What is L-Theanine?

L-theanine is a naturally-derived amino acid that can be found in tea leaves.  It’s mood-stabilizing properties have been known for centuries and it has been thoroughly studied ever since it was first isolated back in the 1940s. (1)

On its own, l-theanine has a calming effect, helping to produce a relaxed, clear state of mind; however, when mixed with caffeine its effects change significantly, which we’ll get into more below.    

The FDA categorizes l-theanine as a generally recognized as safe (GRAS) substance, meaning that most qualified experts believe there to be little danger involved in taking it as it’s intended.  In recent years it’s become a popular dietary supplement amongst everyone from cross-fitters to long-distance runners.                  

What Does L-Theanine Do?

L-theanine is classified as a nootropic substance, which basically means that it alters the way in which your brain works.  More specifically, one of the primary ways in which it functions is by boosting your body’s production of mood-stabilizing neurotransmitters like serotonin and dopamine. (2)

Neurotransmitters are chemical messengers that travel within your body, allowing neurons and cells to communicate with each other.   Increasing your body’s production of chemicals like serotonin and dopamine ultimately helps to promote feelings of well-being and relaxation.  

On top of boosting your body’s production of certain neurotransmitters, l-theanine is also believed to affect your brainwaves.  Your brainwaves actually shift between a range of different frequencies, with some frequencies producing different mental states than others.  

More precisely, l-theanine is believed to boost alpha brain waves, which have been associated with a calm, relaxed state of mind. (3)(4)

L-Theanine in Human Trials

A number of studies have demonstrated a positive relationship between l-theanine and stress relief.  For example, a 2007 double-blind study published in the Journal of Biological Psychology recruited 12 individuals to take part in four different experimental trials. (5)

In two of the trials, participants were administered l-theanine, while the other two trials were controls — in one, participants received a placebo and the other they received nothing at all.  

The researchers ultimately found that l-theanine significantly reduced a number of measurable stress responses in the study participants.  Both participants’ heart rates and salivary immunoglobulin responses — both acute stress responses — were significantly lower compared to the control conditions.    

Another 2011 double-blind study published in the Journal of Functional Foods also found significant anti-stress effects associated with l-theanine intake. (6)  The researchers recruited 18 healthy college students. Participants received both a 200mg dose of l-theanine and then, later on, a placebo.  

Like in the aforementioned trial, the researchers in this study also found that l-theanine significantly decreased participants’ heart rates, particularly amongst high-anxiety individuals.  On top of that, the study also demonstrated a significant relationship between l-theanine supplementation and increased alpha brainwaves, which again, are associated with feelings of relaxation.  

L-Theanine’s Nootropic Benefits Change When Mixed With Caffeine

While l-theanine may help to alleviate stress when taken on its own, its effects become significantly altered when mixed with caffeine. 

Being the most popular psychoactive substance on the planet, caffeine needs little introduction: it’s the energy-boosting ingredient found in coffee, tea, and all sorts of dietary supplements.  

Once combined with caffeine, l-theanine helps to amplify its effects,  improving cognitive functions like reaction time and alertness to a greater degree than caffeine alone. (7)(8)

For example, a 2008 placebo-controlled, double-blind study published in the Journal of Biological Psychology investigated the effects of l-theanine and caffeine on a range of cognitive tasks. (9)

Participants went through four trials.  In trial one, they received only caffeine. For trial two, participants were given only l-theanine. In trial three, they received both caffeine and l-theanine and in the final trial they were given only a placebo.  

The researchers ultimately found that caffeine helped to improve reaction time and information processing all on its own; however, when combined with l-theanine, participants on average performed even better on tests related to reaction time, working memory, and sentence verification accuracy.          

Another study published in the Journal of Nutritional Neuroscience recruited 27 participants to investigate the combined effects of l-theanine and caffeine. (10) Over the course of the study, participants received a placebo, one 50 mg dose of caffeine, and one 50mg dose of caffeine plus 100 mg of l-theanine. There was a 7-day “wash out” period before participants took each substance.

The researchers ultimately found that caffeine on its own helped to improve participants’ subjective alertness as well as their ability to perform attention-switching tasks when compared to the placebo.  

The results for the caffeine and l-theanine combination were even better.  On top of observing greater improvements in alertness and attention-switching, researchers also saw significant improvements in memory-related tasked when l-theanine was paired with caffeine.    

L-Theanine Dosing Recommendations

While dosage recommendations for l-theanine do vary, 100 mg per day was the most commonly administered dose in both clinical and experimental studies.    Long story short, somewhere between 100 mg – 200 mg daily should be the ideal range for most people to feel the effects.

Wrap Up

L-theanine is a naturally derived amino acid that has become popular as a dietary supplement in recent years.  Several studies have shown that on its own, l-theanine has stress-reducing effects, helping to produce a calm, relaxed state of mind.

On top of that, there is also a sizeable body of evidence that l-theanine helps to boost the effects of caffeine when taken in tandem.  Several studies have demonstrated that the combination of l-theanine and caffeine increases things like reaction time and alertness to a greater degree than caffeine alone.