L-Tyrosine: Benefits, Dosage, Side Effects, and More

As interest in the subject of nootropics (AKA smart drugs) continues to grow here in the U.S., and around the world, several different substances have burst onto the mainstream.

Amongst them, L-tyrosine has become especially popular, now being featured in dozens of different dietary supplements. But what does the science have to say about the benefits of l-tyrosine? Can it really help improve the function and performance of your brain?

On top of exploring the benefits of l-tyrosine, we'll also be looking at potential side effects, as well as going over dosage information. However, before we dive into all of that, lets, first discuss what l-tyrosine actually is and what roles it plays within the human body.

What is L-Tyrosine?

L-tyrosine is a non-essential amino acid that plays an important role in the synthesis of dopamine, epinephrine, and norepinephrine -- all-natural, biologically active compounds known as catecholamines.⁽¹⁾

Catecholamines function both as neurotransmitters and hormones, helping to maintain equilibrium throughout your brain and entire nervous system.⁽²⁾

Research shows that elevated levels of l-tyrosine help to trigger an increase in the production of dopamine (and other neurotransmitters) in your brain, which can become depleted by both mental and physical stress.⁽³⁾⁽⁴⁾

Adequate levels of catecholamines like dopamine are ultimately required in order to support and maintain normal brain function. 

As neurotransmitters, catecholamines facilitate the transmission of information to cells all throughout your body, helping to manage and coordinate their actions.⁽⁵⁾

As a precursor to neurotransmitters like dopamine, l-tyrosine ultimately plays an important role in the regulation of several neurological processes, and as such, its effects on cognition and mental performance have been extensively researched.  

What Are The Benefits of L-Tyrosine?

To date, there is a sizeable body of evidence that L-tyrosine supplementation may help to improve several aspects of your mental functioning, especially during cognitively demanding tasks.^(6)(7)(8)

From improving your memory to enhancing your out-of-the-box thinking, several positive associations have been made between L-tyrosine supplementation and mental performance.  

These positive effects have been attributed to L-tyrosine’s ability to prevent the depletion of available catecholamines under stress -- stressful situations can drain your brain’s supply of dopamine (and other substances), imping on higher mental functions like your memory and attention.⁽⁹⁾

Although, it is important to point out that while there appears to be a substantial body of evidence for some of the cognitive benefits associated with L-tyrosine, there are still mixed findings when it comes to others.  

Benefit #1: L-Tyrosine Can Enhance Memory

A number of different human trials involving healthy subjects have investigated the effects of L-tyrosine on working memory during stress exposure and to date, most studies have demonstrated positive results.  

For Example, a 2013 double-blind, placebo-controlled study investigated the effects of L-tyrosine supplementation on participants’ mental performances.⁽¹⁰⁾

In two different sessions, separated by three to seven days, participants were given both an L-tyrosine supplement and a placebo and asked to participate in a series of cognitively demanding tasks designed to test their working memory.  

The findings from the trial demonstrate that participants, on average, saw significant improvements in their test performances when they were given L-tyrosine, leading the researchers to conclude that the stimulation of dopamine pathways via L-tyrosine supplementation had a positive effect on subjects’ working memory.  

Other research, like a 2017 study published in Psychological Research, for example, has also found a positive effect of L-tyrosine supplementation on episodic memory.⁽¹¹⁾

Episodic memory refers to the process through which you remember specific events -- everybody’s episodic memory is unique, which is why different people’s recollection of the same event can vary.  

in the aforementioned study, the researchers ultimately found that taking an L-tyrosine supplement beforehand helped to significantly improve the performance of subjects on a standardized episodic memory test.  

Benefit #2: It Can Improve Creativity and Deep Thinking

On top of potentially improving several aspects of your memory, some research also suggests that L-tyrosine may help to improve your creativity and deep thinking as well. 

For example, a 2014 double-blind, placebo-controlled study involving healthy adults investigated the effects of L-tyrosine supplementation on divergent thinking.⁽¹²⁾

In two different sessions, separated by seven days, participants were given both a placebo and L-tyrosine supplement and asked to perform a series of cognitively demanding tasks. 

At the conclusion of the study, the researchers ultimately found that when subjects were given L-tyrosine, they performed significantly better on tasks requiring them to think creatively in order to come up with a solution to the problem with which they were presented.  

Benefit #3: L-Tyrosine Can Strengthen Cognitive Flexibility

Other research involving L-tyrosine has also demonstrated that it may help to improve cognitive flexibility, which is a measure of the brain’s ability to shift its focus from one task to another -- picture transitioning from thinking about the size of a particular object to its color.  

For instance, a 2015 study published in Neuropsychologia recruited 22 healthy adults to participate in a double-blind, placebo-controlled trial investigating the effects of L-tyrosine on cognitive control.⁽¹³⁾

Using a well-established task-switching paradigm, researchers evaluated participants’ cognitive flexibility with and without the aid of an L-tyrosine supplement.  

