L-Theanine Review: Benefits, Dosage, Side Effects & A Surprise [2019] 4.67/5 (3)

L-theanine is an amino acid found in tea leaves. It’s one of the most popular nootropics because it provides a whole range of mind-blowing benefits. But should you supplement it? 

Promotes relaxation without drowsiness

Helps with fat loss

Works well with caffeine

May cause upset stomach or nausea


1. L-Theanine Review

L-Theanine is a naturally occurring substance that can be found in the Camellia sinensis leaves (commonly known as tea leaves) and in a rare species of mushrooms.



It is a non-dietary amino-acid, which means it’s not urgent for us to take it on a regular basis, but in some cases, it definitely helps. It has been highly touted in recent years for its high antioxidant content, numerous health benefits and helping with fat loss.

Theanine promotes relaxation without drowsiness. So after a long day’s work, theanine will help you unwind and relax, but will not knock you out to sleep (though it might help you nevertheless).

It’s this relaxing and attention-boosting characteristic of theanine that often makes it a popular addition to a nootropic stack.

Theanine works very well with stimulants like caffeine, because it promotes attention and focus, but lessens the anxiety you may experience when taking stimulants by themselves.

2. L-Theanine: How Does It Work?

Theanine takes three different routes to improve our cognitive performance:

1. It supports GABA levels and produces a calming effect. [1] Gamma-Aminobutyric Acid, or GABA, is a neurotransmitter, which blocks impulses in the brain. By inhibiting particular nerve impulses, GABA promotes a state of calmness and relaxation, while low levels of GABA may lead to anxiety and a bad mood.

2. It increases alpha brain waves, which are associated with the state of relaxation, alertness and focus. [2] This is what makes theanine stand out in the crowd – it gives us a focus boost without the jittery feeling you might get when ingesting caffeine.

3. Affects glycine levels which are involved in dopamine and serotonin secretion. [3] Even though theanine only slightly raises glycine, dopamine and serotonin, it still has a calming effect on the mind while also promoting the feeling of happiness.

L-Theanine is a mild cognitive booster that relaxes our mind without making us sleepy, helps drown out distractions, and gives us a clear and stable focus on the task at hand.

But does it provide any other benefits?

3. L-Theanine Benefits

Let’s check out the main benefits of supplementing L-Theanine.

1. L-Theanine Improves Focus

L-Theanine is often supplemented due to its focus-boosting benefits.

If you combine it with caffeine (100 mg of caffeine with 200 mg of L-Theanine), your focus should improve even more. [6]

Actually, another similar study found that this powerful nootropic combo can provide benefits in just 30 minutes after you take it. [7]

Because of those reasons, L-Theanine has become one of the most popular nootropics on the market.

L-Theanine Benefits

L-Theanine Benefits

2. L-Theanine Helps With Stress

Another reason for supplementing L-Theanine is its power to help us deal with stress and anxiety.

There are several studies that prove the anti-stress properties of this amino acid.

Actually, one study found that supplementing L-Theanine increases relaxation without causing any drowsiness, which makes it an (almost) perfect supplement. [8]

I also found 5 controlled trials (104 participants) which found that L-Theanine proved very effective for people in stressful situations. [9]

But that’s not all.

3. L-Theanine Control Blood Pressure

Supplementing L-Theanine can be beneficial for people who have increased blood pressure.

I found a study which focused on observing healthy people that experienced high blood pressure during challenging tasks. [10]

What did the study find?

Well, L-theanine proved helpful once more.

Actually, it effectively controlled the blood pressure increase in the participants.

4. L-Theanine Might Improve Sleep

I’m sure you wonder how can a compound increase our focus and improve our sleep at the same time?

Well, let me explain.

A study found that people who were given L-Theanine supplement for 6 weeks reported improved and more restful sleep.

Another study showed that supplementing 250-400 mg of L-Theanine improves the quality of our sleep. [8]

While I wouldn’t recommend using L-Theanine as the only ingredient for improving sleep, it helps out to supplement it during the day or drinking a cup of green tea in the evening.

L-Theanine Sleep

L-Theanine Sleep

4. L-Theanine Dosage

The easiest way of ingesting theanine is by drinking tea. You could substitute some of your daily cups of coffee with green tea.

Once you get used how to properly prepare a cup of tea, it’s quite easy to get your theanine “the natural way”.

L-Theanine dosage

L-Theanine dosage

While there’s nothing wrong with drinking tea to ingest theanine, it is easier to take it in powder form or in capsules.

With the recommended dosage, which is between 100 mg and 200 mg, a 200 ml cup of green or black tea yields anywhere between 10-60 mg of theanine (the numbers vary based on the type of tea and its steeping time), so you’re looking at a lot of tea you’d have to drink to get a considerable effect from the ingested theanine.

Use 100 mg – 200 mg of L-Theanine per day to unwind and get a clear-cut focus for your cognitive endeavors.

5. L-Theanine Side Effects 

L-Theanine by itself is a very mild nootropic, and the side effects should be minimal, should they occur at all. As with any other thing in life, practice moderation and you’ll be fine. Drink too much tea or take too much theanine and you may get the same results as with drinking large amounts of coffee.

