The Mental Health Benefits of L-Theanine for Anxiety, Depression, and More

Theanine is a low-side-effect supplement that may help lift your mood, relieve stress, reduce anxiety, protect your brain cells, and more. 

Theanine is an amino acid but it isn't found in protein sources like many other amino acids. It's a non-protein amino acid most commonly found in tea.

In a 2019 article for Elle magazine, Taylor Swift gave theanine a shout-out for the benefits she has gained from taking it as a supplement: (1)

"Vitamins make me feel so much better! I take L-theanine, which is a natural supplement to help with stress and anxiety. I also take magnesium for muscle health and energy." —Taylor Swift

What's In This Post

Disclaimer: The information in this article should not be taken as medical advice. It is always advisable to check with your personal medical professionals for individualized advice. 

Why the “L” in L-Theanine?

If you’ve looked at taking amino acids as supplements you may have noticed that most have an L in front of the amino acid name (like L-theanine).

Some amino acids occur in two forms that are mirror images of each other: L and D.

Only the L-forms can be used by your body’s cells. 

Whenever I mention theanine throughout this article, I am referring to the L-form. 

Mental Health Benefits of L-Theanine

Theanine has been demonstrated to have many positive effects on physical and mental health. 

Research results show that L-theanine may: (2-20)

1. lift depression

2. increase stress resilience

3. reduce anxiety

4. induce relaxation

5. assist sleep (particularly if anxious thoughts are keeping you awake) without causing a drowsy sedative effect

6. improve learning and memory

7. protect brain cells (neuroprotection)

8. reduce nicotine dependence

What Does L-Theanine Do?

Theanine helps you mentally through several different ways it positively impacts you physically.

Theanine appears to:

1. be anti-oxidative

2. be anti-inflammatory

3. help feel-good neurotransmitters

4. inhibit an anxiety-provoking neurotransmitter

5. relax brain waves

6. NOT create drowsiness (even though it helps with sleep)

1. Theanine is anti-oxidative

Anything that counters oxidation has the potential to protect brain cells. 

Several things make your brain particularly vulnerable to oxidative stress, including brain cells’ high fat content and the fact that your brain is one of the most active organs in your body. (21)

All that activity creates a large amount of free radical reaction leftovers. Stress potentially increases your brain’s free radical load even further. (22)

Over the last decade, more and more research is pointing toward unchecked oxidation (AKA oxidative stress) as a potential contributor to anxiety, depression, and other mental health issues. (23)

Mental/emotional stress can lead to oxidative stress and oxidative stress can contribute to mental/emotional stress. It’s a vicious circle that you can help break with the care and feeding of your brain with antioxidants. 

2. Theanine is anti-inflammatory

Like the connection between oxidation and mental health, inflammation has recently received a lot of attention for its newly appreciated status as a contributor to mental health issues. (24)

Published in 2012, the 88^th volume of the book series Advances in Protein Chemistry and Structural Biology, containing chapters by academics considered experts in their fields, is subtitled Inflammation in Neuropsychiatric Disorders. The title itself seems to back up the idea that there is growing acceptance of the connection between your mental state and the amount of inflammation in your body. Advances in Protein Chemistry and Structural Biology: Inflammation in Neuropsychiatric Disorders includes chapters about depression, schizophrenia, Parkinson’s, and anxiety. (25)

3. & 4. Theanine helps neurotransmitters

Theanine is able to cross the blood-brain barrier and has been shown to impact your neurotransmitters in several ways that can help you deal with stress, reduce anxiety, and relieve depression including: (26-27)

• increase the feel-good and relaxing neurotransmitters GABA, serotonin, and dopamine, and

• reduce the impact of the excitatory neurotransmitter glutamate by blocking glutamate receptors.

 5. Theanine relaxes brain waves

Several research projects, such as a 2016 study in the Netherlands, have demonstrated that alpha brain wave levels (typical of a relaxed state) increase after ingesting a theanine supplement. (27)

 6. Theanine does NOT create drowsiness

Importantly, while theanine is relaxing, it does not cause drowsiness or act as a sedative.

