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Home Learn What is L-theanine? Benefits, History, and Science of Green Tea Extract


Home Learn What is L-theanine? Benefits, History, and Science of Green Tea Extract

What is L-theanine? Benefits, History, and Science of Green Tea Extract

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For years, studies have trickled in regarding the potential health benefits enjoyed among members of Asian cultures that revere green tea. While these stories of hope have certainly helped drive green tea stocks higher, most consumers have, alas, been barking up the wrong “tea.”

L-Theanine is a non-essential amino acid that has gained popularity in recent years for its various health benefits. The ingestion of L-Theanine can be primarily found in green tea and is known to have a range of positive effects on the human body, including promoting relaxation, improving cognitive function, and supporting heart health. In this article, we will explore what L-Theanine is, its effects, and the benefits of incorporating this amino acid into your diet.

L-theanine: The botanical amino acid present in green tea leaves, processed in the body into theanine.

Theanine: A non-essential amino acid that provides beneficial effects. With or without the “L,” theanine remains the same.

In addition to stimulating the senses, theanine also provides deep relaxing effects that help soothe anxiety and facilitate sleep. Plus, this nootropic may also lower your blood pressure, improve your immunity, and boost your health and well-being in other ways. You’ll learn all about this important component of Feel Nootropics as we continue.


What is L-theanine? (green tea extract)

L-Theanine is an amino acid found primarily in tea leaves, especially in green tea. It is a non-essential amino acid, which means our bodies can produce it in small amounts, but we can also obtain it through our diet or supplements. Theanine has a unique structure that allows it to cross the blood-brain barrier, making it particularly effective in influencing brain function and neurotransmitter activity¹.

Once in the body, L-theanine is generally called just “theanine,” and this isomer is the enantiomer of D-theanine. An enantiomer is the mirror opposite of another isomer contained in a plant or another chemical system, and D-theanine has very different effects from L-theanine. The “D” form of theanine isn’t beneficial, so it hasn’t been studied very extensively.

Since theanine is structurally similar to glutamate, a major excitatory neurotransmitter, it bonds to glutamate receptors to increase GABA, serotonin, glycine, and dopamine levels throughout your body. Rather than directly stimulating your central nervous system, these widespread, gentle effects subtly facilitate better mental clarity and physical well-being.

Unlike the nervous system stimulant caffeine, which is also present in green tea, theanine does not exert a direct stimulatory effect. By increasing your overall levels of various critical neurotransmitters, however, theanine could provide a rush of energy just like a more wholesome version of caffeine.

Or, it might help you relax and get to sleep at the end of a long day. Like most nootropics, theanine increases your brain’s ability to react to the circumstances in which your body happens to find itself on a given day. Think of Feel Nootropics as empowerment in a bottle—it isn’t soo much what nootropics do for you, but what they free you to accomplish.


Why is it called L-theanine?

Theanine’s official chemical name is L-γ-glutamylethylamide, and L-theanine is a contraction of this nearly-unpronounceable scientific designation. Specifically, “L-theanine” refers to the “positive” enantiomer present in green tea leaves, and just plain “theanine” is a general term that refers to this amino acid wherever it may be present.

What are the benefits of L-theanine?

The theanine in tea is the primary source of L-Theanine for most people. It is a naturally occurring compound in the leaves of Camellia sinensis, the plant from which all types of tea are derived. Green tea, in particular, is known to have the highest concentration of L-Theanine (2). While black tea also contains L-Theanine, the fermentation process during its production reduces the overall levels of this amino acid.

Despite being a component of green tea, the benefits of theanine aren’t limited to stimulation alone. It’s true that theanine can provide a stimulatory effect, but it’s just as likely to relax you, help with your blood pressure, or fight illness. Let’s take a look at each of theanine’s major benefits in turn


One of the most well-known effects of L-Theanine is its ability to promote relaxation and reduce stress and cortisol. Studies have shown that L-Theanine can increase the production of alpha brain waves, which are associated with a state of relaxed alertness (5). This allows the body to unwind and the mind to stay focused without feeling drowsy.

