What is L-theanine?

Discovered in 1949, L-theanine is an amino acid found primarily in green tea, but also black tea and certain mushrooms. It contributes to the herbaceous, almost grassy (in a good way) taste of green tea, otherwise known as “umami” or savory.

Health benefits of L-theanine

As it relates to sleep, the two primary benefits of L-theanine are that it promotes relaxation without drowsiness and aids in the ability to cope with everyday stress.

Promotes relaxation without drowsiness
Scientific research on the neuropharmacology of L-theanine (1) has shown that it increases the brain's serotonin and dopamine levels, with double-blind, placebo-controlled clinical trials indicating that it increases alpha brain waves (considered an index of relaxation). (2) And while initial research established the effect at higher doses than those typically found in a cup of tea (approximately 20mg), follow-up research confirmed the effect at dietary levels, (3) confirming that “L-theanine...has a significant effect on the general state of mental alertness or arousal.”

Aids in the ability to cope with everyday stress and anxiety
In a study (4) conducted over four weeks, 30 participants received either L-theanine (200 mg/day) or placebo tablets. The results showed that the L-theanine group experienced an improved overall mental state in terms of stress-related ailments and cognitive performance/cognitive function.

It’s impossible to talk about stress without mentioning its implications on sleep. Because when the body reacts to acute (short-term and quickly passing) or psychological stress, there’s an increase in sympathetic nervous system activation. When this occurs, the autonomic nervous system (ANS) releases stress hormones such as adrenaline and cortisol that circulate blood to vital organs and muscles. (5) Heart rate increases, breath quickens, muscles tense, and beads of sweat form as a “fight or flight” response, which evolved as a survival mechanism to allow people to quickly react to life-threatening situations. When this occurs before bedtime, it can run interference with sleep onset (the ability to fall asleep) and sleep maintenance (the ability to stay asleep).

This helps explain why the aforementioned study (4) also had important implications on sleep (latency, disturbance, and the use of medications), as measured by the Pittsburgh Sleep Quality Index (PSQI) scores, which decreased for the L-theanine group by the conclusion of the study. (When it comes to PSQI, a decreased score = better sleep.)

Pittsburg Sleep Quality Index (PSQI) Scores

A 2016 meta analysis (6) with 104 total participants confirmed a link between L-theanine and reduced stress/anxiety in four of the five randomized controlled trials, indicating this ingredient as having anxiolytic, or anxiety-reducing, effects.

READ MORE: How Stress Affects Your Sleep

The synergistic relationship between L-theanine + GABA

Gamma-Aminobutyric acid (aka GABA) is an amino acid produced naturally in the brain. It acts as an inhibitory neurotransmitter that blocks certain brain signals and decreases activity in your nervous system. Glutamate works in reverse as an excitatory neurotransmitter that stimulates nerve cells. Low GABA equals high glutamate, and vice versa.

Studies have shown (7) that the combination of both L-theanine and GABA in supplement form is more beneficial for the quantity and quality of sleep than the individual ingredients alone. Specifically, the mixture can lead to decreases in sleep latency and increases in sleep duration.

The results “demonstrate that the combined use of GABA and L-theanine increase sleep activity to more than a single administration of either amino acid or these synergistic sleep-promoting effects are likely mediated via changes in GABA and/or glutamate receptor expression in the brain,” conclude researchers. (8)

It’s for this reason that Proper’s Sleep + Calm supplement contains both L-theanine and GABA in order to more effectively reduce levels of everyday stress while supporting a restful mind and body.

READ MORE: Guide To The 4 Stages of Sleep (REM Sleep & non-REM Sleep)

Recommended dose of L-theanine

200 mg of L-theanine is considered a clinically beneficial dose.

How to select an L-theanine supplement

In addition to looking for a supplement that contains both GABA and L-theanine, it’s important to remember that because supplements are less strictly regulated by the Food & Drug Administration (FDA), you have to do your research to ensure it contains what it says it does and is not contaminated with heavy metals or pesticides. Here's what to look for:

  • Third-party tested for purity and verified free of heavy metals, microbes, and pesticides
  • U.S. manufactured and produced in an FDA-approved, "Good Manufacturing Practices"-compliant facility
  • Botanical extracts standardized to guarantee consistent purity, potency, and efficacy
  • Free of artificial colors or binders
  • Vegan, gluten/dairy/sugar-free, non-GMO

L-theanine vs melatonin

L-theanine and melatonin are two of the most popular natural sleep aids, so it makes sense why they’re often compared to each other. Here’s what you need to know.

They produce varying effects
While L-theanine provides stress management support by working with GABA to reduce excitability and promote relaxation and calmness, melatonin provides sleep support by directly regulating the sleep-wake cycle. It can improve sleep quality, increase total sleep time, and decrease the amount of time it takes to fall asleep.

Melatonin isn’t for everyone
It should be noted that, for some, melatonin produces symptoms of grogginess, drowsiness, and sleepiness the next morning. If you’re a shift worker or a frequent traveler suffering from jet lag then melatonin might be the best choice for you in order to reset your natural sleep cycle (aka circadian rhythm). If not, you may want to consider other natural dietary supplements such as valerian or GABA.

READ MORE: The Proper Guide To Melatonin: Uses, Types, Side Effects, + More

Safety of L-theanine

Side effects of L-theanine
There are no direct, confirmed side effects of consuming L-theanine in tea or supplement form.

Drug interactions
Because evidence indicates that L-theanine decreases blood pressure, (9) healthcare experts advise against taking it along with high blood pressure medication.

Is it safe to take L-theanine when pregnant?
There is a lack of research on the safety of L-theanine for pregnant/breastfeeding women. We recommend consulting your doctor for more information and personalized medical advisement.