Clinical uses of L-tyrosine in naturopathic medicine

Are you a healthcare provider? Read our research summary of L-Tyrosine on Naturopathic Pediatrics PRO, our website for professionals.

What is Tyrosine and what is it used for?

L-Tyrosine, commonly referred to as just tyrosine, is a conditionally essential amino acid that the body makes from another amino acid, phenylalanine. Tyrosine is essential for the production of a family of neurotransmitters called catecholamines that includes epinephrine, norepinephrine, and dopamine.¹ Neurotransmitters are cell messengers that send signals from neurons to other cells in the body and in this case, play a role in mood regulation, memory, and alertness. Additionally, tyrosine is a precursor to thyroid hormone and melanin synthesis.¹

Recommended Dietary Allowance (RDA) for Tyrosine

Technically, there isn’t an RDA established for tyrosine and most people meet their needs by eating a variety of protein rich foods. In specific instances, supplementation may be necessary. Most studies utilize a dose of 100-150 milligrams per one kilogram of body weight in adults, but this varies for children and individuals with phenylketonuria.¹ It is best practice to take tyrosine supplements on an empty stomach since other amino acids may interfere with its absorption.

Food Sources of Tyrosine

Tyrosine can be found in a variety of animal and plant foods, including almonds, avocado, banana, beef, dairy, eggs, fish, lima beans, and soy products.¹

Signs of Tyrosine Deficiency

Tyrosine is considered conditionally essential because it’s made from the amino acid phenylalanine. When adequate phenylalanine is consumed from the diet, the body readily converts it to tyrosine. Therefore, a dietary deficiency in phenylalanine may lead to insufficient tyrosine.

The most common cause of a phenylalanine deficiency is the disorder of amino acid metabolism called phenylketonuria (PKU). People with PKU can’t break down phenylalanine, allowing it to build up in the body and accumulate in the bloodstream. Too much phenylalanine can be toxic to the nervous system and result in intellectual and developmental disabilities. The primary intervention for PKU is limiting foods containing phenylalanine which includes all high protein foods and may lead to a tyrosine deficiency.

Another risk factor for tyrosine deficiency is excess stress since prolonged periods of stress open the floodgates of catecholamines and over time, lead to their depletion. Some studies suggest that supplemental L-tyrosine can attenuate this response. Symptoms of a deficiency include hypothyroidism, low blood pressure, fatigue, learning and behaviors disorders, and depression.

Signs of Tyrosine Excess

Excess tyrosine typically results from high-dose supplementation or a metabolic block in its conversion pathways. Symptoms include:

• Anxiety or agitation
• Nausea or headache
• Brain fog
• Heartburn
• Signs of hyperthyroidism

Clinically, some patients with COMT or MAOA SNPs may be more sensitive to tyrosine and experience overstimulation.

Safety of L-tyrosine

L-tyrosine supplements are generally recognized as safe by the FDA, but may interact with medications such as Levodopa, monoamine oxidase inhibitors, and thyroid hormones Studies on long term tyrosine use are not robust enough to draw any conclusions. As always, supplements should only be considered under the supervision of a medical provider.

What is the difference between tyrosine and L-tyrosine?

L-tyrosine specifically refers to the natural form of the amino acid, and the “L” designation indicates the specific stereochemistry of the molecule. In organic chemistry, molecules can exist in different forms called enantiomers, which are mirror images of each other. The L- and D- prefixes are used to distinguish between the two enantiomers. The best way of describing this is to say that molecules have different “handedness,” just as our right and left hands are identical, but are mirror forms of one another. The L-form is the biologically active form that is used in protein synthesis and various biochemical reactions in the body.

Stress Response

L-tyrosine plays a central role in supporting the body’s ability to cope with physical stress by replenishing catecholamines. These neurotransmitters—especially dopamine and norepinephrine—can become depleted in response to prolonged stress, such as extreme cold, high altitude, or sleep deprivation. Studies in both animals and humans suggest that supplementing with L-tyrosine helps preserve cognitive function in these conditions. Tyrosine appears to work best when the brain is under stress and catecholamine activity is heightened, rather than in baseline or non-stressful environments.

It’s important to clarify that while tyrosine is sometimes marketed as a stress reliever, it is most effective in physical or environmental stress, not necessarily emotional or psychological stress. For example, tyrosine may help a teenager cope with jet lag or a sleep-deprived schedule more than daily social anxiety.

