitive Function. 2016. Available at: https://www.apa.org/topics/stress/body. Accessed October 15, 2024.
10. Saeed M, Naveed M, Arif M, et al. Green tea (Camellia sinensis) and l-theanine: Medicinal values and beneficial applications in humans-A comprehensive review. Biomed Pharmacother. 2017 Nov;95:1260-75.
11. Unno K, Taguchi K, Konishi T, et al. Theanine, a Tea-Leaf-Specific Amino Acid, Alleviates Stress through Modulation of Npas4 Expression in Group-Housed Older Mice. Int J Mol Sci. 2023 Feb 16;24(4).
12. Hussain S, Muhammad I, Esha N, et al. A Comprehensive Review on Neurotransmitters, Its Biological Importance and Methods of Analysis. The Journal of Microbiology and Molecular Genetics. 2023 12/01;4(3):11-41.
13. 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).
14. Xavier G, Su Ting A, Fauzan N. Exploratory study of brain waves and corresponding brain regions of fatigue on-call doctors using quantitative electroencephalogram. J Occup Health. 2020 Jan;62(1):e12121.
15. Lu Y, Zhang J, Wan X, et al. Intestinal transport of pure theanine and theanine in green tea extract: Green tea components inhibit theanine absorption and promote theanine excretion. Food Chemistry. 2011 2011/03/15/;125(2):277-81.
16. Mason R. 200 mg of Zen: L-Theanine Boosts Alpha Waves, Promotes Alert Relaxation. Alternative and Complementary Therapies. 2001 04/01;7(2):91-5.
17. 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.
18. 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.
19. Wang Q, Zheng Y, Ho C-T, et al. L-theanine as a promising agent on brain health-promoting foods – A review. Journal of Food Bioactives. 2021 03/31;13(0).