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. (1)
It’s been highly regarded in China for thousands of years for its ability to increase physical stamina, stimulate mental clarity, and promote longevity.
Over 1,300 chemical compounds have been identified in tea so far. (2)
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 Boletus badius.
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.
However, l-theanine is 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 which is considered the fifth taste sensed by humans.
Unlike many other molecules, l-theanine readily crosses the blood-brain barrier, making it an effective ingredient in brain health and performance supplements.
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.
By inhibiting the dopamine reward pathway, l-theanine has been shown to help smokers quit smoking. (9)
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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. (10)
2. L-Theanine Alleviates Stress and Anxiety
L-theanine diminishes the symptoms of anxiety by increasing GABA, a neurotransmitter that plays a crucial role in relaxation. (17)
When GABA is low, it becomes impossible to quiet your mind and you may often feel overwhelmed and overstimulated.
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L-theanine may 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. (18)
Additionally, when l-theanine is taken along with antipsychotic medication, it can reduce the anxiety symptoms of schizophrenia. (19)
3. L-Theanine Puts You in a Relaxed Brainwave State
One of the more intriguing ways l-theanine can bring about a state of calm is by altering your brain waves.
Your 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.
So you can experience benefits similar to meditation by taking a standard supplemental dose of l-theanine. (23)
You should notice its relaxing effects within 30 to 45 minutes.
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Besides l-theanine, tea also contains caffeine.
And fortunately for us, these compounds work synergistically when you drink tea. (24)
L-theanine and caffeine together can help you perform better on cognitively demanding tasks than caffeine alone, yet should not leave you feeling wired since l-theanine blunts the overstimulating effects of caffeine. (25, 26)
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.
L-theanine, especially when used with caffeine, can be a safe and effective way to maximize mental performance without resorting to brain-enhancing drugs. (29)
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5. L-Theanine Is Neuroprotective
L-theanine protects the brains of seniors and helps keeps them mentally sharp. (33)
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. (34)
It is neuroprotective against stroke and Alzheimer’s. (36)
L-theanine can help prevent the death of brain cells following a transient ischemic attack (TIA), a type of stroke. (37)
It can protect the brain from environmental neurotoxins thought to play a role in Parkinson’s disease. (38)
6. L-Theanine Enhances Sleep Quality
One last benefit of l-theanine is that it 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 your brain repairs itself, grows new brain cells, and consolidates the memories of the day.
One study found that 200 mg of l-theanine before bed improves sleep quality.
And unlike many other sleeping aids, it doesn’t leave you feeling tired the next day.
The Benefits of L-Theanine Supplements vs Tea
There are two main ways to get your 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 best way for now. (43)
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.
It’s a quandary!
Here are some other things to consider before you start taking supplements or drinking tea for its l-theanine content.
Supplemental l-theanine is quite popular for anxiety, high blood pressure, insomnia, and general stress relief.
L-theanine supplements are generally considered very safe. (44)
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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 generally recommended l-theanine dosage is 200-400 mg once or twice daily, with a maximum intake of 1,200 mg per day. (45)
The experts at Suntheanine report that some people experience noticeable benefits with as little as 50 mg and that nearly everyone will experience some degree of relaxation with a daily dose of 400 mg.
We suggest starting with a low dosage and note how you feel.
You can then gradually increase your dosage until you get the benefits you are looking for.
L-Theanine Side Effects, Warnings, and Interactions
Drugs.com gives l-theanine supplements the safety “thumbs up.”
There are no reported safety concerns despite widespread use, and no known drug interactions.
A few adverse reactions reported in studies using tea extracts include headache, dizziness, and digestive upset. (46)
Use l-theanine with caution if you take a high blood pressure medication since it can decrease your blood pressure. (47)
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 since its safety has not been determined for these groups. (48)
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 intake of tea is 5 cups per day. (49)
Drinking more is generally not advised due to the caffeine content. (50)
It doesn’t much matter the kind of tea you drink as a source of l-theanine since black, green, 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. (51)
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.
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 Green 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 3 weeks prior to harvest. (55)
This slows down growth, allowing the leaves to turn a deep shade of green and stimulates the production of l-theanine and chlorophyll. (56)
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, you 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 like to call matcha “green tea on steroids.”
It’s been reported that matcha contains up to 5 times more l-theanine than other teas. (57)
Matcha also contains more caffeine.
Here’s how the caffeine content of matcha and other teas compare (per 8 ounce serving): (58)
- Matcha tea — 70 mg
- Black tea — 42 mg
- White tea — 28 mg
- Oolong tea — 27 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. (59)
Too much tea can reduce the absorption of iron from food and can make anemia worse.
But adding lemon or milk eliminates this problem. (60)
If you are pregnant or breastfeeding, it’s advised to drink not more than 2 cups a day due to the caffeine content. (61)
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. (62)
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 list of interactions between tea and medications at RxList.com.
L-Theanine Benefits: The Bottom Line
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 make you feel calm and focused without drowsiness or stimulation.
It can improve your mood and your 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 your l-theanine from supplements or from drinking tea — black, white, oolong, and green tea all contain significant amounts.
But since both tea and supplements bring their own unique benefits to the table, and supplements contain no caffeine, there’s no reason you can’t drink tea and take a theanine supplement.