L-Theanine: Benefits, Uses, Dosage, and Side Effects

An all-rounder nootropic to ease anxiety and boost performance.

L-Theanine: Benefits, Uses, Dosage, and Side Effects

A calming and anti-anxiety nootropic that has gained a lot of popularity, l-theanine is a compound that comes backed by substantial research for its health benefits.

If you are a tea drinker, you may already be familiar with this relaxing compound found in tea that helps promote relaxation and focus during periods of stress. Plus, it does so without causing drowsiness.

And if you are new to its potential as a nootropic, then we will walk you through this fantastic nutrient that actually makes drinking tea all the more beneficial for your health.


    What is L-Theanine?

    The evergreen tea plant Camellia Sinensis gets its potent qualities from l-theanine, an amino acid found in its leaves. It can be sourced from any form of tea, whether it is black, white, oolong, or green, as long as it comes from the Camellia Sinensis plant.

    In a showdown between green and black tea, both types have similar health benefits. However, green tea has the highest l-theanine concentrations, while black tea has more caffeine.

    Scientifically, L-theanine goes by the name of gamma-ethylamino-L-glutamic acid. It takes about 50% of green tea’s free amino acid content.

    It was first identified in 1949 and then successfully isolated from green tea a year later. L-theanine has been the subject of intensive research since 1950 in both animal and human studies, with growing evidence establishing its therapeutic potential.

    How Does L-Theanine Work In The Brain?

    For the most part, L-theanine is an amino acid that gives green tea its active properties. Its mechanism of action makes it the most potent component in tea, yielding physical and mental benefits.

    It is a biologically active component that can pass through the blood-brain barrier to impact the brain neurochemically, acting as a neurotransmitter.

    Structurally, it resembles glutamate and GABA, the brain’s excitatory and inhibitory neurotransmitter system, respectively. It is a derivative of glutamic acid, the brain’s primary excitatory neurotransmitter, and can bind glutamate receptors.

    In this capacity, it can induce profound changes in glutamic acid neurotransmission by regulating the inhibitory and modulatory neurotransmitters’ levels.

    What Are The Benefits of L-Theanine?

    Green tea and even white or black tea is packed with flavonoids and catechins. This gives tea multiple antioxidant properties that can help many areas of cognition and physical health.

    The antioxidant content found in green tea can help reduce oxidative stress and prevent wear and tear in brain cells that may impair cognitive function.

    Or, l-theanine may help with the physical tasks of improving sleep quality, lowering blood pressure, regulating stress levels, and promoting relaxation.

    Improves Sleep

    L-theanine consumption is often associated with enhanced sleep quality by many people. Several studies suggest that l-theanine may help people relax before bedtime. This can help with getting to sleep easier and experiencing a more profound sleep as well.

    One 8-week randomized, double-blind placebo study investigated the effect of l-theanine supplements on sleep quality by administering 450-900 mg of l-theanine daily.

    Participants suffered from generalized anxiety disorder and were taking antidepressants. Study findings showed greater sleep satisfaction experienced among the people taking the supplements (1).

    Other studies show L-theanine to reduce the resting heart rate indicating its ability to boost relaxation during sleep. It improves the quality of sleep not by acting as a sedative but by lowering anxiety and promoting a sense of calm.

    Enhances Focus and Attention

    One of the primary mechanisms of l-theanine seems to be improving brain wave frequency. Of concern here is an increase in alpha wave activity that works wonders for mental performance.

    An increase in alpha brain waves is associated with a state of wakeful relaxation, alertness, and concentration without the edge of anxiety.

    Research suggests that l-theanine supplementation increases alpha waves within 30 minutes of ingestion (2).

    Some research has also looked at whether taking L-theanine for ADHD is really effective in benefiting people with this disorder.

    Studies investigating Attention Deficit Hyperactivity Disorder in children showed that a combination of L-theanine with caffeine seemed to improve overall mental performance by minimizing mind wandering during an attention task (3).

    Reduces Stress, Anxiety, and Depression

    Tea drinkers often report that drinking green tea makes them feel relaxed without causing drowsiness.

    This is due to the effects of l-theanine on managing neurotransmitter levels. For instance, research suggests that it increases GABA levels and other brain chemicals, keeping anxiety in check, regulating emotions, and boosting quality sleep (4).

