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L-Theanine: Everything You Need To Know About This Plant-Based Powerhouse

Klara Mudge
Functional Medicine Nutritionist
By Klara Mudge
Functional Medicine Nutritionist
Klara Mudge is a nutritionist, health coach and writer trained in functional medicine and neuro-linguistic programming (NLP). She is the creator of Both Sides Buttered, a food and lifestyle blog that covers easy, dull-free wellness.
Ashley Jordan Ferira, Ph.D., RDN
Expert review by
Ashley Jordan Ferira, Ph.D., RDN
mbg Vice President of Scientific Affairs
Ashley Jordan Ferira, Ph.D., RDN is Vice President of Scientific Affairs at mindbodygreen. She received her bachelor's degree in Biological Basis of Behavior from the University of Pennsylvania and Ph.D. in Foods and Nutrition from the University of Georgia.

Have we found and isolated the secret ingredient that gives tea its powerfully calming-yet-focused effect?

L- theanine might be the closest thing we’ve got so far to meditation in a capsule. The traditional therapeutic use of green tea dates back to China 4,700 years ago, and the Japanese regard tea so highly they’ve created a ceremony for it and a separate teahouse in which to serve it.

Thich Nhat Hanh, the Zen master and global spiritual leader, describes tea drinking as a spiritual, meditative act: "Tea is an act complete in its simplicity... This is the act of life, in one pure moment, and in this act, the truth of the world suddenly becomes revealed: all the complexity, pain, drama of life is a pretense, invented in our minds for no good purpose..."

Today, drinking tea still symbolizes psychological calm and contentment for most, and now science is starting to explain the physiological reasons and mechanisms behind these effects. Several scientific publications, including clinical and epidemiological studies, have backed up the health benefits of both black and green teas, with particular focus on L-theanine—a calming amino acid bioactive found to promote alpha-wave brain production (an index of wakeful relaxation similar to that experienced during and directly after meditation).*

Here's all you need to know about nature's powerful relaxant.

What is L-theanine? More than just "umami," it turns out.

L- theanine is a neurologically active organic compound present in the green tea plant (Camellia sinensis, and certain other species of Camellia), the bay bolete mushroom (Boletus badius), and certain nootropics (i.e., dietary supplements that promote cognitive function).* In green tea, L-theanine is the main component responsible for the exotic savory taste of "umami."

Health benefits of L-theanine.

Within around 30 minutes of consumption, L-theanine crosses the blood-brain barrier, where it appears to impact brain waves in diverse and useful ways. Here are six ways that L-theanine promotes cognitive function and supports overall brain health.*


Promotes alpha brain waves.

This powerful phytochemical has a profound impact on oscillatory brain activity (aka brain waves). L-theanine is shown to influence alpha waves1—the same brain bandwidth that promotes relaxation without drowsiness or sedation.*

Alpha brain-wave production also happens during deep meditation, when sensory inputs are minimized and the mind is generally clear of unwanted thoughts or distractions. Interestingly, stimulating alpha waves has also been shown to boost creativity2 and lift mood. Translation? L-theanine's effect on brain activity in the alpha band helps you enter the ideal mental state for, well, most things.*


Supports attention and working memory.

L-theanine not only helps you enter an ideal mental state of relaxation, but helps you further focus on the task at hand by promoting attention and working memory.* Because when you're relaxed and focused, those important things to remember are easier to come by.

In a 2011 study published by the Journal of Functional Foods, healthy college students saw enhanced performance in a visual attention task3 and their reaction time after taking L-theanine supplements. In part, this effect may have to do with L-theanine's impact on working memory (i.e., the amount of information we can mentally hold at any given time).*

In a 2014 Psychopharmacology study, green tea consumption appeared to support performance of working memory by increasing connectivity between frontal and parietal brain regions during working memory processing4.* This is likely because L-theanine has a similar chemical structure to glutamate, which is a neurotransmitter related to memory.


Bolsters cognitive function & brain health now and later.

Because of its antagonistic effects on glutamate receptors and how it affects overall cognition, L-theanine seems to have neuroprotective and cognitive-enhancing abilities.* In a 2011 Pharmacological Research study, green tea powder enriched with L-theanine (i.e., 47.5 milligrams theanine per day) helped enhance cognitive function5 and promote overall brain longevity in older individuals.*


Provides mood support.

By supporting production of the inhibitory relaxing neurotransmitter GABA6, L-theanine plays a key role in mood support.* GABA is important for nervous system function, often used as a targeted supplement to calm anxiousness, promote restful sleep, and bolster overall mood.

L-theanine has also been shown to have a similar boosting effect on dopamine and serotonin levels in the brain in preclinical neurochemistry studies, so more clinical research is warranted.*


Promotes mental resilience.