The side effects include:

  • Upset stomach,
  • Nausea
  • Irritability

One side-note: despite some research showing theanine also possesses anti-tumor properties, drinking green tea and supplementing with L-Theanine is not recommended for people currently undergoing chemotherapy.

Compounds, known as polyphenols, found in green tea can actually reduce the efficacy of some chemotherapy drugs, so it is very important for people taking them to consult their physicians before drinking large amounts of green tea during their treatment. [4]

L-Theanine Review

L-Theanine Review

6. L-Theanine And Caffeine

Stacking theanine is very easy, and there is only one compound that truly works in synergy with L-theanine.

If caffeine is Batman, think of theanine as his trusty sidekick Robin.

Adding 50 mg of caffeine to 100 mg L-Theanine has been proven to significantly improve the accuracy and attention during cognitive testing of healthy adult individuals. [5]

The use of caffeine in isolation ranges around 150 mg that improves perceptions of fatigue and rapid visual information processing.

When adding 250 mg of L-Theanine, subjects experienced improved reaction time and the prolongation of the mentioned effects, making this combination of caffeine and theanine also a very good “pre-workout” stack.

7. L-Theanine Reviews

Reviews of both tea and theanine supplementation are quite favorable. Users report the compound has a calming effect albeit a very mild one:

“I am an adult male with generalized anxiety disorder, I have taken benzos and antidepressants but the side effects were not worth it. L-Theanine, while mild, is effective in reducing my anxiety and stress enough for me to not feel miserable every day and it also helps me sleep. I have never experienced a negative side effect from it and I have been taking it almost daily for several months.”

“My holistic friend recommended this supplement to me after the passing of my Mom. I could not rest, & my emotions where off the charts! But after using this for couple of days along with 5 HTP I have been calmer and more in control of my emotions, without feeling all drugged up or walking around in a daze.”

“I have been taking L-theanine for over a year for stress, anxiety and menopausal support. I wasn’t sure it was working until I was out of the product for over a week and all my stress, anxiety has returned. I will never be without my L-theanine again.”

“I had great results. It enhanced my cognitive thinking and less3ned my memory loss. The only problem was it gave me an unbelievable body odor. I could smell it but not sure if anyone else could. No one mentioned me smelling bad.”

“I have trouble turning off my brain as soon as the lights go off at bed time. I some times get only 4 hours of sleep. This melatonin plus 200gm L-theanine is helping me go to sleep and stay asleep. I am type 2 Diebetic and I have also noticed my blood sugar levels are much better.”

8. Where to Buy L-Theanine?

We see that L-Theanine is a great cognitive booster for people who are looking for a calm and collected approach to their mental work. It is easily available in the form of green and black tea, both of which can be found in almost any grocery store near you. Here you buy a great variety of green teas.

Another option is buying L-Theanine in capsules – my favorite product is Smart Caffeine, which is a mix of caffeine and L-theanine.

You can read more about it here >>

However, my ultimate recommendation is going for a more advanced nootropic stack that includes caffeine + L-theanine, but also a huge range of other nootropics.

My favorite one is Qualia Mind, which is also one of the most advanced nootropic stacks on the market.

I suggest checking it out here >>

Qualia Mind

Qualia Mind

9. My Recommendation

L-Theanine has been part of my daily nootropic regime for longer than I knew what nootropics are.

I’ve always loved drinking green tea without really knowing why does it have such a calming effect on me.

Honestly, I do prefer drinking green tea compared to taking supplements, but now and then supplements are the only available option.

I don’t take L-theanine on a daily basis, but it’s definitely on my table 3-5 times/week.

I love its smooth effect of relaxation and it works extremely well with caffeine.

So, definitely try it out and I’m sure most of you will love it.

10. FAQ

  • What does L-theanine do?

Theanine is a great relaxing agent, meaning it will calm you down, but it won’t make you sleepy. Theanine also slightly stimulates the brain and may improve your attention, but to really get an intense focus, combine theanine with caffeine.

  • What are the side effects of taking L-Theanine?

You shouldn’t feel any negative side effects when ingesting theanine. Some people have reported having an upset stomach after drinking too much green tea, but that is probably more because of the bitter taste profile of the beverage, rather than the contents themselves.

  • Should I drink green or black tea?

If you decide to drink tea for its nootropic features and not for its taste, then you’re looking at a question that has two answers. While the effects of drinking tea will not be as intense as taking theanine in powder form, I’d recommend going with green over black tea, as it contains slightly more theanine. If you’re looking for a bit more caffeine, however, choose black tea instead.

  • Why should I choose pure theanine and caffeine over tea?

Most studies have shown discrepancies in the L-Theanine to caffeine ratios in green and black teas, so you can never really know for certain how much of either compound you’re getting with a cup of tea. Measuring out powder takes the guesswork out of the equation, and you’ll end with similar results every time you decide to use the two substances together.

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By |2019-06-07T15:28:04+00:00October 17th, 2018|Categories: Nootropics|Tags: |0 Comments

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Thanks !

Thanks for sharing this, you are awesome !