L-theanine is an amino acid predominantly found in tea leaves, particularly in green tea. It’s well known for its range of health benefits and has gained notoriety in the health conscious community for its ability to enhance mental focus, reduce stress, and improve sleep quality.

Read on to learn more about what L-theanine is, its benefits and the best natural sources where you can find this powerful amino acid! 

Understanding L-theanine

L-theanine is a non-protein amino acid which means it doesn't contribute to building proteins in the body like other amino acids such as lysine or tryptophan. 

Instead, L-theanine works by influencing brain functions, primarily by increasing the production of certain neurotransmitters like gamma-aminobutyric acid (GABA), serotonin, and dopamine. These neurotransmitters play a crucial role in mood regulation, sleep, and relaxation.

One of the most interesting things about L-theanine is its ability to cross the blood-brain barrier, allowing it to have direct effects on the central nervous system. When consumed, L-theanine has been shown to increase alpha brain wave activity, which is linked to a state of relaxed alertness. This unique effect makes L-theanine particularly valuable for anyone seeking to reduce stress and anxiety without the sedative effects that often accompany other “calming” supplements.

What are the best natural sources of L-theanine?

Green tea 

Green tea is the most well-known and concentrated natural source of L-theanine. The tea leaves contain a significant amount of L-theanine, especially when grown in the shade - as is the case with high-quality matcha green tea! In addition to L-theanine, green tea provides a ton of other beneficial compounds, including antioxidants like catechins, which offer even more health benefits like improved metabolism, reduced inflammation and cancer fighting properties. 

Matcha

Matcha, a type of powdered green tea, is an even richer source of L-theanine than regular green tea. There’s more L-theanine in high-quality matcha because matcha is made from tea leaves that are grown in the shade, which increases the L-theanine content and when you consume matcha, you ingest the entire tea leaf, resulting in a higher intake of L-theanine compared to steeped green tea. 

Black tea

While not as high in L-theanine as green tea, black tea still contains a reasonable amount of this L-theanine. The fermentation process that black tea undergoes reduces its L-theanine content.

White tea

White tea, like green and black teas, also contains L-theanine, though in even lower amounts. The minimal processing of white tea helps preserve many of its natural compounds, making it a good, but mild, source of L-theanine.

Others

Although tea is the most concentrated and accessible source of L-theanine, small amounts can also be found in certain mushrooms, particularly the bay bolete (Boletus Badius). 

5 health benefits of L-theanine, according to the latest research

Stress reduction and relaxation 

L-theanine is best known for its calming effects. By increasing the levels of GABA and serotonin in the brain, L-theanine helps promote relaxation and reduce stress. Studies show that people who consume L-theanine experience a significant reduction in their stress response, making it easier for them to remain calm in high pressure situations. 

Improved focus and cognitive performance

L-theanine also enhances mental focus. This dual action of promoting relaxation while improving focus makes it really unique. When combined with caffeine (which is also found in tea)  L-theanine can enhance cognitive performance, particularly in tasks requiring sustained attention and focus. This combination is one reason why green tea, which naturally contains both L-theanine and caffeine, is often preferred by people who need to stay alert without the jitteriness that coffee can cause.

Better sleep quality

L-theanine won’t directly put you to sleep like melatonin, but it can improve sleep quality by reducing anxiety and promoting relaxation. It helps the mind to relax without the grogginess associated with other sleep aids, making it easier to fall asleep naturally. Plus, if all of your daily caffeine sources contain L-theanine, you won’t be fighting jitters and anxiety during the day or before bed. That can greatly improve how fast you fall asleep, how long you stay asleep and how clear you feel when you wake up. 

Supporting your immune system

Research suggests that L-theanine supports the immune system by helping the body fight off infections more effectively. This is particularly important during times of high stress when your immune system is likely working on overdrive and is compromised. Regularly consuming L-theanine, particularly from natural sources like green tea, can contribute to your overall immune health.

Cardiovascular health

L-theanine can help to lower blood pressure and improve heart health. Its ability to reduce stress and promote relaxation could indirectly contribute to a healthier heart by consistently reducing the burden on your cardiovascular system.

The bottom line

L-theanine is a unique amino acid. Its ability to cross the blood-brain barrier and directly influence neurotransmitter activity makes it a massively valuable natural compound for mental and physical well-being. While matcha is the best natural source of L-theanine, other teas such as green, black and white tea do have L-theanine in them. Regularly consuming l-theanine can help promote a healthier, more relaxed lifestyle. 

Sources:

Li, M. Y., Liu, H. Y., Wu, D. T., Kenaan, A., Geng, F., Li, H. B., Gunaratne, A., Li, H., & Gan, R. Y. (2022). L-Theanine: A Unique Functional Amino Acid in Tea (Camellia sinensis L.) With Multiple Health Benefits and Food Applications. Frontiers in nutrition, 9, 853846. https://doi.org/10.3389/fnut.2022.853846

Juneja, L. R., Chu, D.-C., Okubo, T., Nagato, Y., & Yokogoshi, H. (1999). L-theanine – A unique amino acid of green tea and its relaxation effect in humans. Trends in Food Science & Technology, 10(6-7), 199-204. https://doi.org/10.1016/S0924-2244(99)00044-8

Unno, K., Noda, S., Kawasaki, Y., & Yamada, H. (2019). Mechanisms underlying the effect of L-theanine on mental stress-induced brain activity: An fMRI study. Nutrients, 11(10), 2362. https://doi.org/10.3390/nu11102362

Kimura, K., Ozeki, M., Juneja, L. R., & Ohira, H. (2007). L-theanine reduces psychological and physiological stress responses. Biological Psychology, 74(1), 39-45. https://doi.org/10.1016/j.biopsycho.2006.06.006