    A higher level of calming brain chemicals allows you to relax, sleep better, and deal with stress more efficiently.

    At the same time, it also lowers excitatory brain chemicals such as glutamate and acetylcholine. Any elevation in such excitatory chemicals’ levels is associated with feelings of anxiety and stress and may even increase the risk of mental disorders.

    A heightened state of alpha brain wave activity is also correlated inversely with cortisol levels. This means that as alpha waves increase, cortisol levels decrease, which also reduces stress.

    As a result, l-theanine helps with depression and is considered beneficial for stress management because it can also reduce heart rate when resting.

    Increases Cognitive Performance

    Healthy cognitive function is strongly linked to levels of stress and anxiety. People with a high level of stress experience a significantly adverse impact on their ability to make decisions, and may also damage brain cells due to increased pressure.

    Studies in this area present evidence that l-theanine helps to support memory, concentration, and focus given its neuroprotective and stress-relieving effects (5).

    Additional research also suggests it to be safe with positive effects when L-theanine and caffeine are combined (6).

    Promotes Weight Loss

    An interesting effect of green tea consumption is that its l-theanine component can trigger a savory taste known as umami flavor. Research results suggest that this flavor may reduce appetite, which can help with weight loss.

    This makes l-theanine an amino acid often used in pre-workout supplements to ramp up performance and fat loss.

    The combination of l-theanine, caffeine, and green tea catechins has been researched for its effects on weight loss. One study found that the l-theanine and caffeine content of the tea leaves reduced triglyceride levels.

    The researchers indicated both compounds to be involved in the suppressive effects of green tea on body weight and fat accumulation.

    Another randomized, double-blind placebo study looked at the catechin component’s effects concerning visceral fat loss. The study results showed that 12 weeks of consuming green tea positively impacted losing visceral fat (7).

    Boosts The Immune System

    Among other benefits of l-theanine, its antioxidant effects help boost an individuals’ immunity. When it was studied alongside another green tea component, EGCC, the results were promising regarding its anti-inflammatory activity.

    One study looked at the polyphenol EGCG and found that it could cause a higher production of regulatory T cells.

    T cells are white blood cells essential to the immune system and lie at the core of adaptive immunity. Animal studies show that EGCC increased both the number and frequency of regulatory T cells.

    Researchers see this as helpful in controlling the immune response (8).

    Reduces Blood Pressure

    An effect of L-theanine is that it can readily cross the blood-brain barrier.

    One way this can help is by lowering the risk of stroke. A stroke occurs with some kind of blood blockage to the brain. This can happen either due to a lack of blood flow or due to bleeding.

    The risk of stroke increases continuously with high blood pressure levels. High blood pressure damages arteries triggering conditions where they may clog or burst more easily. Weakened arteries in the brain resulting from elevated blood pressure levels put people at a much higher risk of stroke.

    One way l-theanine helps is that it helps release nitric oxide. Nitric oxide stimulates vasodilation and increases cerebral blood flow.

    This mechanism not only ensures improved blood flow throughout the body but also keeps blood pressure in check.

    Supports Tumor and Cancer Treatment

    Preliminary evidence suggests that l-theanine may play a protective part in supporting cancer treatment. The ability of l-theanine to bind glutamate receptors may have a direct effect on tumor cells.

    The cancer-related benefits are exerted by inhibiting glutamate transport into tumor cells and thus decreasing intracellular glutathione levels. This also inhibits the outflow of chemotherapeutic agents, causing them to accumulate in tumor cells.

    L- theanine seems to have the opposite effect in healthy cells where it helps the maintenance of intracellular glutathione levels, protecting them from oxidative stress (9).

    It also does not have the harsh effects of conventional cancer drugs and could be considered a gentler treatment option. However, more studies are needed to establish its efficacy for treating cancer.

    Other Benefits

    Some other research areas where the effectiveness of l-theanine has been tested include using it as an adjuvant to manage psychotic disorders.

    For this purpose, researchers divided participants into two groups of patients with schizophrenia or schizoaffective disorder. Participants were randomized to use either L-theanine or placebo while continuing with their antipsychotic medication.

    Patients with schizophrenia receiving l-theanine supplements experienced a moderate reduction in symptoms and anxiety (10).

    However, this preliminary research of small and more prominent, randomized, placebo-controlled studies is warranted to replicate these findings.