In a 2007 article in the Psychiatric Times journal, Dr. James Lake compares L-theanine to anti-anxiety meds: 

"Unlike benzodiazepines and other conventional anti-anxiety treatments, L-theanine does not result in increased drowsiness, slowed reflexes, or impaired concentration. There is no risk of tolerance or dependence developing, and there have been no reports of serious adverse effects or interactions with other natural products or conventional drugs."

And there is this statement by Russ Mason, MS in a 2001 Alternative & Complimentary Therapies article: 

"People who are in stressful situations—whether they are environmental, personal, or medical in origin—can mitigate the harmful effects of stress significantly with L-theanine, without becoming sedated in the process."

How Much L-Theanine is in Green Tea?

The predominant food source for theanine is tea. (Some rarely-eaten mushrooms have trace amounts.)

Recent studies give different and conflicting results for the theanine content of various teas.

One found more theanine in green tea compared to black tea. (28)

Another study found the opposite. (29)

A third found both to be about the same. (30)

Averaging the results from these studies, the approximate amount of theanine is 4 to 30 mg per cup of brewed tea.

For comparison, the 2016 Dutch study referenced above in the Theanine relaxes brainwaves section used 200 mg theanine supplement for subjects. (31)

L-Theanine in Matcha Tea

Matcha is a special tea made by dissolving ground green tea leaves grown in shade.

It potentially contains higher amounts of both caffeine and theanine compared to other teas. 

Japanese researchers who examined matcha tea samples for their relative caffeine and theanine levels concluded that 32 out of the 76 brands they purchased in Japan met their criteria for possibly assisting with stress resilience, but only 1 of the brands that they purchased "overseas" met their criteria. (32)

L-Theanine Dosage

In Prescription for Natural Cures, doctors Mark Stengler, James Balch, and Robin Young Balch recommend:

• 200 to 250 mg of L-theanine twice a day for anxiety (33)
• 200 to 500 mg in one dose a half hour before bed for insomnia (34)

In The Psychiatric Times journal (Nov 2007), Dr. James Lake makes the following suggestions [Note: L-theanine taken in chewable forms may act faster than the capsule forms he is referring to]: 

"A calming effect is usually noted within 30 to 40 minutes after L-theanine is taken at doses of 50 to 200 mg, and typically lasts 8 to 10 hours. Moderate anxiety symptoms often improve in patients taking 200 mg once or twice daily. More severe anxiety symptoms may require dosages of 600 to 800 mg/d, taken in divided doses of 100 to 200 mg."

L-Theanine Supplements

L-theanine is readily available as a supplement in powder, capsule, softgel, chewable, gummy, or liquid form.

While L-theanine, not D-theanine, is the target anti-anxiety nutrient, many supplements contain a combination of the D and L forms. Look for supplements that only contain the L-form.

Suntheanine is a patented type of theanine that is entirely L-theanine. Many different companies have Suntheanine-based products (e.g., Doctor’s Best, Sport’s Research, and Integrative Therapeutics).

Here's a couple of sources for L-theanine. (Links are placed for your convenience. I may receive a small commission for purchases through links in this article, but it does not impact your cost or my decision to place the link.)

NOW Supplements, L-Theanine 100 mg with Inositol and Taurine

This chewable has L-theanine plus a couple of additional supplements (inositol and taurine) that have anti-anxiety properties. One of my clients swears by this brand for panic attacks. 

EZ Melts 200mg melt-in-your-mouth tablets

This has double the dose of the NOW chewables but doesn't have the additional anti-anxiety inositol or taurine.

Sports Reseach Suntheanine 200mg capsules

L-Theanine Side Effects

Theanine reduces blood pressure so it should be avoided for people with low blood pressure. 

It is always advisable to consult with your personal medical professionals before taking supplements. People on pharmaceutical medications, as well as pregnant and breastfeeding women, should be particularly cautious. 

L-Theanine Benefits, Mechanisms of Action, Dosage, and Research References

(1) 30 things I learned before turning 30. (2019, March 6). ELLE. 

