L-Theanine Tea - Everything You Should Know

L-Theanine Tea - Everything You Should Know

March 29, 2022

L-Theanine Tea - Everything You Should Know

At Zest, we're always talking about the two key features of our energy tea - caffeine and L-Theanine. We all know what caffeine does, but what about L-Theanine? This unique amino acid has some very intriguing properties that are part of the reason tea is better than coffee. Fact.

In this short guide, we'll give you a quick and easy explanation of L-Theanine and take you through some of the potential health benefits we can draw from the numerous studies conducted.

To get a taste of drinking tea with high levels of green tea catechins, caffeine, and L-Theanine, jump straight to our energy tea selection.

PLANT POWERED ENERGY DRINKS  We get it - you can't function before caffeine hits your bloodstream. Good thing Zest has more caffeine than coffee, plus your stomach won't hate you for drinking it.   ENERGY: 150 mg caffeine - more than coffee FOCUS: L-Theanine for all-day, steady alertness HEALTH: Low to no surgar, and made with completely natural ingredients  SEE PRODUCT PAGE 



L-Theanine is an amino acid which is one of several organic compounds found in the leaves harvested from tea plants. Along with epigallocatechin gallate (EGCG), it is a well-known natural constituent that has a positive impact on the human body. Numerous EEG studies have shown that it has a direct effect on the brain in particular.1

There are many plants that produce amino acids that we need in our diet, however the Camellia sinensis tea plant is the only one that creates L-Theanine. A typical cup of black tea could contain around 20mg of L-Theanine - but it can vary wildly between tea types, plant cultivars, and of course, how you prepare the tea.

You can also take L-Theanine in supplement form and many of the studies listed below will use high concentrations of L-Theanine extract instead of giving participants cup after cup of tea to consume. Taking L-Theanine in supplement form is certainly easier, but you won't benefit from the other nutrients in tea - caffeine, EGCG, and other catechins.

This makes better L-Theanine for scientific studies, but if you are looking to get a more rounded array of health benefits then consuming tea is a better choice. In fact, several studies have found that the effects of L-Theanine alone are not as great compared to the combination of L-Theanine and caffeine together.2


L-Theanine and Caffeine

white gaiwan filled with green tea

Both caffeine and L-Theanine are generally recognized as safe by the FDA - caffeine intake up to 400mg daily,3 and L-Theanine up to 250mg as a functional food additive in several food categories.4

It's a well-known fact that caffeine improves cognitive performance. You can feel your energy levels rising after consuming a cup of coffee, for example. But did you know that L-Theanine interacts with caffeine?

This is why both L-Theanine and caffeine are common ingredients in energy drinks - they work together to create a steadier, smoother energy boost. We recently wrote an article explaining how they interact and the effects of this combination on your energy, alertness, focus, and creativity. Read Caffeine in Tea vs Coffee to learn more.


Sources of L-Theanine

Besides tea and supplements, there are very few sources of natural L-Theanine in the world. Bay bolete mushrooms, Xerocomus badius, is one. So, the best way to get a natural supply of L-Theanine is to join the tea drinkers in consuming green tea, black tea, or one of the other tea types produced by the Camellia sinensis plant.

Thankfully, L-Theanine is water soluble, so you can enjoy the beneficial properties that the studies below have found through oral administration just by brewing a cup of tea.

Keep in mind that many of these peer reviewed studies use small sample sizes and are just scraping the surface of what L-Theanine can do. More research is needed to provide concrete evidence!


Possible Health Benefits of Taking L-Theanine

matcha in a tea bowl

L-Theanine has shown promise that it could be used to treat certain conditions and diseases - maybe even prevent them in healthy people too. We've created summaries of the evidence from each placebo controlled clinical trial or systematic review below.


