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L-Tyrosine

The amino acid behind dopamine, thyroid hormones & melanin

Definition: What is L-Tyrosine?
How does your body produce L-Tyrosine?
What role does L-Tyrosine play in your body?
Precursor to Dopamine, Noradrenaline & Adrenaline
L-Tyrosine & Thyroid
L-Tyrosine & Melanin
L-Tyrosine & Cognitive Performance
Foods Containing L-Tyrosine
How Much L-Tyrosine Do You Need?
What to Consider When Taking It
Bibliography & Sources

Definition: What is L-tyrosine?

L-tyrosine is one of the 20 amino acids your body uses to build proteins. Unlike phenylalanine, for example, tyrosine is considered non-essential: your body does not necessarily need to obtain it from your diet because it can produce it itself.³ However, if phenylalanine metabolism is impaired, the body may be unable to produce tyrosine or may produce very little. In this case, tyrosine becomes conditionally essential and must be obtained from food.³ The “L” stands for the form your body can use. There is also a D-form, which also occurs naturally. And the name? It comes from the Greek word for cheese.

If you would like to delve deeper into the basics, you will find a good overview in our article What are amino acids and what do they do?.

How does your body produce L-tyrosine?

Your body has two sources of L-tyrosine: your diet and its own production. For production, it uses the essential amino acid L-phenylalanine. An enzyme called phenylalanine hydroxylase attaches a small hydroxy group to the phenylalanine – and tyrosine is formed. This happens mainly in the liver.³

Because the two amino acids are so closely related, their requirements are usually stated together in nutritional science (more on this under How much L-tyrosine do you need?).

The blood-brain barrier: How L-tyrosine enters the brain:

For L-tyrosine to be converted into neurotransmitters in the brain, it must first cross the blood-brain barrier . This protective barrier separates your brain from the bloodstream and only allows selected substances to pass through. L-tyrosine uses a transport system for this, which it shares with other large amino acids, for example with L-tryptophan and the branched-chain amino acids (BCAAs). Because this transporter is already well utilized even at normal blood levels, the amino acids compete for the available spots.¹⁶

Imagine a revolving door with several groups waiting in line: How much tyrosine enters the brain depends not only on its own concentration in the blood, but also on how many competitors are currently waiting in line. For example, if the concentration of BCAAs in the blood increases sharply, less tyrosine enters the brain. In animal studies, this also led to a decrease in the production of dopamine.¹⁶ L-tryptophan itself is, by the way, the precursor for another neurotransmitter: Serotonin.¹⁶

What role does L-tyrosine play in your body?

Of course, L-tyrosine is a perfectly normal amino acid. But here’s where it gets interesting: L-tyrosine is the precursor to several neurotransmitters and hormones that you probably already know.

Precursor for dopamine, norepinephrine & epinephrine

Imagine a kind of assembly line: It starts with L-tyrosine, which becomes L-DOPA, then dopamine, then noradrenaline, and finally adrenaline. This group of neurotransmitters is called catecholamines. The first step is carried out by the enzyme tyrosine hydroxylase. It is considered the bottleneck of the entire chain because it determines how quickly the supply flows.⁴

One peculiarity: For most neurotransmitters, it hardly matters how much precursor material is currently available. This is different with catecholamines. Here, their production in the brain also depends on how much tyrosine is available—but especially in nerve cells that are particularly active at the time.¹ So the assembly line doesn't simply run faster just because more material is ready. It also needs orders.

Nerve transmission of dopamine to receptors, signaling pathway, L-tyrosine

What are dopamine and norepinephrine known for?

Dopamine and norepinephrine are involved in attention, working memory, and the response to stress, among other things.⁵ That is precisely why research is interested in L-tyrosine.

You may know dopamine as the “happy hormone.” However, the nickname is not entirely accurate: More precisely, dopamine is primarily a neurotransmitter associated with motivation and reward. It signals to your brain when something goes better than expected and motivates you to do it again.¹⁹ It cannot be inferred from this that additional L-tyrosine makes you happier

Darstellung Dopamin wie es von den Rezepturen empfangen wird

L-Tyrosine and the Thyroid: Building Block of Thyroid Hormones

Your thyroid also uses tyrosine. In a large protein called thyroglobulin, tyrosine building blocks are combined with iodine. This produces the thyroid hormones thyroxine (T4) and triiodothyronine (T3).²

Important context: This does not mean that more L-tyrosine automatically means more thyroid hormones. The thyroid regulates its hormone production through its own control signals from the pituitary gland.²

Precursor for melanin

And one more task that you can even see: In the pigment cells of your skin and hair roots, the melanocytes, the pigment melanin is produced from L-tyrosine. The enzyme tyrosinase converts L-tyrosine into it in several steps, via the same intermediate step as with the neurotransmitters: L-DOPA.¹³ Tyrosinase needs copper for this, and copper contributes to normal hair pigmentation.¹⁴ How much brown-black eumelanin and yellowish-red pheomelanin you produce is primarily determined genetically and determines your skin and hair color.