(2) Williams, J. L., Everett, et.al. (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 (Dordrecht, Netherlands), 75(1), 12–23. https://doi.org/10.1007/s11130-019-00771-5

(3)  Lopes Sakamoto, et. al. (2019). Psychotropic effects of L-theanine and its clinical properties: From the management of anxiety and stress to a potential use in schizophrenia. Pharmacological research, 147, 104395. https://doi.org/10.1016/j.phrs.2019.104395

(4) Nathan, P. J., Lu, K., Gray, M., & Oliver, C. (2006). The neuropharmacology of L-theanine(N-ethyl-L-glutamine): a possible neuroprotective and cognitive enhancing agent. Journal of herbal pharmacotherapy, 6(2), 21–30.

(5) Rao, T. P., Ozeki, M., & Juneja, L. R. (2015). In Search of a Safe Natural Sleep Aid. Journal of the American College of Nutrition, 34(5), 436–447. https://doi.org/10.1080/07315724.2014.926153

(6) Yin, C., et. al. (2011). Antidepressant-like effects of L-theanine in the forced swim and tail suspension tests in mice. Phytotherapy research : PTR, 25(11), 1636–1639. https://doi.org/10.1002/ptr.3456

(7) Hidese, S., et. al. (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) Kahathuduwa, et. al. (2017). Acute effects of theanine, caffeine and theanine-caffeine combination on attention. Nutritional neuroscience, 20(6), 369-377.  https://doi.org/10.1080/1028415X.2016.1144845

(9) Lyon, M. R., Kapoor, M. P., & Juneja, L. R. (2011). The effects of L-theanine (Suntheanine®) on objective sleep quality in boys with attention deficit hyperactivity disorder (ADHD): a randomized, double-blind, placebo-controlled clinical trial. Alternative medicine review : a journal of clinical therapeutic, 16(4), 348–354. 

(10) Yamada, T., et. al. (2008). Effects of theanine, a unique amino acid in tea leaves, on memory in a rat behavioral test. Bioscience, biotechnology, and biochemistry, 72(5), 1356–1359. https://doi.org/10.1271/bbb.70669

(11) Lardner, A. L. (2014). Neurobiological effects of the green tea constituent theanine and its potential role in the treatment of psychiatric and neurodegenerative disorders. Nutritional Neuroscience, 17(4), 145–155. https://doi.org/10.1179/1476830513Y.0000000079

(12) Saeed, M., Naveed, et. al. (2017). Green tea (Camellia sinensis) and l-theanine: Medicinal values and beneficial applications in humans—A comprehensive review. Biomedicine & Pharmacotherapy, 95, 1260–1275. https://doi.org/10.1016/j.biopha.2017.09.024

(13) Higashiyama, Akiko, et. al. “Effects of l-Theanine on Attention and Reaction Time Response.” Journal of Functional Foods 3, no. 3 (2011): 171–78. https://doi.org/10.1016/j.jff.2011.03.009. 

(14)  Hwang YP, Jin SW, Choi JH, et al. Inhibitory effects of l-theanine on airway inflammation in ovalbumin-induced allergic asthma. Food Chem Toxicol. 2017;99:162‐169. doi:10.1016/j.fct.2016.11.032

(15) Kimura, Kenta, Makoto Ozeki, Lekh Raj Juneja, and Hideki Ohira. "L-Theanine reduces psychological and physiological stress responses." Biological Psychology 74.1 (2007): 39-45.

(16) 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. http://doi.org/10.1186/1880-6805-31-28

(17) Unno, K., 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. https://doi.org/10.1016/j.pbb.2013.09.004

(18) Unno, K., Iguchi, K., Tanida, N., Fujitani, K., Takamori, N., Yamamoto, H., . . . Hoshino, M. (2012). Ingestion of theanine, an amino acid in tea, suppresses psychosocial stress in mice. Experimental Physiology,98(1), 290-303. doi:10.1113/expphysiol.2012.065532