Unlike some more experimental substances, theanine’s accepted status within contemporary pharmacology means that quite a few clinical (human) studies, placebo-controlled trial or randomised controlled trial have been conducted to determine this amino acid’s effects. Anxiety has been a major focus of potential theanine therapy—here are a few examples of seminal studies in the field:

1. L-Theanine Relieves Positive, Activation, and Anxiety Symptoms in Patients With Schizophrenia and Schizoaffective Disorder: An 8-Week, Randomized, Double-Blind, Placebo-Controlled, 2-Center Study

2. Anti-stress effect of theanine on students during pharmacy practice: Positive correlation among salivary α-amylase activity, trait anxiety and subjective stress

3. The acute effects of L‐theanine in comparison with alprazolam on anticipatory anxiety in humans

As you read through this research, you’ll find a common theme. Theanine appears to work especially well for anxiety when comorbid conditions are present, which means related psychiatric conditions that usually exacerbate each other’s symptoms. Anxiety rarely operates alone, and by quieting the constant flow of worrisome or painful thoughts that fill our heads, we become free to focus on what’s most important. The research supports considering theanine as a powerful anxiety aid.


The research supporting theanine’s effects on focus is shakier but still present. Here’s an example of a relevant study:

The combination of L-theanine and caffeine improves cognitive performance and increases subjective alertness

As you can see, this study used theanine in conjunction with caffeine, which instantly raises important questions. The amount of theanine used more than doubled the amount of caffeine, but it’s possible that the noted attention-related effects could be due to a synergy between the two substances, not the effects of theanine on its own.

Regardless, reduced anxiety naturally leads to increased focus. Anxiety can be like a low-grade infection, making everything harder. Calming your mind will inevitably lead to a greater feeling of focus and control.

L-Theanine has also been shown to improve cognitive function and memory. Research suggests that the amino acid can enhance learning and memory by modulating the release of neurotransmitters and influencing brain-derived neurotrophic factor (BDNF), a protein that supports the growth and maintenance of neurons (6). Additionally, L-Theanine may help to protect the brain from age-related cognitive decline by reducing oxidative stress and inflammation(7).


L-Theanine has been shown to improve sleep quality by promoting relaxation and reducing anxiety. A study conducted on individuals with attention deficit hyperactivity disorder (ADHD) found that L-Theanine supplementation led to improvements in sleep efficiency, sleep onset latency, and sleep quality. Another study involving healthy adults found that L-Theanine helped to counteract the negative effects of caffeine on sleep, reducing the time it took to fall asleep and increasing sleep duration.

While it does not act as a sedative, it can help individuals fall asleep more easily by promoting relaxation and reducing anxiety (8). Moreover, L-Theanine has been shown to improve sleep quality and efficiency, leading to more restorative rest and a reduced need for sleep medications (9).

In 2011, Alternative Medicine Review published a large clinical trial conducted into a big-pharma form of theanine. While the conflict of interest is obvious, the results speak for themselves. Here are some of the key findings of one of the largest human studies into theanine ever conducted:

“L-theanine at relatively high doses was well tolerated with no significant adverse events. This study demonstrates that 400 mg daily of L-theanine is safe and effective in improving some 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.”

Once again, we find theanine described in the context of comorbidity, in this case relating to the connection between disturbed sleep and ADHD. It should be clear by now that theanine’s main effect is in boosting your nervous system’s overall ability to prevent major disturbances and promote long-term neurological healing and well-being. But, we’re not done discussing theanine’s effects on sleep. Let’s check out a couple more studies:

L-theanine partially counteracts caffeine-induced sleep disturbances in rats

Natural systems often balance each other. It should come as no surprise, then, that theanine appears to counteract some of the sleep disturbances caused by caffeine.

GABA and l-theanine mixture decreases sleep latency and improves NREM sleep

Theanine already increases GABA, but this study shows that sleep is improved even more when these two brain-boosters are paired.

