The Truth About L-Theanine and Sleep (Read Before You Take)

Written by Annalise May
Posted November 13, 2018

Truth About L_Theanine

If you’ve had trouble sleeping lately, you may have been told to drink some tea to help you relax.

It’s time-tested advice, but is there any scientific evidence to support tea’s sleep-enhancing properties?

The answer is...


Tea is a rich source of L-theanine, an amino acid found in tea leaves that promotes calm, focus, relaxation, and — you guessed it — sleep.

L-theanine was first discovered by Japanese scientists back in 1949 and has since been linked to a wide range of potential health benefits.

In addition to promoting sleep and relaxation, L-theanine can help to promote “wakeful relaxation,” improve attention, memory, and learning, and help to maintain a healthy weight.

Whether you like black tea, green tea, or white tea, you will benefit from adding L-theanine to your diet.

How Does L-Theanine Work?


L-theanine is an amino acid.

Amino acids are the building blocks of almost all biological processes in the body. Our muscles, cells, and tissues are all made up of amino acids, each of which carries out an important bodily function.

L-theanine alters specific neural pathways that promote a state of relaxation and induce sleep. Let’s take a look at the specific brain changes that L-theanine promotes:

Boosts levels of calming brain chemicals: Studies on the effects of L-theanine in animals reveal that the compound increases serotonin, dopamine, and GABA levels in the brain.1 An increase in the level of these neurotransmitters is known to improve mood, reduce anxiety, and promote a calm state for a good night’s sleep.

Lowers levels of stress-inducing brain chemicals: At the same time as it increases calming neurotransmitters, L-theanine also reduces the re-uptake of chemicals related to anxiety and stress. Research reveals that the antagonistic effects of L-theanine on stress chemicals promote calmness and improve cognitive function. L-theanine is hypothesized to be a possible cognitive-enhancing and neuroprotective agent, protecting brain cells against stress and age-induced damage.2

Heightens alpha brain waves: The second mechanism through which L-theanine induces a relaxed state is the enhancement of alpha waves in the brain. Research reveals that alpha brain waves, which are typically elevated during mindfulness meditation, are also elevated roughly 40 minutes after ingesting tea leaves with naturally occurring L-theanine.3 These results confirm that L-theanine can significantly mitigate the negative effects of stress and reduce anxiety by affecting brain waves.

Relaxes without sedation: One of the best things about L-theanine is how it is able to induce a relaxed state without sedation. It is unlike typical anti-anxiety drugs. By using L-theanine, you can improve your “wakeful focus” without feeling sleepy during the day. Alpha activity in the brain is hypothesized to play a role in L-theanine’s focus and attention-boosting properties.4

Health Benefits of L-Theanine

Improves Sleep

L-theanine does not act as a sedative, but by reducing stress and anxiety, it induces a restful sleep. Thanks to this boost of relaxation, L-theanine may help to decrease the amount of time it takes to fall asleep.

Do you have a caffeine habit that may be interrupting your sleep cycle? L-theanine has also been studied to counteract the stimulant effects of caffeine. One study in rats reveals that low doses of L-theanine can reverse the effects of caffeine-induced sleep interruptions.5

The naturally occurring L-theanine compound has also shown to be helpful for the sleep health of children. A randomized, double-blind, placebo-controlled study was carried out on a group of 8- to 12-year-old boys diagnosed with attention-deficit/hyperactivity disorder (ADHD). Sleep disturbances are common in children with ADHD, and an estimated 25–50% of kids with ADHD are predicted to meet criteria for a sleep disorder.6

The results of this study revealed that children who took a supplement of L-theanine obtained a significantly longer and more restful sleep than the placebo group. The implications of this research imply that L-theanine is a safe and effective supplement to improve sleep in children with ADHD.

Reduces Anxiety and Stress

L-theanine has long been regarded as an “anxiolytic” or anxiety reducer. Unlike prescription medications, L-theanine is able to induce relaxation without causing sedation. L-theanine has beneficial effects on both the physical symptoms of stress, such as increased blood pressure and high heart rate, and mood.

L-theanine is able to reduce stress in healthy individuals as well as those diagnosed with a clinically significant anxiety disorder. A study completed this year examining the effects of different interventions for anxiety in a psychiatric outpatient unit revealed that L-theanine may be just as effective for treating anxiety as common interventions such as biofeedback and progressive muscle relaxation.7

For the physical symptoms of anxiety, beta-blockers and benzodiazepines are typically a psychiatrist’s first line of defense. These medications work by decreasing blood pressure and reducing the “excitability” of neurotransmitters in the brain. Unfortunately, these medications are not only addictive and meant to be taken on a short-term basis, but they are also sometimes simply not an option for someone suffering from the physical manifestations of anxiety.

L-theanine molecule

Another health benefit of L-theanine is its ability to lower blood pressure by its anti-stress effects on the autonomic nervous system. Research reveals that a supplement of L-theanine significantly changed systolic and diastolic blood pressure in individuals after a stressful mental task when compared to the placebo group.8

Individuals who suffer from dual diagnoses are typically not interested in taking many medications in order to control their symptoms due to interactions between psychiatric medications as well as an increased chance for “brain fog,” fatigue, and sedation.

A study this year examined the effects of L-theanine as an added supplement to antipsychotic therapy in schizophrenia. The results revealed that L-theanine added to existing therapy in those with schizophrenia may be more effective than just antipsychotic therapy for anxiety symptoms.9

Helps to Maintain a Healthy Weight

You may have heard that drinking green tea can benefit weight loss due to its antioxidant and metabolism-boosting properties. It turns out the presence of L-theanine may also help you lose weight. The sleep- and relaxation-inducing effects of L-theanine may be the key to your weight maintenance.

