L-Theanine: Benefits, Side Effects, Best Time to Take It & More

L-Theanine

(Theanine)

Evidence: High
Possible Benefits: Very High
Safety: Very High

What is L-theanine?

L-theanine is a non-essential amino acid that naturally comes from tea. As a supplement, most people use it for reducing stress and anxiety and improving sleep quality. Theanine works best when paired with caffeine as it can significantly reduce some of the unpleasant effects of caffeine. This article is about the main benefits of L-theanine, its potential side effects, the best time to take it, and more.

What does L-theanine do for the body?

L-theanine can easily cross the blood-brain barrier. In the brain, this amino acid promotes alpha waves, which are associated with calmness and relaxation.

Possible benefits

The benefits mentioned below are dose-dependent. Generally, the higher the dose, the more pronounced the effects are. However, they do reach a plateau at a certain point. We will discuss the best dosing protocol later in this article.

Major benefits

Relaxation – Theanine notably increases relaxation 30-60 minutes after it is ingested. This usually doesn’t lead to sedation.
Reduced stress and anxiety – The supplement can reduce most types of anxiety, some of which to a remarkable degree. Anticipatory anxiety seems to be unaffected.
Improved sleep – L-theanine can improve sleep in people with stress, anxiety, ADHD, or those who drink caffeine before bed.
Cognitive enhancement – Cognitive benefits (such as an improvement in memory and problem-solving abilities) are most notable when you combine theanine with caffeine.

Minor benefits

Improved attention – A significant improvement usually occurs in stressed people or people with high anxiety. Those with little to no stress and anxiety are unlikely to see any improvement in concentration and attention span.
Reduced blood pressure – This benefit only seems to apply when you combine L-theanine with caffeine or when you take it in a high-stress situation.
Reduced symptoms of schizophrenia – High doses (400 mg) of theanine can reduce anxiety and psychotic episodes related to schizophrenia.

Possible side effects

These side effects are dose-dependent. The risk for them increases (often linearly but sometimes exponentially) as you increase the dose. Some of the side effects only apply to very high doses.

Nausea
Diarrhea
Headaches
Toxicity – L-theanine is one of the safest supplements and should not do any harm even at very high doses. With that said, taking multiple grams a day for a prolonged period could cause some harm in the long term, although even these doses appear very safe. For most of us, there is no reason to take more than 200 mg of theanine at once.
Contamination – Contaminated supplements are uncommon in the USA and other well-regulated countries. However, if you wish to buy products from China, India, or other countries without strict regulations, beware that the supplements may be contaminated. Either way, you need to choose the brand you order from wisely. It is highly recommended to check the certificates or read through some reviews for the specific product before you buy it. The FDA (Food and Drug Administration) has the power to regulate dietary supplements but can only do so after they have been on the market for a while. That’s because supplement companies are not obligated to announce to the FDA when releasing a new product on the market. The FDA has to discover the product and test it for potential impurities, which can take a lot of time. During that time, the supplement can be sold on the market even if it’s impure. Also, supplement companies can change their manufacturers without announcing it to the FDA.

Who should not take L-theanine?

You should probably avoid taking the supplement if you:

experience a severe adverse reaction after taking the amino acid

Who will benefit the most?

You should consider taking the supplement if you:

take caffeine supplements or drink lots of coffee
prioritize cognitive health
experience a lot of stress and anxiety
have ADHD
suffer from schizophrenia
wish to improve sleep quality
have a high budget for supplements (theanine is one of the safest supplements on the market and will almost certainly do more harm than good)

How much L-theanine should you take?

If you plan to take L-theanine as a supplement, 100-200 mg appears to be the best dose for most people to take at once. This amount should provide most of the benefits without any side effects.

The half-life of theanine in the body is relatively short (54-78 minutes). Since the absorption of theanine becomes significantly worse when you go over 200 mg at once, you will get the best results when you take 100-200 mg multiple times a day, as opposed to taking a higher dose at once.

Some people may benefit from doses higher than 200 mg at once. For example, schizophrenics who experience states of high anxiety and psychosis seem to benefit more from 400 mg taken multiple times a day.

Since theanine acts synergistically with caffeine in many ways, it is best to consume them together. The optimal ratio seems to be about 2 mg of theanine for every 1 mg of caffeine.

If you consume more than 100 mg of caffeine at once, taking over 200 mg of L-theanine is unnecessary at that time as most of the theanine beyond 200 mg wouldn’t get utilized. In this case, it is best to take 200 mg and then another 100-200 mg 3-4 hours later.

L-theanine is one of the safest supplements and should not do any harm even at very high doses.

Taking multiple grams a day for a prolonged period would be unnecessary and could cause some harm in the long term, although even these doses appear very safe. For most of us, there is no reason to take more than 200 mg of theanine at once.

Best time to take L-theanine

To maximize the benefits, take L-theanine when you consume caffeine.

The optimal ratio of L-theanine to caffeine is about 2:1. If you consume more than 100 mg of caffeine at once, just take 200 mg of L-theanine with it and then another 100-200 mg 3-4 hours later.

