10 Health Benefits of L-Theanine Supplements (Side Effects + Dosage)

10 Health Benefits of L-Theanine Supplements (Side Effects + Dosage)

We live in an age where we can have access to anything we want with the click of a button. Machines have automated difficult tasks. Our phones have given us access to a wealth of information in the palm of our hands. Despite these modern conveniences, we have never felt more exhausted and drained of energy as a society. Anxiety, depression, and stress levels are at an all-time high. Can the benefits of L-theanine help improve our psychological and physiological state?

Supplements and nootropics can work great for boosting energy, especially if they improve sleep quality simultaneously. A YouGov survey reveals that 6 out of 7 Americans wake up feeling tired and fatigued every day. Insomnia is a real problem, and irregular sleeping patterns can have a negative impact on almost every facet of your life. One common natural remedy for relaxation is green tea. It also receives praise for being able to improve mental function and cognition. This advantage exists because of one main ingredient in green tea: L-theanine.

But what is L-theanine good for? In today’s article, we will discuss the numerous L-theanine health benefits. These benefits include its effects on stress, anxiety, depression, sleep quality, brain function, and much more. We will also review the potential for side effects and provide our dosage recommendations for L-theanine supplements.

What is L-Theanine?

L-theanine What is L-theanine? Camellia sinensis leaves contain high amounts of L-theanine, a non-essential amino acid. These are the same leaves used to make green tea. L-theanine was discovered in 1949 by Japanese scientists. They were extracting various compounds from the tea leaves. People consumed green tea for hundreds of years in Japan due to its multiple health benefits. Today, science has verified many of the claims regarding these L-theanine benefits.

L-theanine is a psychoactive substance capable of crossing the blood-brain barrier. It crosses the barrier within 30 minutes of oral ingestion. It can do so at doses as low as 50mg. Its fast-acting nature allows it to affect the brain directly, enhancing cognitive function.

In doing so, it quickly provides a feeling of relaxation and calm throughout the body. Drinking green tea or black tea is the only way to consume L-theanine dietarily. This restriction and the general low quantity of theanine present in tea means that most of us are deficient in this amino acid.

Scientists know that L-theanine supplements do several things. Its mechanism of action involves elevating levels of gamma-aminobutyric acid (GABA), serotonin and dopamine. All three compounds are neurotransmitters responsible for regulating many cognitive functions. These functions include mood, energy, and feelings of alertness.

GABA lowers stress signals in the brain, helping one feel more relaxed to achieve deep sleep. This response is ideal for people who are suffering from social anxiety or insomnia. Increases in serotonin and dopamine contribute to an overall better mood and sense of well-being. L-theanine can work wonders for benefiting your mental health.

How Much L-theanine is in Green Tea?

There are technically two forms of theanine in the leaves: D-theanine and L-theanine. The “L” variation is most dominant at 98%. L-theanine makes up 1-2% of the total dry weight of tea. For every 200mL serving of green tea, there is 25-60mg of L-theanine. You can choose to take an L-theanine supplement or get it by drinking more green tea. Black tea also contains L-theanine, but green tea has more.

10 L-Theanine Health Benefits and Uses

1. Reduces Stress & Anxiety

L-theanine for Stress & Anxiety The benefits of L-theanine are most prominent for those looking to improve their mood. People started using L-theanine for anxiety and depression ages ago. Eventually, it became famous in the health world as a potent anxiolytic supplement. L-theanine works by reducing chemically-produced signals responsible for negative emotions. Furthermore, it helps you relax without feeling fatigued or tired. Many anti-stress supplements have the problem of making you too sedated.

A 2007 study looked at 12 healthy college students taking a stressful 20-minute math test. One group had 200mg of L-theanine orally before the trial, another group took nothing. People who took L-theanine had all the biomarkers associated with lower stress. Not only that, but the same group experienced a reduction in heart rate.

Social Anxiety

You can also use L-theanine for stress management when you feel a great deal of anxiety in work environments or social situations. One study looked at 20 healthy seniors in a university setting. The students went through a very challenging 10-day pharmacy practice. This exercise involved finishing demanding tasks while being judged for performance.

One group took 200mg tablets of L-theanine twice a day during the study. The second group received a placebo. The group taking L-theanine all reported lower feelings of stress.

On top of that, they had much lower activity from the sympathetic nervous system (SNS). This system is responsible for the “fight or flight” response in threatened animals. In other words, calming the SNS is crucial for maintaining mental acuity in social situations. This result proves that you can safely use L-theanine for social anxiety.

