What You Need to Know About L-theanine

Sleep better at night, feel relaxed during the day.

Michael J. Breus Ph.D.

Sleep Newzzz

Posted August 29, 2017 |  Reviewed by Lybi Ma


I often encourage my patients to drink tea. Black tea is a lower-caffeine alternative to coffee during the day, and decaffeinated tea can be a calming part of a nighttime power-down ritual before bed. Whatever time of day or night, drinking a cup of tea can be a soothing, relaxing ritual. I often drink tea myself—my favorite is my personal recipe for banana tea.

In addition to its calming qualities, tea also contains compounds that deliver some real health benefits. One of those compounds: L-theanine.

Fortunately, you can also get L-theanine in supplement form, which can help with relaxation, focus, and sleep. Let’s take a closer look at L-theanine and its calming, centering, sleep-boosting abilities.

What is L-theanine?

L-theanine is an amino acid that is found in tea leaves. It was identified in tea by Japanese scientists in 1949. While tea is the most common dietary source for L-theanine, this compound is also found in some types of mushrooms. In foods, particularly green tea, L-theanine is thought to be a source of umami, the savory, brothy taste.

Scientists studying umami flavor have made some interesting discoveries. Umami has been linked to decreased risk for obesity. It may stimulate metabolism, and may boost sensations of fullness and lengthen the time before hunger returns after eating.

There’s also evidence suggesting that L-theanine, when consumed in tea, may change taste perception, specifically diminishing the taste of bitterness in foods such as chocolate and grapefruit.

How L-theanine Works

L-theanine promotes relaxation and facilitates sleep by contributing to a number of changes in the brain:

  • Boosts levels of GABA and other calming brain chemicals. L-theanine elevates levels of GABA, as well as serotonin and dopamine. These chemicals are known as neurotransmitters, and they work in the brain to regulate emotions, mood, concentration, alertness, and sleep, as well as appetite, energy, and other cognitive skills. Increasing levels of these calming brain chemicals promotes relaxation and can help with sleep.
  • Lowers levels of “excitatory” brain chemicals. At the same time it is increasing chemicals that promote feelings of calm, L-theanine also reduces levels of chemicals in the brain that are linked to stress and anxiety. This may also be a way that L-theanine can protect brain cells against stress and age-related damage.
  • Enhances alpha brain waves. Alpha brain waves are associated with a state of “wakeful relaxation.” 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, 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.

Benefits of L-theanine

Improving sleep. With its ability to increase relaxation and lower stress, L-theanine can help in sleep in a number of ways. L-theanine may help people fall asleep more quickly and easily at bedtime, thanks to the relaxation boost it delivers. Research also shows L-theanine can improve the quality of sleep—not by acting as a sedative, but by lowering anxiety and promoting relaxation.article continues after advertisementhttps://74f7890a179baa0ce2782495f836b7d6.safeframe.googlesyndication.com/safeframe/1-0-38/html/container.html

There’s evidence that L-theanine may help improve sleep quality in children with attention deficit hyperactivity disorder (ADHD). A study examined the effects on the sleep of boys ages 8-12, and found that the supplement worked safely and effectively to improve the quality of their sleep, helping them to sleep more soundly.

Reducing stress and anxiety. L-theanine is what’s known as an anxiolytic—it works to reduce anxiety. Some anxiolytics, such as valerian and hops, have sedative effects. L-theanine, on the other hand, promotes relaxation and stress reduction without sedating. L-theanine can help foster a state of calm, attentive wakefulness.

L-theanine has positive effects on both the mental and physical symptoms of stress, including lowering heart rate and blood pressure.

Research suggests that L-theanine can help reduce anxiety in people with schizophrenia and schizoaffective disorder.

Enhancing attention, focus, memory and learning. Under stress, the body increases production of certain hormones, including cortisol and corticosterone. These hormone changes inhibit some brain activity, including memory formation and spatial learning. L-theanine helps to lower levels of the stress hormone corticosterone, and avoid the interference with memory and learning.

L-theanine may help boost other cognitive skills. Research shows L-theanine can increase attention span and reaction time in people who are prone to anxiety. It may help improve accuracy—one study shows that taking L-theanine reduced the number of errors made in a test of attention.

Sometimes, L-theanine is used with caffeine to enhance cognitive skills. Studies show that combinations of L-theanine and caffeine can improve attention span, enhance the ability to process visual information, and increase accuracy when switching from one task to another.article continues after advertisementhttps://74f7890a179baa0ce2782495f836b7d6.safeframe.googlesyndication.com/safeframe/1-0-38/html/container.html

Helping maintain a healthy weight. The anti-anxiety and sleep-promoting abilities of L-theanine may help people to maintain a healthy weight. After all, getting enough sleep and limiting stress are both key to sticking with a healthy diet and avoiding weight gain.

L-theanine may also play a more direct role in weight maintenance. There’s scientific evidence indicating L-theanine may help to limit fat accumulation and weight gain, and pay help to protect against obesity.

What to Know

Always consult your doctor before you begin taking a supplement or make any changes to your existing medication and supplement routine. This is not medical advice, but it is information you can use as a conversation-starter with your physician at your next appointment.


The following doses are based on amounts that have been investigated in scientific studies. In general, it is recommended that users begin with the smallest suggested dose, and gradually increase until it has an effect.

  • For sleep, stress and other uses: 100 mg to 400 mg
  • In combination with caffeine: 12-100 mg L-theanine, 30-100 mg caffeine

Possible Side Effects

L-theanine is generally well tolerated by healthy adults.

People in these groups should consult with a physician before using an L-theanine supplement:

  • Pregnant women and those who are breastfeeding.
  • Individuals with low blood pressure. L-theanine may lower blood pressure. If you have low blood pressure, speak with your doctor before beginning to use L-theanine.
  • Children. Consult your child’s physician before beginning their use of L-theanine.

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The following medications and other supplements may interact with L-theanine. Effects may include increasing or decreasing sleepiness and drowsiness, interfering with the effectiveness of the medications or supplements, and interfering with the condition that is being treated by the medication or supplement. These are lists of commonly used medications and supplements that have scientifically identified interactions with L-theanine. People who take these or any other medications and supplements should consult with a physician before beginning to use L-theanine.

Interactions with medications

  • Medications used to treat high blood pressure
  • Stimulant medications

Interactions with other supplements

Supplements that contain caffeine. L-theanine may interrupt the stimulating effects of caffeine and herbs or supplements that contain caffeine. Some of these include:

  • Coffee
  • Black tea
  • Oolong tea
  • Guarana
  • Mate
  • Cola

Supplements that lower blood pressure. L-theanine may lower blood pressure, and combining this supplement with other blood-pressure lowering supplements may cause blood pressure to drop too much. Some of these include:

  • Andographis
  • Casein peptides
  • Cat’s claw
  • Coenzyme Q-10
  • Fish oil
  • L-arginine
  • Lycium
  • Stinging nettle

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People have relied on the stress-relieving, sleep-promoting powers of L-theanine for centuries, by drinking tea—especially green tea. You don’t have to be a tea drinker to benefit from the soothing properties of this ancient herb—and even if you already enjoy a regular cup of tea, you may find an L-theanine supplement helps with relaxation, stress, and sleep.

Sweet Dreams,

Michael J. Breus, PhD
The Sleep Doctor™


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About the Author

Michael J. Breus, Ph.D., is a clinical psychologist and a diplomate of the American Board of Sleep Medicine. He is the author of Beauty Sleep.


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