If you drank coffee or took caffeine in the afternoon or later, take theanine before going to bed to reduce the negative impact of caffeine on sleep quality. Theanine can also improve sleep quality if you don’t drink any caffeine close to bedtime.

L-theanine is water-soluble, so you don’t have to take it with food to absorb it well. To maximize absorption, take the supplement at least an hour before or after a meal so it doesn’t compete for absorption with other amino acids.

Unless it feels too impractical, spread the daily dose into 2+ smaller doses throughout the day.

The half-life of theanine in the body is relatively short (54-78 minutes). Since the absorption of theanine becomes significantly worse when you go over 200 mg at once, you will get the best results when you take 100-200 mg multiple times a day, as opposed to taking a higher dose at once.

Sources of L-theanine

Tea is by far the most abundant source. A cup of green or black tea contains on average 25 mg of theanine.

Matcha contains about 20 mg per cup. White tea and yellow tea contain anywhere from 2-14 mg. Oolong tea is low in theanine with only 4 mg per cup.

Pu-erh tea has hardly any l-theanine. That is the main difference between Pu-erh and black tea as far as how it impacts the body.

Coffee, yerba maté, and most other non-tea caffeine sources don’t have any L-theanine in them.

Sources of caffeine

Caffeine supplements – Even though many of the benefits above also apply to caffeine supplements, it is not the preferred way to take the compound because you would miss out on all of the other benefits of guarana, tea, coffee, or other sources. Caffeine supplements are rarely worth it unless you are a serious athlete or hate the taste of caffeinated beverages. Even in those cases, guarana supplements or tea and coffee extracts would be much better.
Guarana – Guarana (Paullinia cupana) is a plant traditionally used in and around the Amazon rainforest. The seeds of Paullinia contain more caffeine than coffee or any other plant in the world (3.6-5.8% of their dry weight is caffeine).
Coffee – The caffeine content of coffee varies greatly from cup to cup. Generally, a regular cup of coffee contains between 40 and 180 mg, with the average being around 135 mg. So if you drink coffee that is not too intense, you can probably count one cup as 135 mg. Decaffeinated coffee only contains about 2 mg per cup.
Green tea – An average cup contains around 20 mg of caffeine and 50-100 mg of EGCG.
Decaf green tea – Decaffeinated green tea contains on average 1-2 mg of caffeine and 60 mg of EGCG per cup.
Matcha green tea – Matcha is significantly higher in both caffeine and catechins than other forms of green tea. Or, more precisely, you get to consume more of these since you swallow the powder.
Pu-Erh – Pu-Erh is comparable to black tea as far as its caffeine and catechin content.
Black tea – Black tea contains about 2 times as much caffeine as green tea, so on average 40 mg. Unfortunately, it is not very high in catechins and only contains around 10 mg of EGCG per cup.
Oolong tea – Oolong tea’s caffeine and catechin content are somewhere between green and black tea. An average cup contains 30 mg of caffeine and 40 mg of EGCG.
White tea – White tea has around the same level of catechins as green tea and contains an average of only 10 mg of caffeine per cup. This is a very good thing because it allows you to drink a lot of white tea and reap more benefits connected to EGCG and other catechins in it.
Yellow tea – This type is extremely similar to white tea.
Cacao – Cocoa powder has around 0.21% caffeine by weight. Therefore, one gram contains an average of 2.1 mg.
Yerba maté – Yerba maté has a much higher caffeine content than regular tea. Typically, an average cup of yerba maté contains about 80 mg of caffeine.
Soda and energy drinks – This is undoubtedly the worst way to consume caffeine, mainly because of the sugar and/or artificial sweetener content in these drinks. There are brands on the market that sell relatively harmless energy drinks sweetened with stevia, xylitol, or erythritol. While these are definitely a better choice than regular energy drinks, they are still not better than coffee, tea, or other natural sources. As for caffeine content, energy drinks almost always contain around 30 mg per 100 ml and coke contains around 10 mg per 100 ml.

Food/beverage	Amount of caffeine
Green tea	20 mg/cup
Black tea	40 mg/cup
White tea	10 mg/cup
Yerba maté	80 mg/cup
Coffee	135 mg/cup
Oolong tea	30 mg/cup
Decaf tea	1 mg/cup
Decaf coffee	2 mg/cup
Coke	10 mg/100 ml
Energy drinks	30 mg/100 ml
Cacao	2.1 mg/gram

What type of tea is the healthiest?

To determine what the healthiest type of tea is, we need to consider 2 things:
1) The benefits per cup
2) The caffeine content

For example, people often compare green and black tea together. Their polyphenol content is roughly equal (green tea is much higher in catechins but black tea contains more theaflavins). Because of that, the long-term benefits per cup are similar. However, green tea has on average 2 times less caffeine in it, making it 2 times more beneficial per mg of caffeine.

Caffeine itself is not necessarily a harmful compound and it is responsible for many of the benefits of tea. However, it limits the amount of tea you can safely drink per day (especially when it comes to the high-caffeine types, such as black tea and Pu-Erh).

So which tea type is the best depends on whether you are looking for the most benefits per cup or benefits per amount of caffeine.

