Last updated December 30, 2021.
Edited and medically reviewed by Patrick Alban, DC. Written by Deane Alban.
L-theanine, as a supplement or in tea, can reduce stress and anxiety, and boost mental health and performance, by inducing a state of calm attentiveness.
Tea is the most widely consumed beverage in the world and its health benefits are legendary.
It’s been highly regarded in China for thousands of years for its ability to increase physical stamina, stimulate mental clarity, and promote longevity.
So far, nearly 1,400 plant compounds have been identified in tea.
And, of all these compounds, l-theanine stands above the rest for its many benefits for mental and cognitive health.
What Is L-Theanine?
L-theanine (often referred to as theanine) is an amino acid that has a relaxing, but not sedating, effect.
It rarely occurs in nature and is found almost exclusively in true teas — white, green, oolong, and black teas — which come from the leaves of the same evergreen bush, Camilla sinensis.
L-theanine is also found in an edible mushroom called Xerocomus badius.
This is not a mushroom that you’ll find at your local supermarket, but it can be found growing wild in some forests of Europe and North America.
Many sources state that l-theanine is found only in green tea or that green tea is by far the best source of it, but this is not true.
Studies on the levels of theanine in various teas have generally concluded that it exists in similar amounts in black, green, white, and oolong teas.
One study, in fact, found black tea to have the most and green tea to have the least.
However, l-theanine continues to be most strongly associated with green tea because that’s where it was first discovered.
L-theanine is responsible for tea’s umami or savory taste, a flavor considered to be the fifth taste sensed by humans.
Unlike many other molecules, l-theanine readily enters the brain, making it an effective ingredient either on its own or when included in brain supplements.
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6 Mental Health Benefits of L-Theanine
While l-theanine offers many brain benefits, it’s most widely appreciated for its ability to bring about a state of focused relaxation and calm attentiveness.
Here’s a look at some of the specific benefits of l-theanine for stress, anxiety, insomnia, cognitive performance, and overall mental well-being.
1. L-Theanine Boosts Important Brain Chemicals
One of the main ways l-theanine impacts the brain is by boosting neurotransmitters, biochemicals that brain cells use to communicate with each other.
L-theanine increases the levels of some of the most important neurotransmitters, especially serotonin, dopamine, and GABA, thus improving recall, learning, and positive mood.
By acting on the dopamine reward pathway, l-theanine has been shown to help smokers quit smoking.
An interesting and unexpected benefit of l-theanine is that it acts as a neurotransmitter in the brain even though the body doesn’t naturally produce it.
L-theanine also increases two other important brain chemicals, brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF), that stimulate the growth of new brain cells and neurons, respectively.
2. L-Theanine Alleviates Stress and Anxiety
L-theanine can make you more mentally resilient by reducing both psychological and physiological stress responses.
It reduces the anxiety felt in social situations.
" L-theanine causes an increase in alpha activity, the brainwave state associated with relaxation and attention. This is the same brainwave state achieved during meditation.
It can lower your heart rate and help you maintain a healthy blood pressure when you’re under stress.
L-theanine diminishes the symptoms of anxiety by increasing the level of GABA, a neurotransmitter that plays a crucial role in relaxation.
When your GABA level is low, it becomes much harder to quiet your mind and you may often feel overwhelmed and overstimulated.
Research has found that l-theanine can work as well for anxiety as commonly prescribed anti-anxiety medications.
In one study, participants were given either l-theanine or Xanax and subjected to artificially induced stress.
Participants who received l-theanine had lower baseline anxiety than those who took Xanax.
Additionally, when l-theanine is taken along with antipsychotic medication, it can reduce the anxiety symptoms of schizophrenia.
3. L-Theanine Induces a Relaxed Brainwave State
One of the more intriguing ways l-theanine can bring about a state of calm is by altering brain waves.
Brain cells generate electricity to communicate with each other and this electrical activity forms patterns called brain waves.
There are five main brainwave patterns, each corresponding to a different state of awareness as shown in the chart below.
L-theanine causes an increase in alpha activity, the brainwave state associated with relaxation and attention.
This is the same brainwave state achieved during meditation.
So, you can experience benefits similar to meditation by taking a standard supplemental dose of l-theanine.