The data from the study ultimately demonstrated that when participants were given L-tyrosine, they were able to switch between tasks more efficiently in comparison to when given only a placebo. 

The researchers ultimately concluded that L-tyrosine may be a useful cognitive enhancer, especially when it comes to the mental processes related to multi-tasking.   

Other Potential Benefits of L-Tyrosine

⫸L-Tyrosine and Mood

Because dopamine and norepinephrine are indirect regulators of your mood, some researchers hypothesize that L-tyrosine -- a precursor to these neurotransmitters -- may help to improve your mental state.⁽¹⁴⁾

And indeed, some research has demonstrated a positive effect.  For instance, a 2006 study involving 2 well-established anti-depressant efficacy tests found that regular tyrosine supplementation helped to significantly improve participants’ depressive symptoms.⁽¹⁵⁾

However, there are mixed findings when it comes to its efficacy.  While some research has demonstrated positive results, other trials failed to find any effect of L-tyrosine supplementation on mood. 

One 2011 review on the subject ultimately concluded that evidence for the regular use of L-tyrosine as an effective treatment for depression is limited.⁽¹⁶⁾

⫸Exercise Performance and L-Tyrosine

There is some evidence that L-tyrosine may also enhance exercise performance, however, the findings are mixed as well.  When it comes to endurance exercise, in particular, some research suggests that maintaining sufficient dopamine levels in the brain may help to improve motivation, which in turn, may bolster performance.⁽¹⁷⁾

For example, a 2011 randomized, double-blind study published in the European Journal of Applied Physiology examined the effects of L-tyrosine supplementation on subjects performing a moderate-intensity cycling exercise to exhaustion.⁽¹⁸⁾

At the conclusion of the study, researchers found that, on average, subjects who received a dose of L-tyrosine prior to exercising lasted longer before they reached exhaustion compared to those who were given only a placebo (19.7 min vs. 14 min).  

It is important to point out though that some other studies failed to find a positive effect of L-tyrosine on exercise performance.⁽¹⁹⁾

However, researchers speculate, that L-tyrosine may only help to improve performance when the exercise is cognitively demanding enough. A 2015 review ultimately concluded that most studies that failed to find any positive effects involved exercises that didn’t sufficiently tap into participants’ mental processes.⁽²⁰⁾

L-Tyrosine Sources

L-tyrosine can be obtained directly from dietary sources -- particularly from high-protein foods like beef, fish, chicken, turkey, nuts, seeds, milk, cheese, soybeans, and tofu.  

Your body can also synthesize it from the amino acid phenylalanine, which also predominantly comes from protein-based food sources like those mentioned above.

On top of being found in the foods you eat, L-tyrosine is also available as a dietary supplement and can be taken both on its own and in combination with other nootropics to further enhance it cognitive effects.  

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L-Tyrosine Side Effects and Safety

L-tyrosine has been generally recognized as safe by the FDA.⁽²¹⁾ It is well tolerated in most healthy individuals and no serious side effects or safety concerns have been reported when moderate dosages were used.  

With that being said, one study did find that those on low-protein diets (< 10% total energy intake) may be at an increased risk of experiencing negative side effects with regular l-tyrosine supplementation.⁽²²⁾

It can also potentially cause unwanted interactions with certain medications, such as those related to blood pressure, thyroid hormones, and hypertension, so you’ll need to talk to your doctor before beginning l-tyrosine supplementation if you’re taking other drugs.  

L-Tyrosine Dosage Recommendations

The World Health Organization suggests that a daily L-carnitine intake of 14 mg per kilogram of body weight is sufficient to meet your body’s normal requirements.⁽²³⁾

However, when it comes to maximizing its effects as a supplement, there has yet to be a general consensus as to exactly how much L-carnitine you should take per day.  The dosages used in human trials vary significantly -- from less than a gram all the way up to over 10 grams per day.⁽²⁴⁾

• References
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  2. “Physiology, Catecholamines”Paravati, S., Warrington, S.J. StatPearls. Jan. 2020.
  3. “Eating to stop: Tyrosine supplementation enhances inhibitory control but not response execution”Colzato, L.S., Jongkees, B.J., Sellaro, R., van den Wildenber, W.P.M., Hommel, B. Neuropsychologia. Sep. 2014.
  4. “Tyrosine, Phenylalanine, and Catecholamine Synthesis and Function in the Brain”Fernstorm, J.D., Fernstorm, M.H. The Journal of Nutrition. Jun. 2007.
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  7. “Behavioral and cognitive effects of tyrosine intake in healthy human adults”Hase, A., Jung, S.E., het Rot, M. Pharmacology Biochemistry and Behavior. Jun. 2015.
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  12. “Food for creativity: tyrosine promotes deep thinking”Colzato, L.S., de Haan, A.M., Hommel, B. Psychological Research. Sep. 2014.
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  21. “CFR - Code of Federal Regulations Title 21”U.S. Food and Drug Administration. Apr. 2019.
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