Green tea has been getting plenty of positive press in recent years. Today, it's touted for its ability to support fat loss, numerous health benefits, and high antioxidant content. But these impressive attributes are only part of the story. There's another reason more and more people are turning to green tea—one that you can feel.

I'm talking about L-theanine, an amino acid found in green tea and almost nowhere else in nature. As an isolated nutrient, L-theanine has recently popped up in several supplements, ranging from nootropics to pre-workout supplements, and for good reason! Recent research suggests that L-theanine can support feelings of calm and focus, and promote productivity.

While this ingredient alone might provide some benefit, it really cashes in and leaves its mark when paired with caffeine. So get a pot of green tea brewing, and let's dive in.

What's So Special About Green Tea And L-Theanine?

L-theanine (referred to as "theanine" here on out) is an amino acid common to the leaves of the plant species Camellia sinensis, the leaf most commonly used to make green tea.1 It's not found in any food, aside from one rare species of mushrooms.


L-theanine is an amino acid common to the leaves of the plant species camellia sinensis, the leaf most commonly used to make green tea. In a number of studies, theanine has been suggested to support focus and concentration.

In a number of studies, theanine has been shown to support focus and concentration without that crazy-intense jittery feeling common in energy drinks. This is where theanine really shines. It has also been shown to support feelings of calmness. Whether at work, studying, or hitting the gym, it's easy to imagine how feeling less stressed and more focused could help you get more done.*

Whether at work, studying, or hitting the gym, it's easy to imagine how feeling less stressed and more focused could help you get more done.

How Does It Work?

Theanine exerts its effects on several fronts, by supporting levels of inhibitory neurotransmitters in the brain and promoting a state of relaxation in the brain.* Here's a breakdown of the main players involved in the process.


GABA (Gamma-aminobutyric acid): Theanine works to support GABA levels in the brain. Increased levels of GABA in the brain promote a relaxation-like effect.[2]

Dopamine: Theanine also supports levels of dopamine in the brain. Dopamine is a hormone that helps control the brain's reward and pleasure centers. An increase in dopamine not only helps with focus, but also promotes feelings of happiness.[*3]

Glycine: Theanine supports glycine, which has similar properties to GABA, and works to further increase dopamine levels.[*3]

Alpha brain waves: Theanine is suggested to have a major impact on alpha-brain-wave activity.1 Alpha-wave generation is associated with an awake, alert, and relaxed state, and might be one of the main reasons theanine is so effective in supporting a healthy stress response.[1]

Increased alpha-brain-wave activity is also linked to alertness and arousal.4 There is research to suggest that the more theanine ingested, the greater the support for alpha-wave activity.[1]

Theanine And Caffeine: Better Together

Theanine may sound like a perfect bedtime supplement, and it's true that it offers some definite benefits when taken at the end of the day. The amino acid has become a common ingredient paired with melatonin in sleep-focused supplements, and many people even take theanine on its own before hitting the hay.

When taking it as a pre-workout during the day, however, there's evidence that theanine is even more effective when taken with caffeine. Theanine and caffeine provide a one-two punch of benefits stronger than taking either alone. Supplementing with both theanine and caffeine has been suggested to narrow focus and enhance attention, which may help to drown out the crowd around you.[5-7]

For lifters, this is invaluable when preparing for, say, a near-maximal weight. A break in form or a forgotten cue can result in a missed attempt—or worse, an injury. Additionally, cosupplementation has been suggested to improve reaction time, which may be beneficial when training for power or speed.[*8]


Supplementing with both theanine and caffeine has been suggested to narrow focus and enhance attention, which may help to drown out the crowd around you.

Not surprisingly, this pairing also shows great promise for cognitive support. A study published in Nutritional Neuroscience had subjects consume 40 milligrams of caffeine and 97 milligrams of theanine shortly before performing a serious of cognitive tests.[9] The experimental group demonstrated increased performance on several cognitive tests and reported reduced tiredness and mental fatigue, as well as increased alertness.[*]

Another study published in Biological Psychology divided subjects into three groups: theanine only, caffeine only, or both theanine and caffeine. Once the supplement was consumed, subjects underwent a series of cognitive tasks 30 and 90 minutes after taking the supplement. The theanine-and-caffeine group demonstrated significant improvements in multiple reaction and information-processing tests.

They also reported feelings of increased alertness, as well as reduced tiredness and less mental fatigue. Benefits were most pronounced in the group that took theanine and caffeine together.[*5]

How To Get Your Theanine

Now that you've learned about the benefits, you're likely wondering how much you should take. Studies examining the effect on theanine have used anywhere from 25-500 milligrams per serving. A 6-ounce glass of green tea provides between 25 and 60 milligrams of theanine in most cases. An ideal pairing for enhanced performance is 200-300 milligrams of theanine with 100-200 milligrams of caffeine.

So how to you get it? You could swap out some of your daily cups of coffee for green tea. Once you get the hang of steeping times—oversteeping produces a bitter flavor—it's easy to get 2-3 strong cups of tea from a single scoop of loose tea or a couple of bags.

You could also buy theanine, which is quite inexpensive on its own, and add it to your pre-workout stack. Yes, theanine has begun popping up in many pre-workout supplements, but not always in efficacious doses. Make sure you're getting enough, and then pair it with enough caffeine to support focus and performance!

  1. Juneja, L.R., Chu, D.C., Okubo, T., Nagato, Y and Yokogoshi H. (1999). L-theanine—a unique amino acid of green tea and its relaxation effect in humansFood Science and Technology, 10<96), 199-204.
  2. Petroff, O.A. (2003). GABA and glutamate in the human brainNeuroscientist, 8(6), 562-573.
  3. Yamada, T., Terashima, T., Okubo, T., Juneja, L.R. & Yokogoshi, H. (2005). Effects of theanine, r-glutamylethylamide, on neurotransmitter release and its relationship with glutamic acid neurotransmission. Nutrition Neuroscience, 8(4), 219-226.
  4. Kelly, S.P. (2006). Increases in alpha oscillatory power reflect an active retinotopic mechanism for distracter suppression during sustained visuospatial attentionJournal of Neurophysiology, 95(6), 3844-3851.
  5. Haskell, C.F., Kennedy, D.O., Wesnes, K.A. & Scholey, A.B. (2005). Cognitive and mood improvements of caffeine in habitual consumers and habitual non-consumers of caffeinePsychopharmacology, 179(4), 813-825.
  6. Heatherley, S.V., Hayward, R.C., Seers, H.E.& Rogers, P.J. (2005). Cognitive and psychomotor performance, mood, and pressor effects of caffeine after 4, 6 and 8 h caffeine abstinencePsychopharmacology, 178(4), 461-470.
  7. Owen, G.N., Parnell, H., De bruin, E.A. and Rycroft, J.A. (2008). The combined effects of L-theanine and caffeine on cognitive performance and moodNutritional Neuroscience, 11(4), 193-198.
  8. Childs, E. & de Wit, H. (2006). Subjective, behavioral, and physiological effects of acute caffeine in light, nondependent caffeine usersPsychopharmacology, 185(4), 514-523.
  9. Giesbrecht, T., Rycroft, J.A., Rowson, M.J. & De Bruin, E.A (2010). The combination of L-theanine and caffeine improves cognitive performance and increases subjective alertnessNutritional Neuroscience, 13(6), 283-290.

About the Author

Paul Salter, MS, RD

Paul Salter, MS, RD

Green tea has been getting plenty of positive press in recent...

View all articles by this author