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L-Theanine is a calming and focus-enhancing non-dietary amino acid that is not commonly found in food [1, 2]. Instead, it is found primarily in green tea.[3] It is typically used for its relaxing and mildly stimulating effects, but studies also show that it increases mood, improves attention, heightens sleep quality, and has health-promoting properties.[4] [5]


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L-Theanine Reviews



At a Quick Glance


Also Known As


How It Works

Blocks glutamate binding [6]
Improves GABA activity [6]
Boosts serotonin and dopamine [6]
Enhances alpha-brainwaves [7]

Is Used For

Reducing feelings of stress [4]
Cognitive performance [4]
Mood enhancement [4]
Natural sleep aid [4] 

Medical Disclaimer

Not intended to treat, diagnose, or cure any disease or ailment. Please read and fully understand the potential adverse effects before using this product. These statements have not been reviewed by the FDA and are not written by a medical professional. Please consult your doctor before using any supplements, especially if you have any medical conditions.





Benefits and Effects on Humans

Based on Available Scientific Research and Anecdotal Evidence



Used For: Efficacy
Reducing Stress ★★★★★
Cognitive Enhancement ★★★★
Improving Mood ★★★★
Natural sleep aid ★★★★
Neuroprotective ★★★
Synergy with caffeine ★★★★★
Supporting a healthy metabolism ★★★



How to Use

Recommended Serving Size and Application


Serving size

According to clinical research, L-Theanine is usually taken at a serving size of around 100-200 mg, and often combined with Caffeine [1, 2]. Many of the most recent studies on L-Theanine have used servings of 200 mg, twice daily [8]. Our L-Theanine capsules contain 200 mg pure L-Theanine. Powder form L-Theanine from Liftmode comes with a 0.65cc measuring scoop and is guaranteed to be at least 99% pure, with an included certificate of analysis (CoA).



In capsule form: Simply swallow 1-2 capsules with a glass of water.

In powder form:

  1. ‘Solution’ method:
    1. Measure the correct serving size of L-Theanine with a measuring scoop or scale.
    2. Pour into a glass of water.
    3. Stir until fully dissolved (easier with HCl form), and swallow.
    4. If necessary, wash the glass out with more water and swallow any residual undissolved powder.



Evidence-Based Research




1. Summary


L-Theanine (also known as Theanine or 5-N-Ethyl-Glutamine) is a relatively rare phytochemical found in a few species of tea and mushrooms [1]. It is especially associated with Green Tea, where it contributes to some of the tea’s flavor. L-Theanine is a non-dietary amino acid that does not play a role in forming proteins. Instead, it stimulates neurotransmitter activity and in doing so, has effects on the brain and body [2]

L-Theanine is very similar in structure to glutamine and GABA [9, 10]. It is typically thought of as a relaxing agent that produces a state of relaxation without promoting drowsiness [2]. Furthermore, L-Theanine is a powerful, natural stress-reducing agent that may also improve cognitive performance (e.g. attention, focus, and memory) [4]. Although studies have not yet been conclusive in showing that L-Theanine is a natural sleep aid, it may help to promote good sleep quality [4]. This means that it does not necessarily make you fall asleep, but it does help promote healthier, calmer, and deeper sleep.

Interestingly, L-Theanine may be able to alter the perception of taste in a number of plant species where it occurs naturally. More specifically, research points to L-Theanine being able to help reduce sensations of bitterness in foods such as chocolate, zinc, tea, grapefruit, and ginseng due to its ability to promote a 5th taste known as umami [11, 12].

Green tea has been used throughout the world, especially in the East, for thousands of years, and has long been known to have positive effects on human health. Indeed, in 600 A.D., a Chinese writer called Lu Yu wrote a book called the Cha Jing (the Tea Classic), documenting some of the known history of green tea and how the perfect cup should be created. It wasn’t until much more recently that we discovered the chemical constituents of tea and their potential benefits on human health!

L-Theanine is presently being studied for a number of health benefits including stress reduction, improved mood and focus, better sleep quality and a variety of secondary health benefits [1 - 4]. See this excerpt below, from the Memorial Sloan-Kettering Cancer Center’s article:

“[L-theanine] is consumed for its perceived antioxidant and relaxant effects. Several in vitro and animal studies have shown that L-theanine has lipid-lowering, neuroprotective, antiobesity… properties.”[13] 

l-theanine is great for relaxation


2. Chemical Information


Chemically, L-Theanine is the enantiomer of D-Theanine, and it is a member of the glutamine derivatives class of compounds, which refers to compounds that contain glutamine or a derivative. Furthermore, it is an analogue of the amino acid L-Glutamine, and it is ethylated on the amide nitrogen. Similarly, both L-Theanine and L-Glutamine are non-proteinogenic amino acids ( not used to synthesize proteins). L-Theanine is water soluble and moderately acidic [14].



