L-theanine: Why Drinking Green Tea is Relaxing

Did you know that only the tea plant (Camellia sinensis) and a few others contain L-theanine?

The characteristic flavor of green tea is due in large part to this particular compound. If you’re a green tea lover like me, you’ll definitely want to learn all about L-theanine.

What is L-theanine?

Green tea leaves contain many different amino acids. Amino acids are molecules containing an amine group(NH3), a carboxylic acid group(R-C=O-OH) and a side-chain that varies between different amino acids. They are the building blocks of proteins, although some of them don’t form any proteins.

When green tea is brewed, only the water-soluble amino acids become relevant. L-theanine makes up to 60% of that amino acid content. Its molecular formula is C7H14N2O3, it is also known as 5-N-ethyl-glutamine, and it’s a non protein-forming amino acid.

L-theanine is important because it adds to the umami flavor (tastiness) and sweetness of green tea.

What makes L-theanine so special?

So what else does L-theanine do besides providing flavor?

The main benefit of L-theanine is that it increases alpha brain wave activity, which induces relaxation. By relaxing you are effectively able to reduce stress!

On top of that, it combines with caffeine in a matter that produces relaxed alertness. L-theanine lets you enjoy the increased-concentration effect from caffeine (also found in green tea) without the associated anxiety and restlessness.

L-theanine was approved by The Japanese Ministry of Health and Welfare for universal consumption in 1964, while in the US the FDA approved its use as a dietary supplement.

L-theanine content in green tea

Gyokuro is known for having a high amount of L-theanine. Do you know why? L-theanine is slowly converted into catechins due to photosynthesis.

Because gyokuro cultivation involves shading the tea plant, less photosynthesis occurs so that more L-theanine is left on the leaves. In fact, L-theanine gives gyokuro its characteristic sweetness and balanced flavor.

Younger leaves have more L-theanine than older ones, while later harvests have each less L-theanine. Shaded teas like gyokuro, kabusecha and matcha are a good source of L-theanine. Also look for teas made from the first harvest.

There are more benefits of L-theanine, which I will be sharing with you on a later post about the health benefits of green tea. Meanwhile, relax with your favorite type of Japanese green tea with the help of L-theanine.


Asia Pacific Journal of Clinical Nutrition; L-theanine Reduces Psychological and Physiological Stress Responses; A.C. Nobre et al.; 2008
The combination of L-theanine and caffeine improves cognitive performance and increases subjective alertness>; Nutritional Neuroscience 13.6 (2010): 283-90

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16 Responses to L-theanine: Why Drinking Green Tea is Relaxing

  1. Catalina Perez A says:

    Si total la L-teanina una vez ingerida es liberada al torrente sanguineo,y se dirige al cerebro,donde estimula las ondas cerebrales … las cuales son impulsos electricos que tienen correlacion con distintos tipos de estados mentales y animicos … hay cuatro categorias de Ondas cerebrales:
    Alfa : presentes especialmente durante los estados de alerta relajada .
    Beta : presentes durante las situaciones ligeramente estresantes o emocionantes.
    Delta : Estan presentes durante la etapa mas profunda del sueño.
    Theta : Presentes especialmente durante el sueño ligero y la somnolencia .

    • Hello Catalina
      I didn’t know about the other 3 waves.
      I speak Spanish too, but since this blog is written in English, I prefer comments written in that language so that everyone can understand.
      Thank you for your comment!

  2. Terry Morrison says:

    Nice article. However, I don’t believe L Theanine can be both a source of umami and sweetness. For one thing umami comes from glutamate (as in msg) which is a protein forming amino acid, whereas, as you pointed out, L Theanine is a non protein forming amino acid.

    • Hello Terry, thanks for your comment.
      L-theanine is not a direct source of umami, but apparently its presence amplifies the intensity of umami flavor, originally due to the glutamate (also present in tea leaves).
      Here’s a study for you to look at: http://www.aseanfood.info/Articles/11016318.pdf
      It’s also mentioned on page 29 of the Nihoncha Instructor Association book: 日本茶のすべてがわかる本.

      • Terry Morrison says:

        Thank you for the reference Richard. It has been very helpful. I have referred it to other tea aficionados (along with the link to your blog). I have one other question. A person recently told me that L Theanine is created in the roots and delivered to the rest of the plant via the roots and vascular system. He maintains the highest concentration is in the roots and diminishes as you go further away from the roots, with the leaves having the least L Theanine content. Have you ever heard of this?

        • Hi Terry, thanks for the referral : )
          Yes, L-theanine is produced in the roots (see my post about gyokuro in the “Types of Japanese green tea” tab), but when it gets to the leaves it’s converted into catechins via photosynthesis, that’s why gyokuro must be shaded to preserve the L-theanine.
          I’ve never heard of people consuming the roots of the tea plant for the L-theanine content, though.

  3. Angie Munoz says:


    Very interesting this article.

    Thanks Ricardo.

  4. Chris Jarrell says:

    I’m so happy to have found your blog Ricardo. I’ve recently become obsessed with tea, particularly green teas. 🙂 I drink many cups of Houjicha as well as Chinese Gunpowder throughout the day while I continue to explore the many other styles available.

    One thing I’ve noticed since basically giving up coffee is that tea has such a well-balanced effect…both mental alertness and also a sense of well being and relaxation. Truly a great beverage as well as medicine for those like me who suffer from anxiety and depression.

    Thanks again for sharing all this helpful info on Japanese tea 🙂 I have yet to try many of the varieties and am looking forward to years of tea enjoyment.

  5. Sasha says:

    Hello everyone!

    I have a question.

    I am all about L-Theanine …. and I wonder … since Match has around 50mg per serving … how much does Gyokuro has per 5g of leafs?

    Thanks in advance

    • Hi Sasha

      The content of matcha and gyuokuro should be very similar, because their cultivation process is practically the same.

      However, since gyokuro is a loose leaf tea, you have to make multiple infusions or basically eat the tea leaves to get the full L-theanine content, while in matcha you are ingesting it all.

  6. Maria Alberto says:

    I ditched coffee for matcha tea. Matcha tea, if done right, it’s deliciuos and extremely relaxing for me; I drink it before bedtime and I sleep better.

  7. Ana B. says:

    Hello Ricardo
    Nice blog.
    My question goes in direction if kukicha tea contains theine (teina), as everyone says is theine and caffeine free and I cannot sleep if i drink at night.

    • Dear Ana

      I quote from Wikipedia: “In 1827, M. Oudry isolated “théine” from tea, but it was later proved by Mulder and by Carl Jobst that theine was actually caffeine.”

      There is no theine, just caffeine. But kukicha isn’t very high in it. Also, L-theanine is relaxing, so the effect is not the same.

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