Medical research has established that the increased circulation of cortisol and psychological stress contributes to the risk for obesity and metabolic syndrome.10 Sleep deprivation directly affects your hormones, especially cortisol. When your body does not fully relax at night, you maintain a higher level of cortisol. By shortening the time it takes for you to fall asleep and improving the restfulness of your night, L-theanine along with a healthy diet may help you avoid weight gain.

L-theanine is not only found in tea. It is also identified in some types of mushrooms. L-theanine is understood to be one source of umami flavor. Umami is a type of taste, in addition to sweet, salty, sour, and bitter. It is savory, meaty, and brothy with a long-lasting aftertaste. Research reveals that umami is associated with greater post-meal satiety, resulting in better appetite control and healthy food behaviors in overweight and obese individuals. Try foods with L-theanine — this flavor may help you maintain a healthy weight.

Helps Balance Your Blood Sugar

If you suffer from type 2 diabetes or the effects of high blood sugar, L-theanine may be the supplement for you. Recent research into the ability of L-theanine to modulate the absorption of nutrients reveals exciting results.

A study examining rats implicates that the administration of L-theanine may affect the absorption of glucose by changing the gene expression of the small intestine. This is due to the body’s response to the amino acid. Supplementing the rat’s diet with L-theanine resulted in a decline of insulin secretion as well as glucose levels. L-theanine also reduced the uptake of carbohydrates and fatty acids.11 More research is necessary in humans to see if this result can be replicated.

Mind working

Enhances Attention, Focus, Memory, and Learning

Unfortunately, stress negatively affects the brain and keeps it from functioning at its full capacity. Corticosterone is a hormone released by the body during stressful times. This hormone has been found to prevent some brain activity, including learning and memory formation. Research reveals that L-theanine protects against chronic-stress-induced cognitive impairments in mice.12

L-theanine is also understood to improve cognitive function by boosting memory and focus. One study found that, in individuals with anxiety, the administration of L-theanine improved attention, performance, and reaction time on a cognitive task.13

Other research examining the combination of L-theanine with caffeine establishes an improvement in cognitive skills. A study looking at cognition and mood in healthy individuals found that adding L-theanine to a caffeine regimen improved speed and accuracy in an attention task as well as reduced susceptibility to distraction on a memory test. These results indicate the addition of L-theanine may improve performance in cognitively demanding activities.14

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L-Theanine: What You Need to Know

On top of improving your sleep and your mood, L-theanine may be beneficial for maintaining a healthy weight, improving cognitive abilities, reducing stress and anxiety, and leveling out your blood sugar. Do you think you’re ready to try L-theanine?

Take a look at all the things you need to know about supplementing with L-theanine.

How is L-Theanine Consumed?

L-theanine is typically consumed through tea. The highest levels of L-theanine are in black tea, but it is also present in green tea, white tea, and even mushrooms. Keep in mind that herbal teas do not contain tea leaves and therefore do not contain L-theanine. L-theanine is also present in tea leaves regardless of caffeine content (but don’t forget: caffeine combined with L-theanine is a great cognitive enhancer!). If you’re not a tea drinker, you can also purchase L-theanine in supplement form.

Warm Tea

L-Theanine: Dosage

The proper L-theanine dosage for sleep and stress is between 100 mg and 400 mg.

When you mix it with caffeine, the dosage should be 12–100 mg L-theanine and 30–100 mg caffeine.15

Keep in mind, it is generally recommended that users begin with the lowest suggested dose of L-theanine in order to monitor any reactions. Try gradually increasing your dose until you observe an effect.

Possible Side Effects of L-Theanine

L-theanine has been consumed for centuries for its relaxation and sleep benefits, especially in Japanese traditional medicine. Although it has been around for a long time, the effects of L-theanine at large, daily, therapeutic doses have not been studied extensively in human research.

However, so far, L-theanine has proved to be well tolerated by adults with a healthy lifestyle.

If you suffer from any of the following conditions, you should consult with your doctor before adding L-theanine to your routine:

  • Pregnancy or breast feeding

  • Low blood pressure (hypotension)

  • Dosage in children: Although research has noted therapeutic doses of L-theanine for children, talk to your pediatrician before supplementing your child’s health routine with L-theanine.

  • Interactions with other medications: L-theanine may interact with other medications. These effects could range from increasing sleepiness and drowsiness to interfering with the effectiveness of certain medications. Below is a list of medications that have been scientifically identified to interact negatively with L-theanine:

    • Medications that lower blood pressure (such as beta-blockers and benzodiazepines)

    • Stimulant medications

  • Interactions with other supplements

    • Supplements with caffeine: L-theanine is known to possibly interrupt the stimulating effect of caffeine. These include:

      • Coffee
      • Black tea
      • Guarana
      • Mate
      • Sodas
      • Oolong tea
    • Supplements that lower your blood pressure

      • Casein peptides
      • Cat’s claw
      • Coenzyme Q-10
      • L-arginine
      • Fish oil
      • Andrographis
      • Stinging nettle
      • Lycium16

You don’t have to be a tea drinker to benefit from the amino acid L-theanine. If you find value in any of the health properties of L-theanine, talk to your doctor about supplementing your current health routine with this wonder compound. Sleep well!

To your health,


Annalise May
Contributing Editor, Clear Health Now