What is L-theanine? Here’s everything you need to know!

✓ Expert Review by: 
Derek Timm, PhD, RDN

L-theanine is a unique amino acid found naturally in tea leaves, particularly green tea. It is the key component of tea that provides relaxation. For centuries, it’s been revered for its ability to boost brain function and promote a relaxed, yet alert state.

Whether you’re feeling stressed, finding it difficult to stay focused or having trouble falling asleep at night, you may be considering L-theanine as a solution. Keep reading to learn more about this unique amino acid.

What is L-Theanine?

How does L-Theanine work?

L-theanine, the common form of theanine, works by stimulating activity in the brain known as alpha waves. When you’re wide awake and relaxed, you’re probably producing more alpha brain waves. This calm, alert state is associated with better focus. Alpha waves help you stay in the moment (also referred to as “in the zone”). It’s a sought-after state of consciousness in this overstressed world.

L-theanine can also promote GABA, another calming brain chemical, and increases dopamine release through modulation of glycine and AMPA receptors.

Learn about the benefits of pure l-theanine in this short video

What are the sources of L-theanine?

L-theanine is generally consumed naturally in green tea, one of nature’s most abundant sources of this natural amino acid. Lesser amounts are found in black tea and white tea, as well as some types of mushrooms.

While enjoying a cup of tea may be relaxing, it is difficult to obtain significant amounts of L-theanine by drinking green tea alone. Most of the benefits of L-theanine are experienced with doses between 50 and 250 mg while the typical green tea sold in North America contains less than 10 mg of L-theanine per serving.

This is why some people prefer to consume L-theanine in the form of a dietary supplement.

Can you take L-theanine every night?

Yes, L-theanine can be safely consumed on a daily basis. It’s recommended to take L-theanine about 30-60 minutes before you want to fall asleep.

What are the benefits of L-theanine?

Human clinical research has shown that L-theanine promotes relaxation and may help to improve sleep quality. Additional studies suggest that L-theanine may help to heighten mental acuity, promote focus and concentration, and reduce some of the negative side effects of caffeine.*

L-theanine for better sleep

Consuming L-theanine about an hour before bedtime helps quiet and soothe your racing mind so you can fall asleep more easily. It promotes a deep, regenerative sleep which may help you feel refreshed and rejuvenated in the morning.

L-theanine for stress reduction

When you’re feeling frazzled, consuming L-theanine may help to ease tension and promote a relaxed yet highly alert state. Plus, because L-theanine is non-sedating, you can take it during the day without worrying about it making you feel drowsy.

L-theanine for sharper focus

The benefits of consuming L-theanine during the day include helping to improve focus, attention and mental clarity. A study published in the Journal of Functional Foods found that L-theanine improved reaction time and attention in normal, healthy university students.

L-theanine for cognitive performance

Consuming L-theanine may help improve accuracy and concentration, making it ideal for multi-taskers and students. Research has shown that adding a form of L-theanine to caffeine improves reaction time, which gamers and sport enthusiasts find especially attractive. Studies have also shown that L-theanine may round out the jitters and other negative effects typically associated with caffeine.

L-theanine may also enhance your mood

Research shows that L-theanine may help people who are dealing with everyday stressors to feel more positive.

5 benefits of l-theanine

Is L-theanine safe?

The good thing about L-theanine is that this compound has been consumed for thousands of years as a natural component of green tea, so it really has a long safety history. Moreover, more than 200 research studies have examined L-theanine and found no major side effects.

What is the proper L-theanine dosage?

Based on the results of clinical studies, start with 50 to 200 mg of L-theanine, with or without food. If you’re experiencing higher levels of stress, consider taking 200 mg for better results. The benefits will typically kick in within 30-60 minutes and can last up to 8 hours.

Can children take l-theanine?

Yes, L-theanine is suitable for use by children ages two years and older. Consult with your child’s pediatrician if you have any questions.

Best L-theanine Supplements

There are many L-theanine supplements available today. To help narrow your search, you’re smart to do your research on the main ingredient. Consider such factors as the L-theanine’s purity and whether that specific form has been scientifically studied for its intended benefits.

Suntheanine, a patented pure form of L-theanine, has a long history of safety and clinical research. Most of this research has used the gold standard for testing: randomized, double blind and placebo-controlled trials. This has resulted in a solid body of science demonstrating that Suntheanine safely supports sleep, stress reduction and cognitive function.

What is Suntheanine?

Suntheanine is produced via a patented process that mimics the natural process in green tea leaves, resulting in a 100% pure L-isomer-theanine. Its safety and efficacy are substantiated by more than 40 human clinical trials. This research suggests that 50 mg to 200 mg of Suntheanine safely stimulates alpha brain waves. Unlike other stress-reducing supplements, Suntheanine doesn’t cause drowsiness so you can take it any time of day.

Suntheanine is Non-GMO Project Verified, Kosher, Halal and Informed Ingredient certified.

Recent L-theanine research

Suntheanine is one of the most well-studied forms of L-theanine on the market, in part because researchers prefer its purity and its consistency from one batch to the next. Below are some recent l-theanine studies performed using Suntheanine.

Effects of l-Theanine on Cognitive Function in Middle-Aged and Older Subjects: A Randomized Placebo-Controlled Study

Author: Baba, et al Location: J Med Food. 2021 Apr;24(4):333-341. Read ...

The effect of L-theanine incorporated in a functional food product (mango sorbet) on physiological responses in healthy males: a pilot randomized controlled trial

Author: Williams, J. Publication: Foods (Basel, Switzerland) 2020 ...

Effects of L-theanine-caffeine combination on sustained attention and inhibitory control among children with ADHD: a proof of concept neuroimaging RCT

Author: Kahathuduwa, C. Publication: Scientific Reports 2020 Aug Read ...

Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial

Author: Hidese, S. Publication: Nutrients 2019 Oct Read Full ...

Effect of L-theanine tablets in reducing stress-related emotional signs in cats: an open-label field study

Author: DRAMARD, V. Publication: Irish Veterinary Journal 2018 ...

The effect of L-theanine supplementation on the immune system of athletes exposed to strenuous physical exercise

Author: Juszkiewicz, A. Publication: Journal of the International Society of ...

Effects of chronic l-theanine administration in patients with major depressive disorder: an open-label study.

Author: Hideese, S / Ota, M / Wakabayashi, C / Noda, T / Okubo, T / Kunugi, ...

In search of a safe calming sleep aid.

Author: Rao, T.P Publication: Journal of the American College of Nutrition. March, 16, ...

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Final thoughts about L-theanine

Found abundantly in green tea, L-theanine is an amino acid used for centuries to promote calm and relaxation. For decades, many people have consumed L-theanine supplements for help improving sleep quality.

A significant body of scientific research also verifies that L-theanine’s effects may also include enhanced focus and concentration, mental clarity and cognitive performance.

L-theanine is not a stimulant. Nor will it cause next-day drowsiness. When combined with caffeine, L-theanine has been shown to smooth the jitters and other negative effects associated with caffeine.

L-theanine is considered safe to consume regularly. However, it is recommended to choose the purest form of this ingredient. Suntheanine is produced via an enzymatic fermentation process that mimics the natural process in green tea leaves resulting in a 100% pure L-isomer-theanine.