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

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).*

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.*

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).*

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.

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.*

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

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.

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).