3. Benefits and Effects in Humans


3.1. Helps to Reduce Feelings of Stress & Promotes Relaxation

One of the most important effects of L-Theanine supplements is the ability to help reduce feelings of stress. In a 2004 study, the effects of L-Theanine were compared to those of a commonly prescribed anxiolytic compound, in 16 volunteers. L-Theanine was found to reduce baseline stress levels by promoting a calmer and more relaxed feeling, while the common anxiolytic compound had no effect on baseline stress levels.[15] Stress is often related to mood and thusly, L-Theanine has also been shown to have potent mood-enhancing effects.

L-Theanine has also been directly shown in a number of studies to increase the activity of alphabrainwaves [2]. Enhanced alpha brainwaves are associated with a relaxed mental state, without drowsiness as reported by participants involved in alpha-wave studies.[2] Alpha brainwaves are also known to exert a positive influence on attention and arousal [16].

In a 2007 clinical trial, researchers conducted a double-blind study involving twelve participants who underwent four separate trials, each involving L-Theanine supplementation or a placebo. The participants were also asked to perform a number of arithmetic tasks that were designed to induce stress. The results of the study showed that L-Theanine supplements helped reduce heart rate as well as salivary immunoglobulin A (s-IgA), which is a strong indicator of stress. The researchers suggested that L-Theanine could reduce feelings of stress through the inhibition of cortical neuron excitation [17].


3.2. Helps to Support Enhanced Cognitive Performance

The structure of L-Theanine is highly similar to glutamate - a molecule that is known for the role it plays in memory function [9]. Accordingly, L-theanine is able to penetrate through the blood-brain barrier and has been shown to protect neurons (brain cells) from damage and decay [6]. Similarly, studies have shown that L-Theanine effectively increases brain serotonin, dopamine, and GABA levels [6, 18], all of which are very important neurotransmitters (neurochemicals) involved in the maintenance of mood, rest, and emotions.

Increases in these neurochemicals are associated with improvements in mood, attention, and relaxation. In both the East and the West, it has long been known that drinking tea helps individuals manage stress. Indeed, a number of scientific studies have [19].

There has also been a lot of research regarding the effects of L-Theanine in combination with caffeine, with the results generally showing that the combination boosts both mood and brain power [20]. One double-blind placebo study, which is the most acknowledged type of scientific study, involving 44 young adults and their response to a difficult cognitive task, found that L-Theanine, in combination with caffeine, increased alertness and boosted brain power better than either compound taken alone [19].


3.3. Helps to Improve Sleep Quality

There is evidence that L-Theanine supplements can significantly improve sleep quality. In a 2011 study involving children with attention-deficit/hyperactivity (ADHD) disorder, researchers found that daily supplementation of 400 mg L-Theanine significantly improved sleep quality over a six-week period [8]. Ninety-eight boys aged 8-12 years old who had previously been diagnosed with ADHD, were given L-Theanine or a placebo for 6 weeks. Their sleep quality was monitored for five nights at the start and end of the supplementation period by using wrist actigraphy and a Sleep Questionnaire that was completed by their parents.

A second study that was conducted in Japan, involving 20 healthy adult participants found that taking L-Theanine for seven days was a safe and effective supplement for the improvement of sleep and also for reducing sleep disturbances [21]. In these types of studies, it is important to note that, although sleep quality was improved, two factors relating to sleep were not affected: sleep latency (time taken to fall asleep) and sleep duration.


3.4. Has a Highly Synergistic Relationship with Caffeine

Recently, studies have shown that the combination of L-Theanine and Caffeine is better at boosting accuracy and attention as well as significantly improving cognitive performance than using Caffeine alone [1, 2, 6, 9, 11]. The studies have been replicated using a similar L-Theanine dosage, and have come to the same conclusions.

These results are important and interesting because consuming Caffeine alone is known to increase cognitive performance as well as attention and memory [22]. The addition of L-Theanine, however, seems to greatly improve these well-known Caffeine benefits. For example, a recent study found that adding 250 mg pf L-Theanine to 150 mg of anhydrous Caffeine resulted in an improvement in reaction time and alertness with fewer complaints of caffeine-associated headaches [20].