If you are looking for the most benefits per cup, matcha gyokuro appears to be the best choice. Gyokuro is a type of green tea that appears to be the highest in EGCG and other catechins. Whichever type of green tea you are consuming, choosing a powdered form (matcha) will allow you to get the most catechins out of it.

If you are looking for the most benefits per 1 mg of caffeine, matcha gyokuro is still one of the best types but it does not deserve the #1 spot. The winner in this category would probably be some form of yellow or white tea since these are almost just as high in beneficial compounds as green tea but much lower in caffeine (typically around 10 mg per cup). This allows you to safely drink almost as much white/yellow tea as you wish and thus reap a lot more benefits.

Oolong tea is somewhere between green tea and black tea as far as the caffeine content and health benefits go.

As for Pu-erh tea, it is almost identical to black tea as far as its composition and health effects. The main difference between the two is their l-theanine content. Black tea contains around 25 mg of l-theanine per cup, while Pu-erh contains little to no l-theanine.

So to summarize, matcha green tea, white tea, and yellow tea can all be considered the healthiest types, depending on your definition of healthiest. However, that doesn’t take away from other types of tea, as they can be more useful for specific purposes.

We did not take into consideration herbal teas as that is a completely different category with vastly different effects.

Interactions

Caffeine
L-theanine is able to reduce most of the negative effects of caffeine, such as anxiety, jitteriness, and even the negative impact on sleep quality. If you consume a lot of caffeine, it is highly recommended to combine it with 100-200 mg of l-theanine. Besides theanine’s ability to lower the side effects of caffeine, the combination is also very effective at improving focus and attention. It has also been shown to protect people from cognitive decline to some extent.
EGCG
EGCG and green tea catechins in general can act synergistically with theanine for supporting cognitive health. This combination may protect you from cognitive decline to some extent.
Sedatives
L-theanine is not a sedative and does not cause drowsiness. However, it may increase the sedative effects of other substances by calming you down even further. This can be viewed as a good thing if you are willing to take a lower dose of a certain sedative when you combine it with L-theanine.

Where to buy L-theanine

Amazon is the best option for ordering L-theanine supplements in most countries. They offer some very affordable products backed by many positive reviews. Also, you can choose from a wide range of brands without having to search through other markets on the internet.

Beware some brands display the dosage per serving instead of per pill or capsule. Therefore, you may accidentally buy something less potent than you intended. Do not fall for this marketing trick.

FAQ

Like most other supplements, it is best to cycle L-theanine and take a break from it for about two days per week to reset your tolerance back to baseline. That will keep your body sensitive to the supplement and allow you to keep getting the benefits in the long term. If you’ve been taking theanine daily for a long time, it may take up to 10 days to reset your tolerance back to baseline.

Unfortunately, coffee doesn’t contain any theanine.

One cup contains on average 25 mg of L-theanine.

Just like green tea, black tea has about 25 mg of theanine per cup.

All of these options are fine. The two most important things to consider are the price and dosing. Powders are almost always the cheapest form. However, you may need a highly accurate scale to dose them correctly (preferably 0.001g). You can get one for as little as $20 from Amazon. Dosing the powders also takes some time that can add up over months or years. The disadvantage of capsules is that they often contain bovine gelatin, which rarely comes from an ethical source.

Yes. L-theanine can improve sleep quality when you take it before bed, especially if you are stressed or if you drank caffeine in the afternoon or later.

This amino acid should not become harmful once it exceeds the expiration date but can lose potency over time.

Keep the supplement in a cold, dark, and dry place, and it should remain just as potent for many months or even years.

L-theanine is one of the safest supplements and should not do any harm even at very high doses. With that said, taking multiple grams a day for a prolonged period could cause some harm in the long term, although even these doses appear very safe. For most of us, there is no reason to take more than 200 mg of theanine at once.

You may need more of this amino acid if you:
– eat very little protein (less than 0.3 grams/pound of body weight)
– take caffeine supplements or drink lots of coffee
– prioritize cognitive health
– have ADHD
– experience a lot of stress and anxiety
– suffer from schizophrenia
– wish to improve sleep quality

The half-life of L-theanine in the body is 54-78 minutes. This amino acid should get processed in your body within a few hours after you consume it.

The half-life of caffeine can be anywhere from 1.5 hours to 9.5 hours, depending mainly on your genes. The average half-life is 5-6 hours. Therefore, it takes a few days for the compound to fully leave your system but the effects will be less and less potent.

You should notice the effects almost immediately after taking the supplement.

Most pills and powders with L-theanine are vegan-friendly but always check the label to be sure. If you buy the amino acid in a capsulated form, beware that the capsules often contain animal-based gelatin. Instead, find a brand that puts its products into cellulose capsules.

Like most other amino acids, L-theanine is water-soluble, so you don’t have to take it with food to absorb it well.

L-theanine should not break a fast unless you take a very high dose at once. If you practice time-restricted eating, take this amino acid during your eating window so it doesn’t break your fast.

References

Most of the information provided in this guide is supported by scientific research that can be found and verified in the PubMed medical library. We highly encourage you to use the library to verify anything said in this article. We excluded from consideration studies that are either confounded or have a high conflict of interest.

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