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L-theanine benefits relaxation without sedation

Published Aug 11, 2022 | Updated Feb 8, 2024

L-theanine is a natural isolated nutrient from green tea which increases the concentration of the chemical messenger, GABA. GABA’s principal role in the brain is to relax the nervous system without sedation. Each capsule contains the same amount of theanine found in 15 cups of tea.

Ideal for:

  • anybody looking to unwind
  • anybody looking to relax but maintain mental performance and clarity.
  • nervous public speakers or nervous travellers

how does theanine work?

theanine is a fast-acting, non-sedative relaxant which reduces the impact of excitatory pathways in the brain, and in doing so it increases the relative GABA concentrations in the brain.

In human studies, theanine also stimulates the production of alpha brain waves which is indicative of a relaxed but alert mental state [12]. It is often referred to as wakeful relaxation [20] exhibiting increased creativity and increased performance under stress as well as decreased anxiety [14].

In patient groups containing subjects with higher anxiety propensity symptoms, theanine has also been shown to reduce heart rate during stressful mental tasks [15]. The relaxation effect of theanine leads to increased GABA concentrations that result in general feeling of calm and wellbeing [6]. However, unlike other conventional calming treatments, theanine does not result in increased drowsiness, slowed reflexes, or impaired concentration [15].

It is absorbed into the bloodstream from the intestinal tract and enters the brain through the leucine-preferring amino acid transporter system [11]. Brain levels increase 30 minutes after ingestion and peak at 5 hours. It does not accumulate in the body but is metabolised in the liver and completely eliminated in the urine within 24 hours. [11].

how is it different?

Most L-theanine is synthetic (e.g. Suntheanine) and its produced as a racemic using ethylamine and l-glutamine.

Brain feed’s L- theanine in a 250mg capsule is extracted from green tea from the mountainous region of Hunan Province in South Central China. It is kept as pure as possible, so you won’t find additives such as lemon balm whose mechanisms of actions, ability to enter the brain or synergistic benefits is unknown.

Browse natural theanine from only £15.99. Additional 15% off your 1st order using code NEW15.


  1. why do we isolate theanine from green tea?

L-theanine is the major amino acid in green tea and constitutes 1-2% of the dry weight of the leaves. To obtain sufficient levels of theanine for a therapeutic dose from whole green tea would also result in high levels of caffeine which can stimulate and produce laxative effects, tannins which can cause stomach irritations & nausea on an empty stomach, and increased amounts of certain anti-oxidants that can hinder iron absorption.

A 2017 review of studies note that high levels of simple green tea extract have been associated with liver damage, jaundice, acute hepatitis like injuries, and even liver failure from catechins within green tea [4].

  1. what should I notice?

Relaxation without sedation. Oral administration of 200mg of theanine in men aged 20 -25 years old also resulted in a reduction in the heart rate [17].

  1. how long does it take to have an effect?

In human studies, increased alpha waves were generated 15 minutes after oral administration [12] and it has been shown to influence the secretion and function of neurotransmitters 30 minutes after ingestion [11]. Theertham et al suggest maximum uptake in the brain is usually within 30-40 minutes.

  1. how do I take it?

1 capsule with a glass of water. Max 2 per day.

  1. does it help with cognition?

In human studies, theanine alone has shown virtually no positive effect on performance.
however, 250mg of theanine has been found to positively interacted with caffeine to enhance reaction time, the accuracy of rapid information processing, mental fatigue, and tiredness [21]. This combination also enhanced the speed of rapid information processing, sentence verification, and word recognition reaction time when caffeine alone did not [13].

  1. will it make me sleepy?

No. it does not promote the onset of melatonin and it is not a sedative. Sleep inducers and sedatives normally induce drowsiness or sleep within an hour [18] whereas theanine, which achieves its maximum uptake in the brain within 30-40 minutes does not induce any sleep or drowsiness in the subjects [19].

  1. are there any side effects or contraindications?

Anybody taking medication for high blood pressure should consult their GP. If you have low blood pressure, discuss theanine with your healthcare provider before starting it.


[1]Nobre et al. (2008) L-theanine, a natural constituent in tea, and its effect on mental state. Asia Pacific Journal. [2]Eschenauer et al. (2006) Pharmacology ad therapeutic uses of theanine. American Journal Health-System Pharmacy.  [3] Haskell et al. (2008) Cognitive and mood effects of caffeine and theanine and alone. Journal of Behaviour Pharmacology. [4]Higashiyama et al. (2011) Effects of l-theanine on attention and reaction time response. Journal of Functional Foods.  [5] Juneja et al. (1999) Effects of l-theanine on the release of alpha brain waves in human volunteers. Trends in Food science & technology.  [6] Juneja et al. (1999). L-theanine—a unique amino acid of green tea and its relaxation effect in humans. Trends in Food Science & Technology.  [7] Kakuda et al. (2000) Inhibiting Effects of Theanine on Caffeine Stimulation Evaluated by EEG in the Rat. Bioscience, Biotechnology, and Biochemistry. 64, 287–293.
[8] Kakuda et al. (2002) Neuroprotective Effects of the Green Tea Components Theanine and Catechins. Biological & Pharmaceutical Bulletin.  [9] Kimura et al. (2007) L-Theanine reduces psychological and physiological stress responses. Biological Psychology. 
[10] Lovallo et al (2006) Cortisol responses to mental stress, exercise, and meals following caffeine intake in men and women. Pharmacology Biochemistry and Behavior.
[11] Lu et al. (2004) The acute effects of L-theanine in comparison with alprazolam on anticipatory anxiety in humans. Human Psychopharmacology . Clin. Exp. 19, 457–465. 
[12] Micallef et al. (2001) A double blind parallel group placebo-controlled comparison of sedative and amnesic effects of etifoxine and lorazepam in healthy subjects. Journal of Fundamental Clinical Pharmacology. [13] Navarro et al. (2017) Liver injury from herbal and dietary supplements. Journal of Hepatology. [14] Ozeki et al. (2008) a study of l-theanine and daytime drowsiness. Japanese Journal of Physiological Anthropology.
[15] Song et al. (2003) Effects of Theanine on the Release of Brain Alpha Wave in Adult Males. Korean Journal of Nutrition.
[16] Terashima et al. (1999) Time-dependent Changes of Amino Acids in the Serum, Liver, Brain and Urine of Rats Administered with Theanine. Bioscience, Biotechnology, and Biochemistry. 
[17] Theertham et al. (2015) In Search of a Safe Natural Sleep Aid. Journal of the American College of Nutrition.[18] Unno et al. (1999) Metabolism of theanine, gamma-glutamylethylamide, in rats. Journal of Agriculture & Food Chemistry. [19] Yokogoshi et al. (1998) Effect of theanine, r-glutamyethylamide, on brain monoamines and striatal dopamine release in conscious rats. Journal of Neurochemical Research. [20] Bryan (2008). Psychological effects of dietary components of tea: caffeine and L-theanine. Journal of Nutrition Reviews. 
[21] Borzelleca et al. (2006) A 13-week dietary toxicity and toxicokinetic study with l-theanine in rats. Food and Chemical Toxicology. 

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