There are several studies demonstrating how L-theanine supplementation supports resilience to stressors6 and balances out activation of the sympathetic nervous system7. In other words, L-theanine not only helps reduce feelings of anxiousness and promotes stress management in the first place, but it also attenuates the effects of a high-stress response while you're in the midst of it!*


Helps improve sleep quality.

When L-theanine is all about zen focus and mental acuity at lower doses (around 100 milligrams), at higher doses of 200 milligrams and up, L-theanine has been shown to help sleep in a number of ways—including promoting relaxation pre-bedtime8 and delivering that "refreshed" feeling that comes after a good night's sleep, according to a 2015 Journal of the American College of Nutrition review.*

Additionally, thanks to L-theanine's impact on GABA synthesis, the "calm down" signal likely plays a part in these sleep health benefits.*

How to take L-theanine.

L-theanine is present in green, black, and white teas, with green tea containing the most L-theanine (hello, matcha everything!). Green tea contains small amounts of caffeine, plus the added bonus of healthy catechins, polyphenolic antioxidants, and flavonoids (e.g., EGCG) that offer further overall health-protective benefits.

The L-theanine content of tea varies considerably, with estimates around 1 to 2% of the dry weight of leaves and a single cup of tea containing around 25 to 60 milligrams 9of L-theanine. Data indicates that L-theanine at "realistic dietary levels" as low as 50 milligrams has significant mental effects10 (on alertness and cognitive arousal).*

L-theanine is a premium and effective ingredient found in some high-quality nootropic supplements as well, which help promote cognitive function and brain activity in a convenient, targeted delivery format.*

A 2012 study published in The Journal of Nutrition found that L-theanine uptake and metabolism in healthy participants is effective and comparable when provided via capsules or green tea11, so you can leverage the power of this amino acid bioactive in multiple ways! 12

Some ideas to get L-theanine on the regular:

  • High-quality green tea, with or without a squeeze and slice of fresh lemon
  • Green tea blended with MCT oil (Tibetan-inspired butter tea, anyone?)
  • Green iced tea infused with berries, lemon, cucumber, and mint
  • Matcha latte
  • Matcha chia pudding
  • A premium nootropic supplement (with an efficacious L-theanine dose of 50 milligrams or more, preferably in its most researched form, Suntheanine®)

Supplementation, safety, and typical dose.

L-theanine is an amino acid. It is generally safe and well-tolerated by healthy adults, for whom typical doses range between 50 and 400 milligrams.

As always, consult your doctor or integrative or functional medicine practitioner before you begin taking a supplement or make any changes to your existing supplement routine (especially those with blood pressure considerations, as L-theanine can reduce blood pressure). Together, you can go over any possible interactions and find the form and dose that’s best for you, depending on your unique health profile.

When considering a supplement, try to find out as much as you can about the ingredient science, quality, and sourcing as well as bioavailability. Not sure where to start? mindbodygreen's focus+ offers premium sourcing and quality of energy-promoting ingredients at their full-potency, clinically researched doses—including 100 milligrams of L-theanine (as Suntheanine®), instant- and sustained-release caffeine from antioxidant-rich botanicals (i.e., whole coffee fruit and green coffee beans), Panax ginseng, guarana seed extract, and vitamin B12.*

Possible side effects of L-theanine.

L-theanine appears to be remarkably safe with no observed negative effects recorded in human studies so far (and its history of use in tea goes back thousands of years, further bolstering this phytonutrient's welfare).

To inform current clinical research, early preclinical dose-response studies in animals were useful to establish safety limits for intake. In animal research (rodents), L-theanine has been demonstrated to be safe even at very high doses (4,000 milligrams per kilogram of body weight per day was the highest dose tested13).

Nonetheless, it's always a good idea to talk to your health care provider first because everyone's response to foods and supplements are different and depend on individualized factors.

The takeaway.

L-theanine is a dynamic amino acid that promotes a calm state of relaxation and focus (simultaneously!) that can assist you during school, work, or any other cognitively demanding time you may need it.* Whether you choose to harness this bioactive's unique benefits in green tea or supplement form (or both!), its ability to help enhance cognitive function, mental resilience, and mood support is sure to sooth your central nervous system and promote overall well-being.*

If you are pregnant, breastfeeding, or taking medications, consult with your doctor before starting a supplement routine. It is always optimal to consult with a health care provider when considering what supplements are right for you.
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Klara Mudge author page.
Klara Mudge
Functional Medicine Nutritionist

Klara Mudge is a nutritionist, health coach and writer trained in functional medicine and neuro-linguistic programming (NLP). Born and raised in Namibia in Southern Africa, Mudge has lived in Cape Town, London, Luxembourg, and most recently New York she worked as a health coach and director of content at Parsley Health, the functional medicine primary care practice that’s re-inventing modern health care. With a degree in personalized nutrition, she guides clients from all our the world to attainable, sustainable health and writes for a number of leading wellness sites. She is the creator of Both Sides Buttered, a food and lifestyle blog that covers easy, dull-free wellness.