Attention Deficit Hyperactivity Disorder (ADHD)

Research suggests L-Theanine may improve attention span and reduce "mind wandering" when combined with caffeine, according to one study observing five boys (8-15 years) with ADHD.5

Furthermore, another study into the effects of L-Theanine on ADHD found that "400 mg daily of L-theanine is safe and effective in improving some aspects of sleep quality in boys diagnosed with ADHD." The researchers also note that long-term and larger studies to analyze the therapeutic role of L-Theanine should be prioritized next.6


Generalized Anxiety Disorder (GAD)

When looking at the impact of L-Theanine on anxiety, sleep quality, and cognition, researchers found that GAD-diagnosed participants treated with L-Theanine reported higher sleep satisfaction than those given a placebo. They go on to conclude that even though their small (46 participants) study didn't find a link between L-Theanine and treating GAD, further studies examining the link between L-Theanine and reduced sleep disruption are warranted.7

Another study involving healthy participants without psychiatric illness found that 200mg of L-Theanine a day could significantly reduce anxiety as a stress-related symptom.8


Schizophrenia and Schizoaffective Disorder

A study conducted with schizophrenia and schizoaffective disorder patients found that 400mg of L-Theanine a day (alongside any ongoing antipsychotic medication) reduced anxiety.

Interestingly, the study also notes that the 400mg daily dose - which is above the FDA recommendation of 250mg - did not cause side effects nor impact general functioning and quality of life. They conclude that L-Theanine could be a safe and well-tolerated medication that warrants further long-term studies.9


Sleep Quality

In the GAD study mentioned above, the results found that there was a subjective improvement in sleep quality - it was self-reported. However, there's also evidence of objective sleep quality improvement as well as duration.

A study involving L-Theanine and GABA found that administering 20mg of L-Theanine in mice increased sleep duration by 38.1% and decreased sleep latency (the time it takes to fall asleep) by 23.3%.

Furthermore, the study notes that the combination of L-Theanine and GABA (an inhibitory neurotransmitter that's also found in tea leaves in low amounts) improves sleep time and quality even more, compared to GABA or L-Theanine alone.10


Physical and Psychological Stresses

The studies above have shown that L-Theanine reduced stress levels and it's obvious that tea can reduce subjective stress too - take a sip of Zest Blue Lady and see for yourself.

There's also evidence that L-Theanine enhances recovery from physical stress. One study found that L-Theanine reduced the heart rate response to stress, as well as the psychological symptoms.11 And another hypothesized that L-Theanine could be used to improve functional recovery after traumatic spinal cord injury. The results indicated that the neuroprotective, anti-inflammatory, and antioxidant properties of L-Theanine show a great deal of promise.12


Mental Focus and Alertness

L-Theanine has a significant impact on brain function. Drinking tea not only increased subjective alertness but also sustained attention to demanding cognitive tasks in numerous studies.

One particular study examined the effects of L-Theanine when consumed at realistic dietary levels - 50mg - and found that:

"L-theanine, at realistic dietary levels, has a significant effect on the general state of mental alertness or arousal. Furthermore, alpha activity is known to play an important role in critical aspects of attention, and further research is therefore focussed on understanding the effect of L-theanine on attentional processes."13


Cognitive Performance

The study mentioned above discovered an increase in alpha waves in the brain after consumption of L-Theanine. This is important because alpha waves not only help you manage and reduce stress, but also boost your creative mental state.

An increase in alpha waves boosts your ability to produce innovative ideas.14


Neuroprotective Effects

L-Theanine is known to have anti-inflammatory and antioxidant effects, but it also plays a role in the immune system and with disease prevention.

Firstly, L-Theanine regulates glutamine metabolism. Glutamine is another amino acid, but one that we receive in abundance through our diet. It's a critical part of the immune system and is used to create proteins in the body.15

Secondly, research suggests that L-Theanine may enhance anti-inflammatory effects further by binding to cannabinoid receptors in the brain.16


The Best Tea for L-Theanine

two people drinking Zest Tea

At Zest, each of our teas provides up to 100mg of L-Theanine per serving, which is higher than standard tea yet still comfortably within the safe recommendation limit set by the FDA.

If you've ever tried a high L-Theanine tea before, you'll know that this particular amino acid gives tea that umami taste - rich and savory. Combined with our non-GMO flavor ingredients, our tea is both functional and delicious.

We don't need to conduct a double blind placebo controlled trial to tell you that!

