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L-Theanine for Sleep and Anxiety

Medically reviewed by Smita Patel, DO, Susan Kerrigan, MD and Marianne Madsen on January 19, 2023

Breathe in the steaming aroma. Take a calming sip. Feel the coziness start. 


If you’ve ever felt soothing relaxation from a cup of green tea, you have L-theanine to thank. L-theanine, known for its calming properties, is an amino acid found in various types of tea as well as several species of mushrooms. It’s also commonly sold as a supplement.


Many insomnia sufferers swear that a nighttime cup of tea is the only thing that helps them get to sleep, while those living with anxiety often rely on tea to calm their nerves. But are these assertions backed by science? Well, let’s find out.


The benefits of L-theanine


Eastern cultures have held tea in high regard for thousands of years, and like many of their remedies, its medicinal properties have been proven by Western science. The L-theanine in tea has been linked to weight loss, better immune system function, and even increased cognitive performance, but let’s focus on how it can improve sleep and reduce anxiety. 


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Insomnia - Medication

Insomnia - Medication

L-theanine for sleep


A review of multiple studies published in 2015 by the Journal of the American College of Nutrition found L-theanine to be an effective sleep aid. The review noted a Japanese study which found that taking 200 mg of L-theanine 1 hour before bed improved sleep quality in men. 


The same review included a study of postmenopausal elderly women which found that 200 mg of L-theanine led to an “improvement in refreshed awakening, quality of sleep, dream quality, and recovery from exhaustion.”


Lastly, a 10-week study of 93 children with ADHD compared L-theanine to a placebo. 43 subjects were given 200 mg of L-theanine before bed, while 47 received a placebo. The study concluded that L-theanine improved sleep quality significantly in the treatment group, despite the fact that 13 children in the treatment group were taking stimulant medication for their ADHD.


Another 2018 study examined the effects of L-theanine in individuals with anxiety. Interestingly, it found that the amino acid was ineffective at anxiety reduction but effective at improving sleep quality. 


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Insomnia - Steps to a Good Night's Sleep

Insomnia - Steps to a Good Night's Sleep

L-theanine for anxiety


While fewer studies exist on the benefits of L-theanine for anxiety, the existing research is mixed. A 2007 study found that L-theanine resulted in lower stress levels and a slower heart rate in 12 participants, compared to a placebo. However, a 2019 study published in the Journal of Psychiatric Research found L-theanine to be ineffective at reducing anxiety in 46 patients with generalized anxiety disorder. 


While conventional anxiety medications are likely superior to L-theanine, the amino acid can include relaxation and a sense of calm, so it certainly can’t hurt to have a cup of tea if you’re feeling anxious.


So what’s the consensus on L-theanine? The research shows that it can in fact be beneficial for insomnia and may be useful in reducing stress, but likely won’t do much for severe anxiety. Furthermore, L-theanine (and tea in general) is safe to use, so there’s no concern about adverse effects. Of course, if you’re taking any prescribed medication, ask your doctor before stopping your regimen in favor of L-theanine. But feel free to enjoy a cup of tea before bed or when you need to take a break from the stresses of everyday life.


Written by Natan Rosenfeld

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