Apart from anxiety, sleep is the most well-researched application of theanine. Who doesn’t get a better night’s sleep when there are fewer worries rattling around?

Blood pressure

Theanine relaxes you so much that it even lowers your blood pressure. Here’s the science:

Reduction Effect of Theanine on Blood Pressure and Brain 5-Hydroxyindoles in Spontaneously Hypertensive Rats

This study observed the effects of both theanine and glutamine on rats with hypertension. While glutamine didn’t have any effect, the researchers noted significant decreases in blood pressure at high doses of theanine.

Effects of L-theanine or caffeine intake on changes in blood pressure under physical and psychological stresses

In determining how well caffeine and theanine prevented increases in blood pressure both together and separately, the facilitators of this international study noted the following results:

“L-theanine significantly inhibited the blood-pressure increases in a high-response group, which consisted of participants whose blood pressure increased more than average by a performance of a mental task after placebo intake. Caffeine tended to have a similar but smaller inhibition of the blood-pressure increases caused by the mental tasks.”


A 2010 study demonstrated that combining cystine and theanine increases overall immune function in animal models. In 2016, researchers sought to substantiate these findings with similar experiments but using only theanine:

L-Theanine Improves Immunity by Altering TH2/TH1 Cytokine Balance, Brain Neurotransmitters, and Expression of Phospholipase C in Rat Hearts

There aren’t any human studies on the effects of theanine on immunity yet. Animal models, however, paint a clear picture of this amino acid’s ability to improve overall immune regulation. While separate, the immune system is intricately connected to the nervous system, and neurotransmitters play important roles in healthy immune function.

Cardiovascular Health

L-Theanine may also have beneficial effects on cardiovascular health, particularly in the context of blood pressure regulation. Some studies have suggested that the amino acid can help to reduce blood pressure in individuals with hypertension, possibly by modulating the release of certain neurotransmitters and promoting relaxation (10). Additionally, L-Theanine has been shown to improve endothelial function, which is essential for maintaining healthy blood vessels and preventing cardiovascular diseases (11).

Where did L-theanine originate, and how were its beneficial properties discovered?

Most types of tea contain small amounts of theanine, and this amino is highly concentrated in all forms of green tea as well as certain mushroom species. The pinnacle of green tea, both in the umami taste and theanine content, is Gyokuro.

Both Chinese and Japanese traditional medicine call for the extensive use of green tea, which many East Asian cultures view as practically interchangeable with water. While we can’t say great things regarding the health benefits of the caffeine in green tea, it’s clear that ancient Asian healers were onto something when it comes to theanine.

Research into green tea led to the discovery of theanine and its side effects in 1949, and by 1950, this nootropic had already been isolated from Gyokuro green tea leaves. Basing their research on ancient medical wisdom from the region, pioneering international scientists banked on the universal appeal of theanine. Their gamble paid off, and L-theanine from green tea is now one of the world’s most popular nootropics.

Where does Gyokuro green tea grow?

Japanese tea breeders were the first to cultivate Gyokuro, which has a fuller, more potent taste than other green tea breeds of Japan. Gyokuro has since spread throughout China and, to a lesser degree, Korea.

You can get L-theanine from any green tea, not just Gyokuro. This breed, however, was the first to ever be used for theanine production, and purists still swear by Gyokuro. Wherever you get your theanine, it will have the same effect on your nervous system. Better sources may be safer, however.

Secrets and science behind L-theanine

Theanine is the sleeper agent within the buzz caused by green tea leaves. Almost everyone in both China and Japan still drinks cha, a common name for green tea in many regional dialects. Cha literally just means “tea,” which goes to show just how important this beverage is to the East Asian lifestyle.

Perhaps its green tea we have to thank for the curious longevity displayed in many rural Japanese and Chinese communities. We can’t help but feel a little overwhelmed, however, at all the caffeine you have to consume to enjoy the benefits of theanine in green tea. Whether you like the buzz this stimulating bean provides or not, it’s good to have the option to enjoy theanine solo.