A body-made parasol: The melanocytes pass their melanin on to the surrounding skin cells in small packages. There it lies like a parasol over the cell nucleus and intercepts part of the UV radiation.¹³

And gray hair? Over the years, the melanocytes in the hair roots become exhausted, and the hair grows back with less or completely without pigment. This is a natural, largely genetically controlled process.¹⁵ Whether additional L-tyrosine changes this is not proven.

Hair and Melanin Pigment in the Hair from L-Tyrosine

L-Tyrosine and Cognitive Performance: What Do Studies Show?

Most studies focus on one question: Can L-tyrosine help maintain mental performance when the brain is under particular strain? The idea behind this is that certain nerve cells consume more noradrenaline and dopamine under stress. L-tyrosine could help replenish these supplies.

An evaluation of several studies from 2015 yielded nuanced results. Positive effects were observed primarily in short, stressful, or highly mentally demanding situations. In contrast, the authors found little evidence of any benefit for physical performance in sports. Their conclusion: L-tyrosine appears to play a role primarily when the neurotransmitter system is intact but temporarily under heavy demand.⁵

Cold, training, working memory: What exactly was examined

Cold: 19 adults each spent 90 minutes in cold water twice. Before, they ate a bar with or without L-tyrosine. In the cold, everyone performed worse on a memory test. With L-tyrosine, however, they answered the questions correctly more often and needed less time to memorize the template.⁶

Military training: 21 cadets participated in a demanding one-week combat training. One group (10 people) drank a high-protein drink with 2 g of tyrosine five times a day, while the control group (11 people) drank a high-carbohydrate drink. The tyrosine group performed better on a memory task and a coordination task.⁷ Since the drink also contained protein, the effect cannot be attributed solely to tyrosine.

Differences between people: Not everyone reacts the same way. In one study, people with a specific variant of a dopamine receptor gene benefited significantly more from L-tyrosine than others.⁸

Sleep deprivation: In one study, adults worked through the night and were awake for more than 24 hours at the end. After six hours, half received L-tyrosine (150 mg per kilogram of body weight), while the other half did not. In the tyrosine group, performance declined less sharply on a coordination task and an attention task. The effect lasted about three hours.²⁰

Creativity: 32 adults drank orange juice with 2 g of L-tyrosine or without. With L-tyrosine, they performed better on tasks that required finding one suitable solution from several clues. In free idea generation, i.e., classic brainstorming, however, no difference was observed.²¹

And stress? These studies primarily measured whether performance is maintained despite stress. They do not show that L-tyrosine itself reduces the perception of stress. In the cadet study, for example, mood did not change.¹⁰

Which foods contain L-tyrosine?

L-tyrosine is found in practically all high-protein foods. Particularly good sources are:⁹

Cheese, especially hard cheese such as Parmesan
Soy and tofu
Meat and poultry
Fish
Eggs
Nuts and seeds, such as pumpkin seeds
Legumes such as lentils or beans

A nice side effect: Most of these foods also provide phenylalanine, from which your body can produce tyrosine itself. Animal studies also show that a high-protein meal increases tyrosine levels in the brain.¹

How much L-tyrosine do you need?

Neither the German Nutrition Society nor the European Food Safety Authority has established its own reference value for L-tyrosine. The World Health Organization specifies the combined requirement for phenylalanine and tyrosine in adults as 25 mg per kilogram of body weight per day.¹⁰ For a body weight of 65 kg, this amounts to around 1.6 g for both amino acids combined.

Study quantities are not a recommendation

Significantly larger amounts were used in the studies described above: 300 mg per kilogram of body weight in the cold exposure study and 10 g per day in combat training.⁶,⁷ For a 65 kg person, that would be just under 20 g in the cold exposure study. These amounts show under what conditions the research was conducted. They are not suitable as a recommendation for daily intake. Dietary supplements are deliberately kept well below this.

What do safety assessments say?

