L-Theanine is a Useless Nootropic, Except in this One Instance!

Casey ThomasUncategorizedLeave a Comment

But before we can talk about L-theanine, we need to first define ‘nootropic’.

Nootropics are drugs, supplements, or other nutritional substances that are claimed to improve cognitive function in otherwise healthy individuals. 

Note: The operative word is ‘healthy’. 

We’re not talking about people with cognitive decline, dementia, Alzheimer’s disease etc. We’re not even talking about healthy elderly. We’re talking about compounds that take a normal, healthy person and make their brain performance even better.

Sounds awesome, right? I know you’ve seen Limitless.

Unfortunately, if a Limitless drug did exist, you would know about it. More often than not, nootropics fall flat. They tend to only actually work if you are in a clinically deficient state, and are just correcting for that deficiency, or are someone with cognitive decline, dementia, Alzheimer’s disease, etc.

It is very rare to find a compound that truly takes a normal, healthy brain from 100 to 110%.

So what about L-theanine?

L-theanine has received a lot of attention recently in the nootropic world. There are many people who believe it does help with brain performance in healthy individuals. My goal with this article is to review the literature for you so we can see if that’s true.


Tea is a beverage that has been consumed across the world for centuries. There are loads of claims about tea. It’s been said to relax and improve energy, focus, and mood. We know that L-theanine is a component of tea.

Changing topics slightly – the brain has a giant filter around it, called the blood brain barrier (BBB). There are all sorts of filters in the body, but the one around the brain is the most selective (which makes sense because your brain needs the most protection). A compound would need to be able to cross the BBB to be able to enhance brain performance. 

Interestingly, L-theanine (and caffeine) both readily cross the BBB. Early scientists connected the dots and speculated that these compounds were likely responsible for the effects of tea drinking on brain performance because they were the only ones actually making it to the brain.

The next step was to test that hypothesis. They isolated out L-theanine, gave it directly to people, and watched what happened.

What Happened?

Studies using doses from 50-250 mg L-theanine have consistently shown a relaxing effect. For reference, one cup of green tea has approximately 20-40 mg of L-theanine depending on the type, brew, size, etc.

From these studies, scientists were able to conclude that L-theanine is likely responsible for the relaxing effects observed when drinking tea.

More research was done to tease out the details. Some highlights:

  • Blood levels of L-theanine peak at about 60 minutes after ingestion 
  • Effects of L-theanine last about 8-10 hours 
  • Mechanism appears to be related to an increase in dopamine and decrease in serotonin

What About Performance Metrics?

Haskell (2008) wanted to test the acute cognitive and mood effects of 250 mg L-theanine, 150 mg caffeine, or their combination (1). They found that L-theanine alone marginally improved one metric (choice reaction time), but significantly slowed down several metrics of cognitive processing. Specifically, L-theanine alone worsened numeric working memory, word recall, and ability to complete the serial 7 subtraction task (measures concentration and memory). 

The caffeine group saw many performance improvements, which is consistent with previous literature. Interestingly though, the group consuming L-theanine plus caffeine had even greater effects than caffeine alone: 

  • Improved simple reaction time
  • Improved word recognition reaction time
  • Improved speed and accuracy of rapid information processing
  • Greater reduction in mental fatigue and tiredness
  • Improved alertness 
  • Improved sentence verification 

Other studies with smaller doses confirm this relationship. Doses as small as 100 mg L-theanine with 50 mg caffeine show that the two interact to produce better attention, speed, and accuracy than caffeine alone. 

The punchline?

L-theanine alone, at best, does nothing for the brain. And we have data showing it frequently decreases performance. Not what we want!

L-theanine with caffeine is something magical. We see a 1 + 1 = 3 situation, where the whole is greater than the sum of its parts (check out my Not-So-Secret Stack)

But can L-theanine ALONE be useful?

I did promise in the title that L-theanine alone can be beneficial. Let’s talk about how.

We know L-theanine helps relieve anxiety and stress. As a high performing individual in the modern world, I’m sure you’re stressed out. You might hide it well, but I know you have lots of pressures on you and stressors in your life. 

Life isn’t easy. I get it.

Stress and anxiety degrade our ability to concentrate, process, and execute at a high level.

There was a study by Higashiyama (2011) that examined the effects of 200 mg L-theanine on attention and reaction time in healthy individuals (2). The interesting spin they did was stratify the participants into a ‘high propensity for stress’ group or ‘low propensity for stress’ group.

Participants ingested their treatment (L-theanine or placebo) and then completed the following cognitive tasks at 0, 15, 30, 45, 60 minutes post-ingestion:

Task 1: A random number from 1-9 was displayed on a computer screen approximately every half second. Participants were told to press a key as fast as possible whenever a 2, 5, or 8 appeared. This task as a good measure of visual attentional ability. 

Task 2: There were two sounds (one high and one low) played at random. Participants were told to press a key as fast as possible when hearing the designated sound. This task is a good measure of audio reaction time.

Here’s what happened…

Task 1: Attention

In the low stress group, there was a minor improvement (26%) at 60 minutes. 

In the high stress group, there was already a 39% improvement in the attentional task at 0 minutes after ingestion. This value steadily increased to a 56.6% improvement by 60 minutes! 

Task 2: Reaction Speed

In the low stress group, no change. This is consistent with previous literature showing, at best, no change in performance.

In the high stress group, reaction time improved from 15% to 20% as time went on. This is a huge change for this metric! Can you imagine doing something in 20% less time? Or having your brain go 20% faster?

My Thoughts

Yes, the old literature was down on L-theanine. But it doesn’t tell the whole story.

Stress and anxiety are detrimental to all sorts of tasks. We know that many professional athletes and performers are taking substances to steady their nerves (see beta blocker use in the news). 

If you’re living a high-stress life or engaging in high pressure situations where peak performance matters, then pre-emptively managing your anxiety can make sure your performance isn’t compromised. The athletes and performers wouldn’t be looking to use illicit substances otherwise.

L-theanine offers a nice alternative. It’s natural, safe, and legal. Not to mention, many of the classic anti-anxiety medications come with performance decreasing side effects – drowsiness, impaired concentration, and slowed reflexes. L-theanine doesn’t come with these downsides.


L-theanine, alone, will only enhance performance in situations where stress or anxiety are getting in the way. That being said, I think stressful situations come up far more frequently in real life than in a research study. 

There’s no need to take L-theanine daily. You’ll end up compromising your baseline performance levels. Be strategic with it. Take it before high-stress situations as needed. 

Ready to take your game to a whole new level?

Check out my advanced programs on Patreon for individualized guidance (and to support what I do).

While you’re at it, come join my Private Discord Server where you can find duo buddies who have the same fire you do to improve themselves (only invite me to duo if you are looking for a back workout). You are the average of the 5 people you hang out with, why not pick people who will push you to be better?


  1. Haskell CF, Kennedy DO, Milne AL, Wesnes KA, Scholey AB. The effects of L-theanine, caffeine and their combination on cognition and mood. Biol Psychol. 2008 Feb;77(2):113-22. doi: 10.1016/j.biopsycho.2007.09.008. Epub 2007 Sep 26. PMID: 18006208.
  2. Higashiyama A., Htay H.H., Ozeki M., Juneja L.R., Kapoor M.P. Effects of l-theanine on attention and reaction time response. J. Funct. Foods. 2011;3:171–181. doi: 10.1016/j.jff.2011.03.009.
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