Panic Attacks

Can you use L-theanine for panic attacks? The connection between L-theanine supplements and panic attacks in healthy individuals is unclear. With that said, there are studies which demonstrate theanine’s effectiveness in conditions where panic attacks happen more often.

In one study, schizophrenia patients took a 400mg dose of L-theanine every day for eight weeks. Anxiety levels and feelings of negativity lessened. At the same time, schizophrenic symptoms improved across the board. It appears L-theanine benefits symptoms of anxiety. You may also notice a reduction in panic attacks along the way if you are more prone to them.

2. Improves Sleep Quality

L-theanine for Sleep & Insomnia L-theanine supplements are commonly known as a safe and natural sleep aid for restless people. Many people drink green tea before bed as it helps them relax. But how much L-theanine for sleep do you need?

Research suggests that a 200mg dose of L-theanine before bed improves overall sleep quality. This benefit is entirely possible without inducing sedation or adverse side effects. It is worth noting that L-theanine can also be used during the day to calm down and relax the body and mind. This nootropic does not cause daytime drowsiness, yet you can still be used to improve sleeping habits.

One possible explanation for this is the increased GABA and glycine levels in the brain. These neurotransmitters reduce the effects of excitatory brain chemicals that cause anxiety. As a result, they stop the transmission of negative signals. Simultaneously, the amount of “feel good” signals transmitted by the brain increases. That’s why you can effectively use L-theanine for sleeping better at night.

Fights Insomnia

Currently, few published studies examine the use of L-theanine for insomnia. That has not stopped everyday people from trying it as a solution for a good night’s sleep.

An open-label study looked at middle-aged patients diagnosed with major depressive disorder. A dosage of 250mg of L-theanine was taken each day for eight weeks. As a result, sleep disturbances occurred far less frequently. L-theanine supplements were deemed to be both safe and effective for sleeping through the night. Thus, it may be an excellent natural remedy for your insomnia.

3. Takes the Edge off Caffeine

L-theanine and Caffeine The mental health benefits of L-theanine are significant when you’re trying to clear brain fog. L-theanine can help you feel relaxed without feeling sedated. Therefore, it is often used with caffeine to create smooth and jitter-free energy.

We know that caffeine is a powerful stimulant, but it can have negative side effects. Excessive caffeine can cause jitters, anxiety, restlessness and higher blood pressure. L-theanine helps solve the problems associated with drinking too much coffee.

Combining L-theanine and caffeine helps people feel alert and relaxed. You also won’t experience the energy crash associated with caffeine by itself. Unsurprisingly, both L-theanine and caffeine are present in green tea. There is a miniscule amount of caffeine in green tea. Therefore, it likely won’t keep you up at night unless you’re extremely sensitive to it.

One study had patients consume either 50mg of caffeine or a combination of 50mg caffeine with a 100mg dosage of L-theanine. The study had 27 people completing a series of mentally challenging tasks, twice. The tests were done 60 minutes after ingesting their supplements.

The group taking both an L-theanine supplement with caffeine had superior results. They were far less distracted, they finished tasks faster, and they did so with more accuracy. The group who only took caffeine saw an improvement in either speed or accuracy, but not both at the same time.

Another experiment looked at 24 healthy young adults in a series of cognitive tests. They took 250mg of L-theanine and 150mg of caffeine, either in isolation or combined. The group taking caffeine and L-theanine together reacted faster, and with improved accuracy. They were also more alert and reported lesser feelings of headaches and fatigue. This synergistic effect explains why many of the best smart drugs and nootropics stack caffeine and L-theanine together.

4. May Support Weight Loss

L-theanine for Weight Loss It’s entirely possible that you could use L-theanine for weight loss and be successful with it. One study fed mice L-theanine and various green tea components for 16 weeks. Not only was body weight lowered, but the mice ate less and lost body fat as well. L-theanine did not directly lead to increased fat burning or metabolic output. But, its appetite-suppressing effect led to fewer calories consumed. Theanine can also be used to control stress eating.

Another double-blind clinical trial in 2009 examined how green tea extract affects body composition. The study used 132 subjects ages 21-65 receiving a green tea beverage or a placebo beverage. Triglyceride and free fatty acid levels were lower in the green tea group after just 12 weeks. They also lost more fat around the abdominal area.

It is worth noting that patients exercised during the study. Thus, green tea enhanced the fat loss induced by exercise. We also don’t know how much L-theanine contributed to direct changes in body composition. Still, weight loss appears to be an indirect benefit of L-theanine when paired with exercise.