    The L-Theanine and Caffeine Synergy

    Caffeine is often paired with l-theanine for its synergistic impact. For most people, caffeine intake is stimulatory, while l-theanine works as a relaxant.

    As an energy booster, caffeine yields instant mental and physical effects, but it will present side effects if consumed in high doses. The most typical ones that people experience include irritability, anxiety, energy crashes, jitters, and dizziness.

    On the other hand, L-theanine balances the highs of caffeine with its calm alertness but without bringing on drowsiness. So, while it balances excitatory responses, it does so without taking anything away from the energy aspect.

    Other noticeable benefits include enhancing cognitive skills like attention span, processing visual information faster, and increasing accuracy when switching from one task to another.

    As such, the combination of caffeine with l-theanine is an ideal one, and the two are often dosed together for optimal health results.

    How To Take L-Theanine?

    Green tea has a historical place in both Ayurvedic and Traditional Chinese Medicine. Both systems, however, recommended a different amount of tea based on the condition being treated.

    For the most part, people may drink an average of three cups daily up to an upper limit of ten cups a day for specific health conditions.

    Available forms

    L-theanine is available in forms such as capsules, pills, and tablets. Or, you can use it as tea.

    Many people who self-medicate use it as a dietary supplement to manage their stress and anxiety levels. Others opt for the tea form to use for relaxing the mind.

    One cup of tea contains anywhere from 25-60 mg of l-theanine.

    L-theanine readily crosses the blood-brain barrier within 30 minutes and continues to increase. The effects of l-theanine reach maximum levels approximately after 5 hours.

    To get a more considerable amount of l-theanine, you can turn to the supplement form instead. There is also a patented form of l-theanine, called Suntheanine, that simulates the natural manner in green tea leaves emerging in a more purified and effective compound.


    For an l-theanine supplement, typical dosing starts at 200 mg of l-theanine every 4-6 hours.

    • For nootropic purposes, doses can range from 100mg to 200 mg.
    • For insomnia, ADHD, or hyperactivity, the recommended dose is 200 mg.

    Studies show that patients with schizophrenia were given 400mg/d of l-theanine alongside their antipsychotic medication safely.

    A warm cup of tea before bedtime can calm the nerves and help you relax from sleep-related issues. Or take a dose 30 – 60 minutes before bedtime.

    You can take the best l-theanine supplements either with or without food. Some people feel that taking it on an empty stomach may kick in results faster than with food. This is similar to drinking coffee on its own versus taking it with a meal.

    Does L-Theanine Have Side Effects?

    L-theanine is considered safe when taken in the recommended amounts for short-term use. Users are advised to limit this from about 3 to 16 weeks.

    There have been no reports of l-theanine causing any severe side effects though it does have some drug interactions. Ordinary experiences include headaches, nausea, and irritability.

    Typical interactions include blood pressure medications and stimulants.

    The safety of l-theanine has not been established for pregnant and nursing mothers, although drinking one to two cups of green tea is considered safe for most women.


    L-theanine can be a standalone supplement or used in a nootropic stack for improving memory, attention, mood, and relaxation.

    The vast amount of research backing its potency makes it one of the most popular and safest nootropics to experiment with. It is ideal for managing the body’s stress response to excitatory chemicals and to use as a nootropic for sleep.

    For us, this makes l-theanine one of the best nootropics to add to any health regimen, and we highly recommend everyone give this all-rounder supplement a try.


    Does L-Theanine increase dopamine?

    L-theanine increases dopamine production, with multiple studies verifying this mechanism. This action has an antidepressant impact and improves mental performance.

    Does L-Theanine increase serotonin?

    L-theanine also increases serotonin levels that bring on feelings of well-being and happiness. It also encourages brain cells and nerves to communicate better with each other.

    The hormone also has an integral part to play in sleep and digestion.

    Can you take L-Theanine and Melatonin together?

    L- theanine, and melatonin both possess sleep-inducing qualities and have been used in supplements together.

    This seems a safer way to use the two together as the dosage would be more regulated instead of taking a separate supplement for each.

    Can you take L-Theanine and GABA together?

    L-theanine and GABA, when used together, yield a rapid and robust synergistic result.

    Both help balance the nervous system, promote quality shuteye, and contribute to optimal health.