The Science Behind L Theanine For Sleep

Poor sleep habits can have a dramatic impact upon your quality of life, productivity, and mood. Research has shown that Theanine, a non-protein amino acid derived from plant sources, emits positive effects on sleep and stress. We’re going to discuss the science behind l-theanine in more detail and find out how this powerful sleep aid may get you the eight hours you need.

What Is L-Theanine 

L-theanine is a non-protein amino acid naturally found in tea leaves most notably green tea; non-protein meaning it has the same structure as an amino acid yet is not a building block of proteins. Research indicates that Theanine has anxiolytic (anti-anxiety) effects, which is the precursor to high-quality sleep.

How Does L-Theanine Help Sleep?

Theanine is very unique. Evidence from human electroencephalograph (EEG) studies show that it has a direct effect on brain activity increasing alpha wave frequency which indicates that it relaxes the mind without inducing drowsiness and typical side effects often found with other sleep aids. Anxiolytic properties are also found to produce a soothing and calm effect, which improves sleep latency and duration. 


Theanine inhibits excitatory brain chemicals, creating a sense of calmness and relaxation by boosting levels of GABA, and naturally elevating levels of serotonin and dopamine - collectively known as neurotransmitters. GABA is an inhibitory neurotransmitter, meaning it blocks mental stress, fear, and anxiety establishing a well-balanced emotional/mental state [R]. Neurotransmitters help regulate mood, focus, alertness, as well as appetite. Increased serotonin also converts to melatonin in the brains adrenal glands. Increased serotonin levels ultimately increases melatonin, directly stimulating better sleep.

Enhances Alpha Waves

Alpha brain waves are associated with feelings of wakeful relaxation. Alpha waves are present during REM sleep, enhancing relaxation, reducing stress, and improving sleep quality. Studies have shown that theanine increases alpha brain wave bands, relaxing the mind, without producing drowsiness, thus making theanine a good choice for those that want to reduce anxiety during the day as well, without sedating.  

A study published in the Journal Nutrients, examined the effects of theanine supplementation on stress and cognitive function. 30 healthy participants were administered 200mg per day for four weeks. Study results showed that scores for sleep latency (time to fall asleep), sleep disturbance, and use of sleep medications all reduced after L-theanine administration, compared to the placebo administration [R].

An animal study showed that the combination of GABA and l-theanine had an even greater improvement in time taken to fall asleep, fewer sleep disturbances and an increase in sleep duration than with theanine or GABA alone [R].

L-Theanine Benefits

1. Anxiety And Stress

Theanine is known as an anxiolytic and adaptogen. Adaptogens help your body adapt to stressful situations and reduce anxiety over time. 

A review published in the Journal of Nutrition And Intermediary Metabolism, investigated the effects of theanine on stress and anxiety, and found that of the 104 patients theanine showed significant improvements in reducing stress and anxiety in those experiencing stressful situations [R].

2. Sleep Duration And Quality

Anxiolytic herbs have also been shown to help improve sleep quality, especially sleep latency. Research has shown that when your body is in a relaxed state, sleep quality and the time it takes to fall asleep is positively benefited. 

A study published in Pharmaceutical Biology showed that a mixture of gaba (Gamma- Aminobutyric acid) and l-theanine (100/20mg) showed a decrease in sleep latency (20.7 and 14.9%) and an increase in sleep duration (87.3 and 26.8%) compared to GABA or theanine alone [R]

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Theanine Dosage: How Much Should You Take

A large body of evidence has shown that 200mg of l-theanine administered before bed may support improved sleep quality through the reduction of anxiety [R].

Theanine Side Effects

There are no confirmed side effects of l theanine, taken in relation to sleep. However, when adding a new supplement into your daily routine, it is important to consult a physician or healthcare provider.

Theanine For Sleep: Takeaway

As an anxiolytic, theanine can help produce restful sleep by creating a sense of calmness and relaxation. Elevating neurotransmitter levels such as GABA, serotonin, and dopamine, stimulates the release of melatonin, thus improving sleep quality and duration, in addition to alpha brain waves. If you’re looking for the best sleep supplement, make sure it has at least 200mg of theanine to help you get the rest you need to optimize your well being.

Looking for the best sleep supplement to help you better quality sleep?

Swolverine’s ZMT® maximizes your body’s ability to stimulate muscle growth by promoting high-quality sleep and naturally boosting testosterone levels. ZMT® is made with clinically dosed sleep ingredients such as Melatonin, GABA, Theanine, Tryptophan, Valerian Root, Magnesium Glycinate, and powerful adaptogens like Ashwagandha, Zinc, Rhodiola Rosea, DIM, and Tongkat Ali. ZMT is the perfect nighttime elixir for restful recovery and sleep.


We believe that everyone can optimize not only their athletic performance but their human potential. The way we believe we can optimize performance is through transparency, clinically effective doses, and clinically proven ingredients with evidence-based outcomes. We provide the nutrients you need to power your active lifestyle. 


Rao TP, Ozeki M, Juneja LR. In Search of a Safe Natural Sleep Aid. J Am Coll Nutr. 2015;34(5):436-47. doi: 10.1080/07315724.2014.926153. Epub 2015 Mar 11. PMID: 25759004.

Nobre AC, Rao A, Owen GN. L-theanine, a natural constituent in tea, and its effect on mental state. Asia Pac J Clin Nutr. 2008;17 Suppl 1:167-8. PMID: 18296328.

Hidese S, Ogawa S, Ota M, Ishida I, Yasukawa Z, Ozeki M, Kunugi H. Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial. Nutrients. 2019 Oct 3;11(10):2362. doi: 10.3390/nu11102362. PMID: 31623400; PMCID: PMC6836118.

Kim, Suhyeon et al. “GABA and l-theanine mixture decreases sleep latency and improves NREM sleep.” Pharmaceutical biology vol. 57,1 (2019): 65-73. doi:10.1080/13880209.2018.1557698


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