5. Helps Reduce ADHD Symptoms

L-theanine for ADHD To date, only one double-blind study examined the use of L-theanine for ADHD treatment. Researchers wanted to see if kids with ADHD could improve sleep quality by using L-theanine. One group took 200mg of an oral L-theanine supplement twice a day for six weeks. The other group consumed pills that were placebo.

The boys who consumed L-theanine achieved deeper sleep and spent more time in sleep than the placebo group. L-theanine is well tolerated at the 200mg dosage without any adverse side effects. Thus, you can safely use L-theanine as a natural remedy for ADHD.

The study’s authors admitted that more long-term studies are needed to examine the mental health benefits. With more evidence, we can establish the relationship between L-theanine and ADHD. Many experts in natural medicine recommend a similar dosage of L-theanine for reducing ADHD symptoms. These undesirable symptoms include inattentiveness, hyperactivity, impulsivity, and poor focus. Researchers should also examine females diagnosed with ADHD to confirm their findings.

6. Lessens Feelings of Depression

L-theanine for Depression L-theanine has proven itself as a natural alternative to prescription anti-depressants. This amino acid works by increasing alpha brain wave activity and dopamine levels in the brain. Boosting alpha waves creates a sense of tranquility and relaxation. Increasing dopamine restores the chemical imbalance in the brain. That’s why it’s common for people to use L-theanine for depression.

L-theanine benefits the balance of essential neurotransmitters in the brain responsible for mood stabilization. Depressed individuals are usually deficient in dopamine, which can also lead to more feelings of stress and anxiety. L-theanine does not have the side effect profile of many prescription medications. The lack of adverse reactions makes it a powerful natural remedy for mood disorders.

A literature review examined various doses of L-theanine supplements for increasing alpha-wave activity. In particular, scientists were interested in patients suffering from anxiety and depression.

Using as little as a 50mg dose was enough to create a feeling of relaxation 30 minutes after taking it. However, doses as high as 200mg worked just as well. You would only need 1-2 cups of green tea to feel these anxiolytic effects.

7. Supports Blood Pressure Regulation

L-theanine for Blood Pressure One of the other uses for L-theanine is regulating blood pressure. You can control blood pressure levels by increasing nitric oxide (NO) production. Nitric oxide dilates blood vessels and allows them to function correctly. Higher NO levels can also help lower blood pressure if it is too high. But, how does L-theanine impact nitric oxide levels?

In one study, Indian scientists took cells from the inner surface of blood vessels. After isolating the cells, they exposed them to L-theanine. NO production was enhanced, implying that L-theanine can dilate the arteries. L-theanine can also lower the risk of cardiovascular disease through its effect on blood pressure regulation.

An older study looked at different doses of L-theanine given to hypertensive rats. Doses ranged from 0 to 2000mg/kg. The higher doses led to a significant decrease in blood pressure. It is worth noting that this effect was dose-dependent. The more L-theanine the rats took, the greater the reduction of blood pressure. L-theanine for high blood pressure can be an excellent natural remedy.

8. Enhances Brain Function


L-theanine for Focus You can do more than merely use L-theanine for relaxation. Theanine is also an excellent supplement for focus. L-theanine has received a lot of attention as an agent for enhanced concentration. It is a fundamental component for many effective nootropic stacks.

A systematic review of 11 human studies looked at L-theanine for focus and its effect on the brain and cognitive function. The research suggests people taking L-theanine supplements are better able to switch attention between different tasks. The subjects were also able to pay attention to certain stimuli selectively. These improvements were marginal with L-theanine in isolation. However, L-theanine and caffeine combined greatly enhanced focus and concentration.


Multiple studies have shown the benefits of L-theanine on memory retention. One double-blind study looked at patients with mild cognitive impairment taking a 60mg dosage of L-theanine for 16 weeks.

After 16 weeks, the subjects took a series of psychological tests. Using L-theanine for memory helped patients achieve higher scores in most of the tests. Scores were highest in areas where memory and recall were involved. The increase in results shows that theanine can be a reliable memory booster for those suffering from cognitive impairment. L-theanine can also benefit recall in healthy subjects as well.

L-theanine can also reduce the severity of inflammation in the brain. A 2009 study looked at a neuroinflammatory disease. It is called amyloid-beta-induced neurotoxicity, which is strongly associated with Alzheimer’s disease.

L-theanine was given to infected mice at 4mg/kg for five weeks. The factors responsible for the inflammation were far lower in number. This finding has strong implications for improving memory in patients with cognitive impairment.