(19)  Chandrasekhar B. V. S, Elango P, Maheswari S. U, Rajukumar D. A Focus on the Effect of L-Theanine on Improving Depression and Cognition in C57BL/J Male Mice Subjected for Chronic Stress Induced Neuroinflammation. Biomed Pharmacol J 2017;10(2). https://dx.doi.org/10.13005/bpj/1199

(20) Di, X., Yan, J., Zhao, Y., Chang, Y., & Zhao, B. (2012). L-theanine inhibits nicotine-induced dependence via regulation of the nicotine acetylcholine receptor-dopamine reward pathway. Science China. Life sciences, 55(12), 1064–1074  https://pubmed.ncbi.nlm.nih.gov/23233221/ 

(21). Felicity Ng et al., “Oxidative Stress in Psychiatric Disorders: Evidence Base and Therapeutic Implications,” The International Journal of Neuropsychopharmacology 11, no. 06 (2008), https://doi.org/10.1017/s1461145707008401.

(22). Giancarlo Lucca et al., “Increased Oxidative Stress in Submitochondrial Particles into the Brain of Rats Submitted to the Chronic Mild Stress Paradigm,” Journal of Psychiatric Research 43, no. 9 (2009): 864–869, https://doi.org/10.1016/j.jpsychires.2008.11.002.

(23) Salim S. (2014). Oxidative stress and psychological disorders. Current neuropharmacology, 12(2), 140–147. https://doi.org/10.2174/1570159X11666131120230309  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3964745/

(24) Martone, Gerald, The inflammation hypothesis and mental illness. J Clin Psychiatr Neurosci Vol.2 No.1 June 2019, 3-12. https://www.pulsus.com/scholarly-articles/the-inflammation-hypothesis-and-mental-illness.pdf

(25). S. Salim, G. Chugh, and M. Asghar, Advances in Protein Chemistry and Structural Biology: Inflammation in Neuropsychiatric Disorders, ed. R. Donev (Oxford: Academic, 2012).

(26) Bryan, Janet, “Psychological Effects of Dietary Components of Tea: Caffeine and L-Theanine,” Nutrition Reviews 66, no. 2 (2008): 82–90, https://doi.org/10.1111/j.1753-4887.2007.00011.x.

(27) White,  David, et al., “Anti-Stress, Behavioural and Magnetoencephalography Effects of an L-Theanine-Based Nutrient Drink: A Randomised, Double-Blind, Placebo-Controlled, Crossover Trial,” Nutrients 8, no. 1 (2016): 53, https://doi.org/10.3390/nu8010053.

(28). Emma K. Keenan et al., “How Much Theanine in a Cup of Tea? Effects of Tea Type and Method of Preparation,” Food Chemistry 125, no. 2 (2011): 588–94, https://doi.org/10.1016/j.foodchem.2010.08.071.

(29). Guoqiang Chen et al., “Rapid and Selective Quantification of L-Theanine in Ready-to-Drink Teas from Chinese Market Using SPE and UPLC-UV,” Food Chemistry 135, no.2 (2012): 402–07, https://doi.org/10.1016/j.foodchem.2012.04.084.

(30). Klára Boros, Dezső Csupor, and Nikoletta Jedlinszki, “Theanine and Caffeine Content of Infusions Prepared from Commercial Tea Samples,” Pharmacognosy Magazine 12, no. 45 (2016): 75–79, https://doi.org/10.4103/0973-1296.176061.

(31). White et al., “Anti-Stress, Behavioural and Magnetoencephalography Effects.”

(32). Unno, Keiko, et. al. "Stress-Reducing Function of Matcha Green Tea in Animal Experiments and Clinical Trials." Nutrients 10, no. 10 (2018), 1468. doi:10.3390/nu10101468.

(33). James F. Balch, Mark Stengler, and Robin Young Balch, Prescription for Natural Cures: A Self-Care Guide for Treating Health Problems with Natural Remedies Including Diet, Nutrition, Supplements, and Other Holistic Methods, Revised Edition (Nashville, TN: Turner Publishing Company, 2016), 53.

(34). Balch, Stengler, and Young Balch, Prescription for Natural Cures, 412.

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