L-theanine is an amino acid extracted from the leaves of Camellias Sinensis — the fancy-pants name for the common green tea plant. It’s actually responsible for some of the savoury notes in green tea and is becoming a highly popular natural and safe calming agent.

Taken to reduce ailments such as anxiety, L-theanine performs similar actions to gamma-aminobutyric acid (GABA), an inhibitory neurotransmitter that blocks excitatory responses in the brain. L-theanine blocks these excitatory responses. As a result, it can lower blood pressure, decrease heart rate, and reduce stress hormone levels in the body.

A typical cup of brewed green tea will contain 8 mg of L-theanine. 

Also known as a Nootropic — a cognitive enhancer — L-theanine can help improve cognitive function. Its mechanisms aren’t all completely understood yet, but they’re very well documented. Touted as the safest nootropic out there, even more so than the caffeine from your coffee! 

Ārepa Nootropics are proud to include 200mg of pure L-theanine in every serving of our natural plant-based nootropic brain food.Equivalent to 25 cups of green tea.

Here's a list of the 5x amazing benefits of L-theanine - the friendly amino acid.


Think, for a moment, of the many drawbacks related to caffeine. It causes stress, anxiety, restlessness, and even increases blood pressure. L-theanine works to correct these negative qualities, thus ensuring our caffeine intake experience is far more pleasant. [1]

Because caffeine replaces adenosine in the brain, our minds are stimulated and running a bit too free. But when we add L-theanine to the conversation, that excitatory response is inhibited, and stress is managed as a result. 

Many of caffeine’s negative properties stem from the fact that it’s a vasoconstrictor. This means that drinking a cup of coffee will temporarily make your blood vessels smaller. With less room to flow, your blood pressure can skyrocket, causing your heart to beat faster and your body to sweat. For many people, their body interprets these symptoms as those of stress or anxiety and acts accordingly.

L-theanine not only helps to promote relaxation, helping to reduce stress brought on by that cup of coffee, but it also combats the vasoconstrictive properties of caffeine [2]. It allows your blood to flow as normal, preventing your body from panicking. You also don’t have to worry as much about the adverse health effects of raising your blood pressure, such as damaged arteries, heart disease, and even an increased risk of aneurysm. [3]



Most side effects of relaxants are that they also induce drowsiness, fortunately for L-theanine it is non-drowsy [4]. After crossing the blood-brain barrier, L-theanine inhibits the binding of glutamic acid to glutamate receptors in the brain and has been considered to cause anti-stress effects by inhibiting cortical neuron excitation.” [5] 

Studies in healthy adults show that orally administered L-theanine reduces anxiety and attenuates blood pressure increases under conditions of physical or psychological stress [6]. In a study looking at the effects of L-theanine on the stress response (using a mental arithmetic task as an acute stressor), compared to placebo, L-theanine reduced heart rate and salivary immunoglobulin A responses (S-IgA) in the subjects [7]. Researchers attributed these effects to an attenuation of sympathetic nervous activation. Animal studies suggest that L-theanine increases brain levels of various neurotransmitters and that it has micromolar affinity for AMPA and kainite receptors (as an antagonist) and NMDA receptors (as an agonist) [8].

Theanine has also been shown to boost levels of GABA, as well as other hormones and compounds that promote calm, focus, regulated mood, and more. [9]



In a study on anxious university students put through stressful cognitive testing, the students on L-theanine had significantly enhanced activity of alpha brain waves, descending heart rate, elevated visual attentional performance, and improved reaction time response among high anxiety propensity subjects compared to a placebo. [10]


Alpha brain waves are associated with a state of wakeful relaxation deemed by psychologists as 'the zone'. That’s the state of mind you experience when meditating, being creative, or letting your mind wander in daydreaming. Alpha waves are also present during REM sleep. L-theanine appears to trigger the release of alpha-waves [11], which enhances relaxation, focus, and creativity. One of the appealing aspects of L-theanine is that it works to relax without sedating. That can make L-theanine a good choice for people who are looking to enhance their “wakeful relaxation,” without worrying about becoming sleepy and fatigued during the day.

Fun fact - Ārepa is Te reo Māori transliteration for alpha - learn more about why we chose this name here.  


Antidepressants are now among the most widely prescribed medications worldwide, and data suggest that the use of these drugs is increasing. The problem is that for a substantial proportion of patients antidepressants are ineffective and the side effects can be intolerable. 

An exciting new study from Japanese researchers has found that L-theanine significantly reduced symptoms of depression, and improved cognitive functioning in people with depression. In this study, 20 people with major depressive disorder were given 250 mg L-theanine per day for 8 weeks and assessed for cognitive functioning, sleep, and depression. The authors of this study concluded that L-theanine was safe (no adverse side effects observed) and had multiple benefits on depressive symptoms including reductions in anxiety and cognitive impairments, and improved sleep. [12]



Sleep deprivation is associated with an elevated risk of various diseases and leads to poor quality of life and negative socioeconomic consequences. Sleep inducers such as drugs and herbal medicines may often lead to dependence and other side effects. L-Theanine has effects associated with conventional sleep inducers without any known side-effects. A study found 200mg boosted participants quality of sleep but not the duration suggesting it was through its ability to reduce stress and induce a calming state allowing the brain to fall asleep naturally, rather than through sedation which often causes increased sleep duration. [13]

Have a child with ADHD? A study in 98 male children given a daily dose of L-theanine found it is a safe and effective means of improving aspects of sleep quality in boys diagnosed with ADHD. Since sleep problems are a common co-morbidity associated with ADHD, and because disturbed sleep may be linked etiologically to this disorder, L-theanine may represent a safe and important adjunctive therapy in childhood ADHD [14]

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