You should notice its relaxing effects within 30 to 40 minutes.
4. L-Theanine Synergistically Optimizes Mental Performance
Besides l-theanine, tea also contains caffeine and EGCG (epigallocatechin gallate).
And, fortunately for us, these three compounds work synergistically when you drink tea.
Caffeine and l-theanine together can help you perform better on cognitively demanding tasks than caffeine alone.
Unlike drinking caffeine alone, this combination should not leave you feeling wired since l-theanine mitigates the overstimulating effects of caffeine.
It’s this unique caffeine-enhancing property that makes l-theanine a popular supplement with those seeking optimal mental performance such as college students, workers in high-pressure occupations, and biohackers.
A mix of l-theanine and caffeine is a popular nootropic “stack” for boosting mood, focus, concentration, and alertness.
This duo can be a safe and effective way to maximize mental performance without resorting to brain-enhancing drugs.
If you want to make your own stack, typical ratios of l-theanine to caffeine range from 1:1 to 2:1 (e.g., 100 gm theanine for every 50 mg of caffeine).
The EGCG in tea normalizes the activity of GABA, a key relaxing brain chemical often referred to as “nature’s Valium.”
And, like l-theanine, EGCG alters your brainwave patterns, producing a relaxed, yet attentive, state.
5. L-Theanine Is Neuroprotective
L-theanine is neuroprotective — it protects the brain and nervous system from degradation and attack.
It protects the brains of seniors and helps keeps them mentally sharp.
Studies in traditional tea drinking countries like Japan and China found that seniors who regularly drank tea scored better on attention, memory, and information processing than those who did not.
Theanine has been shown to improve cognition and memory, even in people diagnosed with a type of cognitive decline known as mild cognitive impairment (MCI).
L-theanine protects against stroke and can help prevent the death of brain cells following a transient ischemic attack (TIA), a type of stroke.
It can protect the brain from environmental neurotoxins thought to play a role in Parkinson’s disease.
Another important way l-theanine protects the brain is by increasing blood flow.
6. L-Theanine Enhances Sleep Quality
L-theanine can help you sleep better.
This is important because getting high-quality sleep is one of the best things to do for your brain.
It’s during sleep that the brain repairs itself, grows new brain cells, and consolidates the memories of the day.
Unlike most natural sleep supplements which make you drowsy, l-theanine doesn’t put you to sleep, but it can help you sleep better.
One study found that 200 mg of l-theanine before bed improves sleep quality.
And unlike pharmaceutical sleeping aids, it won’t have you feeling drowsy the next day.
The Benefits of L-Theanine Supplements vs Tea
There are two main ways to get l-theanine — from tea and from supplements.
There are pros and cons to each.
Most experts agree that too few good studies have been conducted on the effects of theanine supplements on humans and that drinking tea is still the better option for now.
However, you will get only about 25 mg of l-theanine from a cup of tea, while most supplements contain 200 mg per serving.
Drinking that much tea, even decaffeinated, would require you to drink much more than the recommended amount of tea.
But keep in mind that there are many other healthful compounds in tea besides l-theanine.
“Tea vs l-theanine” does not have to be an “either/or” proposition.
There’s no reason you can’t take drink tea and take an l-theanine supplement.
Suntheanine — a Patented Theanine Supplement
When looking for l-theanine supplements, you may come across Suntheanine®.
This brand of l-theanine supplement holds over 40 US and international patents.
Suntheanine is not extracted from tea, but is produced via a fermentation process much like the natural process that occurs when tea leaves ferment to make green tea.
Suntheanine is often used in research studies when a standardized formulation is required.
L-Theanine Supplement Dosages
L-theanine is not an essential nutrient, so there is no recommended dietary allowance (RDA).
But the usual recommended l-theanine dosage is 200-400 mg once or twice daily.
Results of Suntheanine’s clinical research found dosages in the range of 50 to 200 mg per day to be effective.
We suggest starting with a low dosage, then note how you feel.
You can then gradually increase the dosage until you get the benefits you are looking for.
L-Theanine Supplement Side Effects, Warnings, and Interactions
L-theanine supplements are generally considered very safe.
There are no reported safety concerns despite widespread use, and few drug interactions.