3.5. Other Health Benefits

First, L-Theanine has been shown to target the negative effects of alcohol on the liver. More specifically, an animal study showed that all ethanol metabolizing enzymes in the liver are regulated by L-Theanine. Accordingly, L-Theanine supplementation is associated with a faster metabolism (breakdown) of alcohol and fewer complications from long-term alcohol consumption [23].

Second, supplementation with moderate to large amounts of L-Theanine increased lifespan of a specific type of worm by around 3.6%, on average, and improved maximal lifespan by up to 4.4% [24]. This helps give credibility to the longevity-enhancing claims that have been made about L-Theanine and green tea, although more studies in humans would be helpful.

Third, research has shown that L-Theanine has anticonvulsant properties at low servings, in opposition to caffeine which can sometimes increase the risk of convulsions [25].

Finally, L-Theanine may help improve vascular blood flow through the increased production of the nitric oxide enzyme (eNOS). Nitric oxide is important for regulating blood flow, and an increase in this compound helps improve blood flow by promoting blood vessel expansion and this supports a healthy circulatory system [26].

l-theanine chemical structure



4. Safety and Toxicity


4.1. Side Effects

Research shows that L-theanine is generally safe when used over short periods of time and is used daily by many people [15, 20, 27]. However, there is not enough data on its use in pregnant women to make a conclusion about safety during pregnancy. Talk to your doctor if you are pregnant or breastfeeding and would like to use L-Theanine supplements.

The studies regarding the various health benefits of L-Theanine that we evaluated for this article repeatedly described L-Theanine as a safe and effective supplement, oftentimes implying that it is a safer, more natural alternative to other harmful compounds [6, 15].

Furthermore, large servings of L-Theanine have not been associated with serious side effects [15, 20, 27]. However, it is not recommended to exceed the suggested serving size. Side effects of larger servings may include nausea, upset stomach, and irritability.[19]

If you are taking any medication, it is highly recommended that you consult your physician before using L-Theanine supplements.




Why Buy from Us?

Our mission is to help improve the quality of your life. We develop, test and distribute science-based, top quality pure supplements and nootropics to support your body and mind. We provide independent third-party testing for all our products, which are always shipped with a Certificate of Analysis (CoA) to ensure the highest quality and purity.

We are a multi-faceted team from around the world, with expertise in a variety of areas including biochemistry, physiology, neuroscience, microbiology, as well as business and marketing. We are well-known for our great customer service and high-quality products, attested to on Trustpilot: as well as Reddit, and have an A+ score from the BBB.



How We Research Our Content

Our content is written using meticulous research methods and claims are backed by links to scientific references, wherever possible. The author and editors of Liftmode's Research Team have strong academic backgrounds in microbiology, physiology, and biochemistry.

Content Updated On: February 15, 2019



Content By:

Written By: Tristan Pelser, B.Sc. in Molecular Biology
Medically Reviewed by: Dr. Karen Vieira, PhD in Biomedical Sciences


Scientific Support and References


[1] Einöther, S. J., & Martens, V. E. (2013). Acute effects of tea consumption on attention and mood. American Journal of Clinical Nutrition, 98(6 Suppl):1700S-1708S. 

[2] Nobre, A.C., Rao, A., & Owen, G.N. (2008). L-theanine, a natural constituent in tea, and its effect on mental state. Asia Pac J Clin Nutr, 17 Suppl 1:167-8.

[3] Cartwright, R. A., Roberts, E. H., & Wood, D. J. (1954). Theanine an amino acid of N-ethyl amide present in tea. J Sci Food Agric, 5:597-599.

[4] Türközü, D., & Şanlier, N. (2015). L-theanine, unique amino acid of tea, and its metabolism, health effects, and safety. Critical Reviews in Food Science and Nutrition, 57(8), 1681-1687. 

[5] Adhikary R, & Mandal V. (2017). L-theanine: A potential multifaceted natural bioactive amide as health supplement. Asian Pac J Trop Biomed, 7(9):842-848.

[6] 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. J Herb Pharmacother, 6(2):21-30.

[7] Ito, K., Nagato, Y., Aoi, N., Juneja, L. R., Kim, M., Yamamoto, T., & Sugimoto, S. (1998). Effects of L-theanine on the release of alpha-brain waves in human volunteers. Nippon Nogeikagaku Kaishi, 72:153-157.

[8] 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. Altern Med Rev, 16(4):348-54.

[9] Yamada, T., Terashima, T., Okubo, T., Juneja, L. R., & Yokogoshi, H. (2005). Effects of theanine, r-glutamylethylamide, on neurotransmitter release and its relationship with glutamic acid neurotransmission. Nutr Neurosci, 8(4):219-26.