Learn more about the L-Theanine tea flavors available at Zest.



Which tea has the highest L-theanine?

Zest Tea! We create plant-powered energy teas that utilize additional tea extract to naturally boost the levels of L-Theanine and caffeine in our blends. It's tea on tea. As a result, we know that there's approximately 100mg of L-Theanine per serving in our black and green tea.

This is high compared to standard tea, which initial research has found is between 24.2mg and 5.7mg in 200ml of black tea, and between 7.9mg and 3.8mg in green tea.17

How much L-theanine is in a cup of tea?

Unlike caffeine, most tea producers aren't overly concerned with measuring the amount of L-Theanine their tea drinkers are consuming. The general consensus is that green tea is high in L-Theanine, yet other research has found that black tea is an excellent source of it too.18 At Zest, we measure exactly how much L-Theanine makes it into our teas - there's 100mg in each ready-to-drink can.

What is L-theanine best for?

L-Theanine has numerous health benefits, including stress relief, improving cognitive function, and improving sleep quality. It can also promote relaxation and enhance alertness. There are several studies confirming these qualities - read our full list above.

Is drinking tea good for anxiety symptoms?

There are compounds in tea that can treat some anxiety symptoms - L-Theanine is a big one. However, caffeine itself may not be good for anxiety. Too much caffeine can cause a sudden and short spike in blood pressure, uncontrollable energy, and trouble focusing. So, if you are struggling with anxiety, we recommend a low-caffeine tea that's designed especially for anxiety, sleep, and relaxation. Discover Zest CBD Tea to learn more.

How much L-Theanine is in Zest green tea?

Each 12oz can of Zest Energy tea provides 100mg of L-Theanine and 120-150mg of caffeine, depending on the flavor you select. We use natural tea extract to boost our energy and L-Theanine levels above a standard cup of tea - it's totally plant powered.

What is an amino acid?

An amino acid is an organic compound that combines to create proteins. There are numerous kinds of amino acids - some are essential in our diet and some are even created by our own bodies. L-Theanine is not an essential amino acid nor is it created by the human body. The L-Theanine amino acid is only produced naturally in the Camellia sinensis tea plant.


HIGH CAFFEINE TEAS  We get it - you can't function before caffeine hits your bloodstream. Good thing Zest has more caffeine than coffee, plus your stomach won't hate you for drinking it.   ENERGY: 3X the amount of caffeine found in regular teas FOCUS: L-Theanine for all-day, steady alertness HEALTH: No surgar and made with completely natural ingredients  SEE PRODUCT PAGE

1 https://pubmed.ncbi.nlm.nih.gov/18296328/
2 https://en.wikipedia.org/wiki/Theanine#Effects
3 https://www.fda.gov/consumers/consumer-updates/spilling-beans-how-much-caffeine-too-much
4 https://www.cfsanappsexternal.fda.gov/scripts/fdcc/index.cfm?set=GRASNotices&id=209&sort=GRN_No&order=DESC&startrow=1&type=basic&search=l%2Dtheanine
5 https://pubmed.ncbi.nlm.nih.gov/32753637/
6 https://pubmed.ncbi.nlm.nih.gov/22214254/
7 https://pubmed.ncbi.nlm.nih.gov/30580081/
8 https://pubmed.ncbi.nlm.nih.gov/31623400/
9 https://pubmed.ncbi.nlm.nih.gov/21208586/
10 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6366437/
11 https://pubmed.ncbi.nlm.nih.gov/16930802/
12 https://pubmed.ncbi.nlm.nih.gov/31812333/
13 https://pubmed.ncbi.nlm.nih.gov/18296328/
14 https://www.sciencedirect.com/science/article/abs/pii/S0010945215001033?via%3Dihub
15 https://www.healthline.com/nutrition/glutamine#TOC_TITLE_HDR_2
16 https://pubmed.ncbi.nlm.nih.gov/34037653/
17 https://www.mendeley.com/catalogue/19936c44-b41a-352a-b8f7-c27ae3eb7aad/
18 https://www.mendeley.com/catalogue/19936c44-b41a-352a-b8f7-c27ae3eb7aad/