L-Theanine Summary:

L-Theanine is an amino acid analogue found commonly in the plant that gives us green, black and oolong tea (Camellia sinensis).

In recent years it has shown an abundance of beneficial actions on the brain and vascular systems. It works through several pathways including the dopaminergic pathway, vasodilation including the cerebral arteries, and through a possible mimicing action of glutamic acid.

L-Theanine is easily obtained in pure form online, or through high quality shade grown green tea such as matcha or gyokuro. It combines very well with caffeine, and has been shown to ammeliorate many of the negative side effects of this common stimulant.

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Where Does It Come From?

L-theanine is an amino acid isomer found naturally in plants of the Theaceae family. camellia sinensis primarily. In this species, the L-Theanine content is especially high in shade grown crops like Gyokuro or high quality sencha.

Theaceae Family

Camellia sinensis

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Xerocomus badius

 High-quality Matcha is a great source of L-theanine

High-quality Matcha is a great source of L-theanine


L-Theanine In Tea

A many as 50% of the amino acids in green tea comes in the form of theanine, comprising about 1-2% of the total weight of the dried leaf [3].

There seems to be some research being cited on the internet stating that L-Theanine content is higher in black tea than green tea. There are several problems with this study.

For starters, the study was done using tea bags, which are notoriously poor in quality, and not a good representation of the health benefits of tea in general. Additionally, the methods section of this paper offers poor information on the source and style of the tea, which is important to consider based on the fact that we know L-Theanine is highest in shade-grown, high quality green tea. This is because of well-known mechansms involving a breakdown of L-theanine in the presence of sunlight.

The evidence strongly suggests that the best source of L-Theanine is specifically shade-grown green tea. This includes teas like Gyokuro, Matcha, and high grade or specialty sencha Japanese green teas.


+ Indications

  • Depression
  • In combination with caffeine
  • Anxiety
  • To improve memory
  • To improve concentration
  • Alzheimer's disease
  • Certain Cancers
  • Insomnia
  • Chronic stress
  • Cardiovascular disease

+ Contraindications

None noted.

+ Mechanisms

  • Dopaminergic
  • Cerebrovasodilator

General Actions:

  • Relaxant
  • Sedative (Mild)
  • Euphoric
  • Reduces stress
  • Vasodilator
  • Neuroprotective
  • Anxiolytic
  • Antidepressant (Mild)


500 - 750 mg/day

Split up into 2-3 doses per day.

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Chemical Description:

L-Theanine is an amino acid isomer found in the tea plant (Camellia sinensis). It comprises about 50% of the leaves amino acid content, making up about 1-2% of the total dried leaf weight [3]. 

An isomer means that there are two mirror image versions of the same thing. It’s like your right and left hands, they look exactly the same except for the fact that they are each flipped on their axis.

In the same way, there are two versions of theanine, D-theanine, and L-theanine.

L-Theanine is generally the preferred version for use as a nootropic because it’s more common in the plant, and has much more scientific research behind it.

L-Theanine is an amino acid analogue of the proteogenic amino acids L-glutamate and L-glutamine [1]. 

D-Theanine was shown to reduce the absorption of L-Theanine in the gut [7]. 



Still compiling research...


Pharmacognosy of L-Theanine:

Pharmacologically, L-theanine is considered to be a mild sedative, anxiolytic (reduces anxiety), vasodilator (widens blood vessels), neuroprotective, and mild euphoric.

It mimics a similar looking neurotransmitter called glutamate, which is the brains primary stimulating neurotransmitter. By mimicking this neurotransmitter, L-Theanine is able to reduce its effects, effectively turning down the brains hyperactive state.


The benefits for such effects include:

  • Calms overactive thoughts

  • Shortens the time it takes to fall asleep

  • Improves the ability to stay asleep throughout the night

  • Reduces symptoms of anxiety

  • Lowers the sensation of stress


L-Theanine also modulates other neurotransmitters such as dopamine. 

Dopamine has been found to be especially low in those suffering from conditions like ADD or ADHD. L-Theanine was shown in one study to increase the dopamine levels in the brain [2]. 

NeurotransmitterL-Theanines EffectReference
DopamineIncreased release2
GABAIncreased concentration3

L-Theanine Supplements

the tea plant produces two isomers of theanine, D-Theanine, and L-Theanine. L-Theannine is considered the therapeutically active version of the amino acid.

Most commercial products will contain both isomers. Only one product, Suntheanine® was found to have pure L-Theanine. This is because of a patented fermentation process that produces only pure L-Theanine. [6].


Pharmacology and Medical Research:

+ Dopaminergic

L-Theanine was shown to produce a dose-dependant increase in striatal dopamine release via intragastric and intravenous injections [2]. This was shown to be mediated through the NMDA receptors. In this same study, noreadrenaline release was found to be unaffected by the L-Theanine.

+ Neuroprotective

Still compiling research.



No negative side effects were noted in the dosage range of 200-400 mg/day.



Synergistic with caffeine. Works to reduce the side effects of the caffeine, and improve the cognitive enhancing ability. L-theanine is calming and imporves concentration, caffeine stimulates the mind and reduces fatigue and sleepiness. 

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Justin Cooke

The Sunlight Experiment

Updated: March 2017

Recent Blog Posts:


  1. Nathan PJ, 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 6:21–30
  2. Yokogoshi, H., Mochizuki, M., & Saitoh, K. (1998). Theanine-induced reduction of brain serotonin concentration in rats. Bioscience, biotechnology, and biochemistry, 62(4), 816-817.
  3. Goto, T., Yoshida, Y., Amano, I., & Horie, H. (1996). Chemical composition of commercially available Japanese green tea. Foods Food Ingredients J. Jpn, 170, 46-51.
  4. Kimura, R., & Murata, T. (1971). Influence of alkylamides of glutamic acid and related compounds on the central nervous system. I. Central depressant effect of theanine. Chemical and Pharmaceutical Bulletin, 19(6), 1257-1261.
  5. 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, 16(4), 348.
  6. Desai, M. J., & Armstrong, D. W. (2004). Analysis of derivatized and underivatized theanine enantiomers by high‐performance liquid chromatography/atmospheric pressure ionization‐mass spectrometry. Rapid communications in mass spectrometry, 18(3), 251-256.
  7. Desai, M. J., Gill, M. S., Hsu, W. H., & Armstrong, D. W. (2005). Pharmacokinetics of theanine enantiomers in rats. Chirality, 17(3), 154-162.