The data on this is not yet consistent. In 2016, the Norwegian Scientific Committee for Food Safety (VKM) assessed daily intakes of 1,250 to 2,000 mg of L-tyrosine from dietary supplements and concluded that these amounts could pose a risk of adverse effects.¹¹ A more recent study from Japan examined 30 healthy men who took up to 4 g of L-tyrosine daily for four weeks. No unusual blood test results were observed, and complaints did not occur more frequently than during the comparison period without tyrosine.¹² However, women were not included in this study, and data on long-term intake are still lacking.

For you, this means: Stick to the recommended intake on the package and do not exceed it.

What should you pay attention to when taking L-tyrosine?

Timing: In the studies, L-tyrosine was usually taken shortly before the demanding situation, not continuously throughout the day.⁵,⁶

Keep an eye on multiple products: L-tyrosine is not only found in individual products, but also in many complexes. If you combine several dietary supplements, add up the amounts.

What to look for when buying: L-tyrosine for dietary supplements can be obtained through fermentation. During fermentation, microorganisms produce the amino acid from plant-based raw materials such as sugar.¹⁷,¹⁸ In addition, there are other manufacturing methods, such as chemical processes.¹⁸ If you live vegan, look for a corresponding label when buying. Also check whether the products contain the L-form and how much L-tyrosine is stated per daily serving. And if you are building up a supply, store the products in a dry, cool place away from light.

Combination with BCAA: As described with the blood-brain barrier, L-tyrosine and branched-chain amino acids compete for the same transporter.¹⁶ If you use BCAA products, for example in sports, it is therefore advisable not to take both at the same time.

Pregnancy and breastfeeding: There is insufficient safety data and information for pregnant and breastfeeding women. During this time, L-tyrosine is not suitable as a dietary supplement.¹¹,¹²

Medication and thyroid: L-tyrosine is a building block of thyroid hormones. As described above, however, more L-tyrosine does not automatically mean more thyroid hormones.² However, how additional intake affects a thyroid condition or when taken with thyroid hormones has hardly been studied. Therefore, speak with your doctor or pharmacist beforehand. This also applies if you regularly take medication, especially MAO inhibitors.

Conclusion: L-Tyrosine at a glance

L-tyrosine is an amino acid that your body can produce on its own from phenylalanine and obtain from high-protein foods. It is the precursor for dopamine, norepinephrine, and epinephrine, as well as your thyroid hormones. Research on L-tyrosine primarily focuses on its effects on cognitive performance during short periods of intense stress. However, the studies are small, the doses used are high, and no definitive conclusions can be drawn for everyday use. If you want to supplement with L-tyrosine, stick to the recommended intake and consult your doctor beforehand if you are taking medication or have thyroid-related concerns.

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L-Tyrosine

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Table of Contents

Definition: What is L-tyrosine?

How does your body produce L-tyrosine?

The blood-brain barrier: How L-tyrosine enters the brain:

What role does L-tyrosine play in your body?

Precursor for dopamine, norepinephrine & epinephrine

What are dopamine and norepinephrine known for?

L-Tyrosine and the Thyroid: Building Block of Thyroid Hormones

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Precursor for melanin

L-Tyrosine and Cognitive Performance: What Do Studies Show?

Cold, training, working memory: What exactly was examined

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How should these results be interpreted?

Which foods contain L-tyrosine?

How much L-tyrosine do you need?

Study quantities are not a recommendation

What do safety assessments say?

What should you pay attention to when taking L-tyrosine?

Conclusion: L-Tyrosine at a glance

More blog articles on this topic

Serotonin & 5 HTP: How do the substances work?

Repairing and protecting the blood-brain barrier

Understanding Stress Eating & Cravings: Causes, Biochemical Processes, and How to Break the Cycle

What are amino acids and what do they do?

Problems falling asleep? Causes and tips for falling asleep

Self-care ideas instead of stress: Let the year end with peace, energy and clarity.

Naturally Boost Testosterone: Do's & Don'ts for Balanced Testosterone

Heart health through Omega-3: Everything you should know about the benefits and correct dosage.

Strengthen a weak heart: Tips and natural remedies for your heart

Amino acids & sport: why you need protein building blocks

Amino acid deficiency: symptoms, causes and what you can do about it

More power through smart amino acids – new scientific perspectives

Creatine for muscle building: How effective is it really for your training?

Phenylalanine

L-Arginine

Glycine

magnesium

Silicium

Calcium

Tryptophane

Bibliography & Sources