A few adverse reactions reported in studies using tea extracts include headache and drowsiness.
However, you should use l-theanine with caution if you have high blood pressure.
It can lower your blood pressure and thus change your need for medication.
Talk to your doctor about taking l-theanine if you are undergoing chemotherapy or taking cholesterol-lowering medicines or sedatives since l-theanine can alter the effects of these drugs.
Lastly, l-theanine supplements are not advised for pregnant or breastfeeding women because its safety has not been determined for these groups.
However, drinking 2 cups of tea per day has been deemed safe during pregnancy.
How to Get the Most L-Theanine From Tea
If you choose to get your l-theanine from tea, how much should you drink?
The recommended maximum tea intake is 5 cups per day.
Drinking more is generally not advised due to the caffeine content.
It doesn’t much matter the kind of tea you drink as a source of l-theanine since black, white, oolong, and green teas all contain similar amounts.
But you can affect how much l-theanine is in your tea by how you brew it and drink it.
Brewing time is the biggest determinant of how much l-theanine a cup of tea will contain.
So, if you want to get the most l-theanine from your tea, always brew the full steep time per this chart below.
Note that only the top five teas on this chart are true teas, i.e., from the Camilla sinensis plant.
If you decide to drink green tea, note that the general consensus among experts is that you need to drink 3 cups per day to experience any real health benefits.
And while pu-erh is a very expensive true tea enjoyed by tea connoisseurs, be aware that it does not contain l-theanine.
And finally, there’s evidence that milk binds to l-theanine, making it unusable.
While it seems that a little milk is not a problem, a generous splash of milk significantly reduces the amount of l-theanine detected in tea.
Matcha Tea: The Top Source of L-Theanine
Matcha is a type of green tea considered the “champagne of teas.”
Matcha tea leaves are of the highest quality.
The tea plants are shaded to protect them from direct sunlight for three weeks prior to harvest.
This slows down growth, allowing the leaves to turn a deep shade of green, and stimulates the production of l-theanine and chlorophyll.
When the young leaves are ready, they are hand-picked and air-dried.
Stems and veins are sorted out and what is left is stone-ground to become a bright green, finely milled powder.
To prepare a cup of matcha tea, dissolve this powder in water.
Since matcha contains whole dried tea leaves, you get 100% of available nutrients.
It is so rich in nutrients, I call matcha “green tea on steroids.”
While the amount of l-theanine in matcha varies widely from product to product, it can contain much more l-theanine than other teas.
Matcha also contains more caffeine.
Here’s how the caffeine content of matcha and other teas compare (per 8 ounce serving):
- Matcha tea — 70 mg
- Black tea — 42 mg
- Oolong tea — 37 mg
- White tea — 28 mg
- Green tea — 25 mg
Potential Side Effects of Tea
If you decide to get your l-theanine from tea, there are a handful of side effects you should be aware of.
Tea is generally considered safe with almost no known side effects unless you consume too much caffeine.
Side effects of too much caffeine include anxiety, insomnia, headache, irregular heartbeat, restlessness, tinnitus, and nausea.
Too much tea can reduce the absorption of iron from food and can make anemia worse.
If you are pregnant or breastfeeding, it’s advised to drink not more than 2 cups a day due to the caffeine content.
According to Drugs.com, green tea should not be taken with the anticoagulants warfarin, dicumarol, and anisindione.
The small amount of vitamin K in green tea can interfere with the effectiveness of these drugs.
Some medications should not be mixed with tea because of the overstimulating effects of caffeine.
Others exhibit a decrease in activity when combined with tea.
You’ll find a comprehensive list of interactions between tea and medications at RxList.com.
L-Theanine Benefits: Take the Next Step
Tea is unarguably one of the healthiest drinks around and l-theanine is responsible for many of tea’s benefits.
L-theanine is highly regarded for its unique ability to increase calm and focus, but without drowsiness or stimulation.
It can improve your mood and ability to concentrate.
Theanine can boost brain health and function now, and help prevent mental decline in the future.
It can help you get the restorative sleep your brain needs to function its best.
You can get l-theanine from supplements or from drinking tea — black, white, oolong, and green tea all contain significant amounts.
Or you can take l-theanine as a supplement, either on its own or as part of a proprietary formula.
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