Fatigue

Fatigue—especially mental fatigue—may be linked to low levels of catecholamines. Tyrosine supplementation has been shown to improve alertness and reduce mental fatigue during sleep deprivation and periods of intense cognitive demand. In a study of adults who missed a night of sleep, tyrosine supplementation improved psychomotor performance and attention. Rather than acting as a stimulant, tyrosine helps the brain work more efficiently when energy and focus are compromised.

Depression

Because tyrosine is a precursor to dopamine and norepinephrine, it has been investigated as a possible support in depression. Animal studies show improvement in stress-induced depressive behaviors after tyrosine supplementation. Some human studies report improvements in mood and apathy when tyrosine and phenylalanine are restricted, further emphasizing their importance in neurotransmitter balance.

However, research in humans remains mixed. Some trials show little or no benefit for tyrosine in treating major depression. Clinically, I find tyrosine most useful for patients with mixed fatigue and mild depressive symptoms, rather than classic depression involving anhedonia, insomnia, or anxiety. For those patients, serotonergic support is typically more effective.

Mental Clarity and Cognitive Performance

L-tyrosine is well-documented for enhancing cognitive function under pressure. In tasks that require multitasking, working memory, decision-making, and flexibility, tyrosine helps replenish neurotransmitter stores and supports executive function. Research shows that tyrosine supplementation can buffer the negative cognitive effects of stress, sleep loss, and cognitive overload—making it especially helpful for students or teens navigating academically intense periods or standardized testing.

Tyrosine does not “boost” cognition beyond baseline, but it helps maintain performance when the brain is taxed. Think of it like refueling the brain’s supply of chemical messengers when they’re running low during stress.

Summary

Tyrosine is a critical amino acid involved in the production of neurotransmitters, thyroid hormones, and melanin. While most people get enough from food, supplementation may be helpful during periods of intense stress, fatigue, or for certain medical conditions like PKU.

L-tyrosine supplements are safe when used appropriately but may cause overstimulation in sensitive individuals. I recommend using them cautiously in children age 8 and older, and always under medical supervision.

Tyrosine may support:

• Mental clarity
• Stress resilience
• Alertness during sleep deprivation
• Mood regulation (with fatigue-driven depression)

Disclaimer: This article is for educational purposes only and does not substitute for medical advice. Always consult your healthcare provider before starting new supplements.

References:

1. Zakkaria L. Amino Acids. University of Bridgeport. 2022.
2. Cleveland Clinic. Should You Try an L-Tyrosine Supplement? A Look at Its Benefits and Side Effects. Healthessentials. 2023.
3. Young SN. L-tyrosine to alleviate the effects of stress?. J Psychiatry Neurosci. 2007;32(3):224.
4. C. ter Borg PC, Fekkes D, Vrolijk JM, van Buuren HR. The relation between plasma tyrosine concentration and fatigue in primary biliary cirrhosis and primary sclerosing cholangitis. BMC Gastroenterol. 2005;5:11. Published 2005 Mar 24. doi:10.1186/1471-230X-5-11
5. Neri DF, Wiegmann D, Stanny RR, Shappell SA, McCardie A, McKay DL. The effects of tyrosine on cognitive performance during extended wakefulness. Aviat Space Environ Med. 1995;66(4):313-319.
6. Alabsi A, Khoudary AC, Abdelwahed W. The Antidepressant Effect of L-Tyrosine-Loaded Nanoparticles: Behavioral Aspects [published correction appears in Ann Neurosci. 2019 Jan;25(3):141-151]. Ann Neurosci. 2016;23(2):89-99. doi:10.1159/000443575
7. McLean, A., Rubinsztein, J.S., Robbins, T.W.et al. The effects of tyrosine depletion in normal healthy volunteers: implications for unipolar depression. Psychopharmacology 171, 286-297 (2004).
8. Gelenberg AJ, Wojcik JD, Falk WE, et al. Tyrosine for depression: a double-blind trial. J Affect Disord. 1990;19(2):125-132. doi:10.1016/0165-0327(90)90017-3
9. Steenbergen L, Sellaro R, Hommel B, Colzato LS. Tyrosine promotes cognitive flexibility: evidence from proactive vs. reactive control during task switching performance. Neuropsychologia. 2015;69:50-55. doi:10.1016/j.neuropsychologia.2015.01.022
10. Hase A, Jung S, Rot M. Behavioral and Cognitive Effects of Tyrosine Intake in Healthy Human Adults. Pharmacology Biochemistry and Behavior. 2015;133:1-6
11. Colzato LS, Jongkees BJ, Sellaro R, Hommel B. Working memory reloaded: tyrosine repletes updating in the N-back task. Front Behav Neurosci. 2013;7:200. Published 2013 Dec 16. doi:10.3389/fnbeh.2013.00200