Why does L-theanine work, and how?

Theanine mainly functions by boosting neurotransmitter levels throughout your brain. These swarms of nervous system messengers ripple throughout your body, boosting your defenses and soothing your spirit.

As an antidote to everyday stresses and stress responses, L-theanine gently arouses the mind while calming the emotions. For anyone who occasionally (or often!) gets strained by the demands of professional and personal life, this ancient green tea extract can be just the thing to attain inner balance and exude total peace.

L-theanine in biohacking/brain-hacking

The basic principle of biohacking is to boost your body’s ability to get the job done with modern tools, and your brain is the logical place to start. Rather than overloading your system like a real-life “limitless pill,” theanine gradually helps your nervous system accept higher concentrations of beneficial neurotransmitters. To ensure the brain operates like a fully-functional computer, continuous maintenance with brain-boosters like L-theanine is essential.

How to take L-theanine

Most theanine formulations are in capsule form, but oral tinctures may also be available. It’s also possible to consume L-theanine in green tea alongside large doses of caffeine.

L-theanine in Ayurveda and Chinese medicine

Green tea wasn’t widely used in Ayurveda due to a general perception that caffeine was toxic. Indians did and continue to consume vast volumes of tea every year, but that doesn’t mean this beverage figures prominently in regional medical systems.

Chinese medicine, however, is another matter entirely. So much of Chinese culture centres around green tea that it might as well be the national beverage. A peer-reviewed paper covers many of the details surrounding medical tea drinking in both Ancient and modern China. Let’s start with some excerpts:

“According to the classical work of Li Shizhen (李時珍 Lǐ Shí Zhēn) of the Ming Dynasty, “tea is cold and lowers the fire.” Since fire (inflammation) causes many diseases, could tea be effective in the prevention of many diseases?”

“The molecular mechanisms for cancer prevention by tea constituents have been extensively studied and reviewed. The antioxidant actions of tea catechins could be an important mechanism for cancer prevention.”

It’s possible that Ancient Chinese medical practitioners understood that green tea could serve as an anti-inflammatory. If so, other modern medical discoveries regarding theanine could have been mirrored thousands of years ago in the Far East.

How long have people been using L-theanine?

Most sources agree that people have consumed green tea in China for at least 5,000 years, though no definitive historical records exist. In its isolated form, L-theanine from green tea has been on the international market since the mid-1950s.

Why we chose L-theanine for Feel Nootropics

When you think about green tea, “stimulant” is the first thing that comes to mind. Theanine breaks with convention, however, as a cha constituent that relaxes and soothes rather than tenses and excites. Every force has its equal opposite, and theanine appears to balance caffeine while subtly accentuating its effects.

Caffeine isn’t necessary, however, to enjoy the very real benefits of this time-honoured nootropic. Instead, why not boost this botanical amino acid with complementary nootropics like 5-HTP, Gotu kola, and bacopa monnieri? When nothing but a boosted brain and clear mind will do, Feel Nootropics is the solution.

How long does it take for L-theanine to work?

As one of the more psychoactive of the mild nootropics, L-theanine may exert noticeable effects almost immediately. It’s more likely, however, that you’ll experience the benefits of this nootropic unfold over the course of weeks and months as elevated neurotransmitter levels stabilise and a new outlook on life manifests.

How much L-theanine should I take?

There are no official guidelines on L-theanine dosing. An article by James Lake, MD on Psychology Today Blog, however, suggests that doses between 50 and 200mg are appropriate. Feel Nootropics contain 200mg of L-theanine per capsule. 

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About the author
Katie Hipwell - Katie is an AfN Registered Nutritionist (RNutr) with a specialism in food and is Head of Nutrition at Feel. Katie has worked in the food supplement industry for 10 years. She has completed a Master's degree in Human Nutrition and an undergraduate degree in BSc Sport and Exercise Nutrition.
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