Is L-theanine a reliable brain supplement that can help cognition? In 2010, a study involving 44 young adults took either 97mg of L-theanine and 40mg of caffeine or a placebo. They took cognitive performance tests at two different intervals, 20 minutes and 70 minutes. The group taking L-theanine with caffeine was better able to handle challenging tasks. They did so while feeling more alert with less mental fatigue.

Researchers say the health benefits for brain function are easy to explain. People taking L-theanine had an increased ability to focus their attention on the task at hand. For this reason, many nootropic experts use caffeine and L-theanine for cognitive enhancement. It’s a simple, yet highly effective stack.

9. May Help Fight Cancer

L-theanine for Cancer Two Japanese scientists published studies that administered L-theanine alongside doxorubicin to cancer cells. Doxorubicin is an anti-cancer agent designed to halt the growth of cancer cells. In the study, L-theanine enhanced the anti-tumor ability of doxorubicin. L-theanine also reduced the severity of adverse reactions that came from doxorubicin.

However, L-theanine is not proven to prevent cancer directly or in isolation. Studies show that drinking green tea is correlated with a lower risk of getting cancer, but this could be from the antioxidants. For instance, a study conducted in China involved 200 women who had ovarian cancer. Green tea drinkers lived much longer than those who did not. It’s just one of many health benefits of L-theanine and green tea.

10. Enhances Immune System Function

L-theanine for Immune System Can L-theanine supplements boost immune system function and help prevent illness? It turns out, L-theanine can do wonders for making your body more resilient against disease.

A clinical trial of 176 males looked at L-theanine for treating common colds. One group took a 280mg dosage of L-theanine and 700mg of L-cysteine every day for 35 days. The other group received placebo pills. The group taking L-theanine had far fewer occurrences of the common cold.

L-Theanine Side Effects

Side effects of L-theanine are infrequent and small in scope. Some common ones are worth noting. These side effects include possible headaches, dizziness, and gastrointestinal problems. They come from anecdotal reports of users taking L-theanine for improving mental performance.

If your current dosage causes a small adverse reaction, scale it back a bit. If problems increase in severity, you should stop taking L-theanine and consult with your doctor or primary care physician.
Avoid using L-theanine with blood pressure medication. L-theanine can lower blood pressure. Therefore, using medication may reduce it more than what is considered safe. Speak with a physician before using L-theanine alongside your current medications.

L-Theanine Dosage

The dosage for L-theanine will largely vary on its intended purpose. For example, suppose you want to improve your mental performance for a challenging task. WebMD recommends taking an L-theanine dose of 100mg right before the work. Alternatively, combine caffeine with L-theanine at a 2 to 1 ratio. For example, 100mg caffeine to 200mg L-theanine.

Other factors affecting the optimal dosage include bodyweight, mental state, metabolism and more. One study found that 2000mg/kg is the upper limit of L-theanine before you start to experience side effects. To put that L-theanine dosage in context, you would have to drink at least 5 cups of green tea a day to get there.

How long does L-theanine last? Roughly 1-2 hours of relaxation at 50mg is what you can expect. Relaxation is just one of the many uses for L-theanine.

  • For Anxiety: 200-400mg per day. You may go higher for extreme social anxiety, but this is the best dose of L-theanine for anxiety.
  • For Sleep: 100-200mg dosage half an hour before bedtime to prevent insomnia and increase sleep quality.
  • For ADHD: 200mg twice a day. This dosage helps improve focus, attention, and reduces impulsivity.

It is worth noting; there are no definitive dosing guidelines for L-theanine. More research needs to be done to determine the clinical range for each condition it treats. Your tolerance will play a factor in how much you can take. Start with the smallest possible dose and slowly work your way up until reaching the desired effects.

Final Thoughts on the Health Benefits of L-Theanine

L-theanine supplements have become increasingly popular in the world of nootropics. Theanine is not a limitless pill like NZT-48. No such brain booster exists. But you can still expect an improvement in focus and problem-solving skills while using L-theanine and caffeine together. This amino acid also improves your ability to perform when life gets tough. Much of the scientific data out there has shown numerous benefits of L-theanine for your mood and your mental health.

L-theanine is inexpensive and relatively easy to find at any local health food store. You want to aim for products that do not contain additives. Seek out supplements manufactured by a trusted third-party company. Finally, do not use L-theanine supplements, or any dietary supplement, to cover up unhealthy lifestyle habits. You should still strive to exercise each day, eat a healthy diet and get 7-8 hours of deep sleep every night.

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