[10] Başkan, M. H., & Aydın, M. (2013). Electron paramagnetic resonance studies of gamma-irradiated DL-alanine ethyl ester hydrochloride, L-theanine and L-glutamic acid dimethyl ester hydrochloride. Spectrochim Acta A Mol Biomol Spectrosc, 112:280-2.

[11] Mason, R. (2001). L-Theanine boosts alpha waves, promotes alert relaxation: 200 mg of Zen. Alternative and Complementary Therapies, 7(2):91-95.

[12] Narukawa, M., Morita, K., & Hayashi, Y. (2008). L-theanine elicits an umami taste with inosine 5′-monophosphate. Biosci Biotechnol Biochem, 72(11):3015-7.

[13]  L-Theanine. (2018). Memorial Sloan Kettering Cancer Center. [online]. Available at

[14]  Theanine: Compound Summary for CID 439378. (2018). PubChem: US National Library of Medicince. [online]. Available at

[15] Lu, K., Gray, M.A., Oliver, C., Liley, D.T., Harrison, B.J., Bartholomeusz, C.F., Phan, K.L., & Nathan, P.J. (2004). The acute effects of L-theanine in comparison with alprazolam on anticipatory anxiety in humans. Hum Psychopharmacol, 19(7):457-65.

[16] Pivik, R.T., & Harman, K. (1995). A reconceptualization of EEG alpha activity as an index of arousal during sleep: all alpha activity is not equal. J Sleep Res, 4(3):131-137.

[17] Kimura, K., Ozeki, M., Juneja, L.R., & Ohira, H. (2007). L-Theanine reduces psychological and physiological stress responses. Biol Psychol, 74(1):39-45.

[18] Di, X., Yan, J., Zhao, Y., Zhang, J., Shi, Z., Chang, Y., & Zhao, B. (2010). L-theanine protects the APP (Swedish mutation) transgenic SH-SY5Y cell against glutamate-induced excitotoxicity via inhibition of the NMDA receptor pathway. Neuroscience, 168(3):778-86.

[19] Giesbrecht, T., Rycroft, J.A., Rowson, M.J., De Bruin, E.A. (2010). The combination of L-theanine and caffeine improves cognitive performance and increases subjective alertness, Nutr Neurosci, 13(6):283-90.

[20] Haskell, C.F., Kennedy, D.O., Milne, A.L., Wesnes, K.A., Scholey, A.B. (2008). The effects of L-theanine, caffeine and their combination on cognition and mood. Biol Psychol, 77(2):113-22.

[21] Unno, K., Noda, S., Kawasaki, Y., Yamada, H., Morita, A., Iguchi, K., & Nakamura, Y. (2017). Reduced Stress and Improved Sleep Quality Caused by Green Tea Are Associated with a Reduced Caffeine Content. Nutrients, 19;9(7).

[22] Einöther, S. J., & Giesbrecht, T. (2013). Caffeine as an attention enhancer: reviewing existing assumptions. Psychopharmacology (Berl), 2013;225(2):251-74.

[23] Sadzuka, Y., Inoue, C., Hirooka, S., Sugiyama, T., Umegaki, K., & Sonobe, T. (2005). Effects of theanine on alcohol metabolism and hepatic toxicity. Biol Pharm Bull, 28(9):1702-6.

[24] Zarse, K., Jabin, S., & Ristow, M. (2012). L-Theanine extends lifespan of adult Caenorhabditis elegans. Eur J Nutr, 51(6):765-8.

[25] Choopankareh, S., Vafaee, F., Shafei, M.N., Sadeghnia, H.R., Salarinia, R., Zarepoor, L., Hosseini, M. (2015). Effects of melatonin and theanine administration on pentylenetetrazole-induced seizures and brain tissue oxidative damage in ovariectomized rats. Turk J Med Sci, 45(4):842-9.

[26] Siamwala, J.H., Dias, P.M., Majumder, S., Joshi, M.K., Sinkar, V.P., Banerjee, G., & Chatterjee, S. (2013). L-theanine promotes nitric oxide production in endothelial cells through eNOS phosphorylation. J Nutr Biochem, 24(3):595-605.

[27] Hidese, S., Ota, M., Wakabayashi, C., Noda, T., Ozawa, H., Okubo, T., & Kunugi, H. (2017). Effects of chronic l-theanine administration in patients with major depressive disorder: an open-label study. Acta Neuropsychiatr, 29(2):72-9.