This Amino Acid Found in Green Tea Might Help You Sleep

Having trouble sleeping is frustrating, affects your quality of life and has a negative impact on your health. Green tea is a rich source of an amino acid that might help.

Like breathing, sleeping seems like the most natural thing in the world. Unbelievably, though, it is estimated that 30% of people in the world struggle with sleep problems.

And those frustrating sleep problems do more than ruin your night and affect your day. They are associated with increased risk of cardiovascular disease, diabetes, depression, Parkinson’s disease and Alzheimer’s disease.

Pharmaceutical sleep aids come with the risk of dependency, side effects and daytime drowsiness. They are also not recommended as a long-term solution. Nature offers many safe, effective sleep aids. One of them might come from green tea.

L-theanine is an amino acid that is found almost uniquely in green tea. It accounts for almost 50% of all amino acids in green tea and makes up about 1-2% of its weight. It crosses the blood-brain barrier and affects a number of neurotransmitters that influence sleep and relaxation, including serotonin, dopamine and GABA.

For the first time, a meta-analysis has looked at L-theanine’s effect on sleep. It included 18 controlled studies. In 11 of the studies, L-theanine was combined with other ingredients, and in 8 of them, the L-theanine was alone. It would have been nice to see just how the L-theanine did on its own.

The results showed that L-theanine significantly improved subjective measures of sleep, including how fast people fell asleep, daytime dysfunction, and, most importantly, overall sleep quality.

There was a great variation in the studies, including the dose of L-theanine and the length of time it was given. Several objective measures became significant when just one of the studies was removed, including time to fall asleep and sleep efficiency.

L-theanine was safe, with no significant difference in side-effects between L-theanine and placebo.

A few things need to be noted about this study. Most of the studies were done on people who did not have sleep problems, meaning there was not much room for improvement. L-theanine may perform even better on people who actually struggle with insomnia.

Also, the question asked by the study may need tweaking. L-theanine improves calm by increasing alpha brain waves, which leads to relaxation and better focus, and deceasing beta brain waves, which reduces nervousness, hyperactivity and unfocussed thoughts. Its specialty may not be putting you to sleep as much as improving your sleep.

Sleep Medicine Reviews. June 2025;81:102076.

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For much more on preventing and treating insomnia, see our book The Family Naturopathic Encyclopedia.

For comprehensive natural help with your health, including insomnia, make an appointment to see Linda Woolven now. Linda’s clinic is now open for in person and virtual appointments.

The Natural Path is intended for educational purposes only and is in no way intended for self-diagnosis or self-treatment. For health problems, consult a qualified health practitioner for a comprehensive program.

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