L-Tyrosine: Health Effects and Safety

Answer:

What Is L-Tyrosine

L-tyrosine is an amino acid produced by the body from the amino acid phenylalanine (Ubaldi, Int J Mol Sci 2023; Hafid, Transl Pediatr 2015). Since it is made by the body, it is not essential.

L-tyrosine functions as a precursor of catecholamines, a group of stress-response hormones including dopamine and norepinephrine (Attipoe, Mil Med 2015; McCann, Neuropsychopharmacology 1993). L-tyrosine also serves as a precursor of melanin, a natural pigment responsible for hair, skin and eye color (Rzepka, Postepy Hig Med Dosw (Online) 2016). L-tyrosine is also used by the body to make the thyroid hormones thyroxine and triiodothyronine (Rivlin, Am J Med 1966).

In addition to the "L" form, tyrosine also exists in the "D" form. However, unlike the "L" form, the "D" form of tyrosine has been shown to depress growth in mice (Friedman, Amino Acids 2012). Consequently, based on this anti-nutritive effect of D-tyrosine, dietary supplements contain only L-tyrosine, which may just be referred to as just "tyrosine." In this article, the term "tyrosine" always refers to L-tyrosine.

Health Effects of L-Tyrosine

Based on its functions in the body, tyrosine has been evaluated for conditions including physical and mental stress, phenylketonuria (PKU), depression, and attention deficit-hyperactivity disorder (ADHD), although clinical studies have shown its benefits to be limited, at best, as explained below.

Stress

Prolonged stress can deplete body levels of catecholamines, a group of stress-response hormones, and this depletion can lead to decreased alertness, worsened mood, and impaired physical or cognitive performance. Since L-tyrosine serves as a precursor to catecholamines, it has been evaluated for reducing these effects of catecholamine deficiency (Attipoe, Mil Med 2015; McCann, Neuropsychopharmacology 1993). Clinical studies suggest that L-tyrosine may slightly improve cognitive function during mental stress, although results are mixed. It does not seem to improve physical performance during physical stress.

Psychological Stress

A study among 22 young women (average age 20) showed that taking a single 2,000-mg dose of L-tyrosine dissolved in 400 mL (13.5 fl. oz) of orange juice one hour before a mentally demanding cognitive test slightly improved accuracy by about 5% compared to placebo. However, there was no benefit on cognition for less mentally demanding tasks (Colzato, Front Behav Neurosci 2013). A similar study among 22 healthy young females (19 years old) showed that taking the same dose of L-tyrosine dissolved in orange juice one hour before a completing a mentally demanding cognitive test slightly improved the speed at which a participant could switch between different tasks, a measure of cognitive flexibility, compared to placebo (Steenbergen, Neuropsychologia 2015).

On the other hand, a study among 80 young men and women (average age 21) showed that taking 2,000 mg of L-tyrosine powder 40 minutes before participating in a mental stress challenge (i.e., a two-minute virtual reality active shooter drill) did not significantly improve most measures of cognitive function, nor did it lessen the increases in heart rate, salivary alpha-amylase levels (an enzyme in the saliva that increases in response to stress), or anxiety compared to placebo (McAllister, Stress 2024).

Physical stress

Taking tyrosine before endurance exercise or exercising in heat does not significantly improve endurance, muscle strength or anaerobic power compared to placebo (Tumilty, Med Sci Sports Exerc 2014; Watson, Int J Sport Nutr Exerc Metab 2012; Sutton, Int J Sport Nutr Exerc Metab 2005; Chinevere, J Appl Physiol (1985) 2002; Struder, Horm Metab Res 1998).

Phenylketonuria (PKU)

People with phenylketonuria (PKU) are not able, or have only limited ability, to convert the amino acid phenylalanine to tyrosine. Consequently, people with this condition must follow a low phenylalanine diet to avoid excess buildup of phenylalanine, which can cause neurological complications such as brain damage (Ubaldi, Int J Mol Sci 2023; Hafid, Transl Pediatr 2015). Although people with PKU are often advised to take protein supplements fortified with tyrosine to avoid becoming deficient in this amino acid (Ubaldi, Int J Mol Sci 2023), there does not appear to be any evidence that taking additional tyrosine alone improves intelligence, growth, nutritional status, quality of life or lifespan among people with PKU (Remmington, Cochrane Database Syst Rev 2021).

Depression

Depression has been linked with low levels of the catecholamine norepinephrine. Since L-tyrosine is a precursor to this catecholamine, it has been speculated that L-tyrosine supplementation may improve symptoms among people with major depression. However, a clinical study found that taking L-tyrosine (about 7,000 mg daily) for one month did not improve depression symptoms despite increasing blood levels of tyrosine compared to placebo (Gelenberg, J Affect Disord 1990).

For information about other supplements for depression, see our article, "What are the best supplements for depression and anxiety?"

Attention Deficit-Hyperactivity Disorder (ADHD)

Tyrosine supplementation has been promoted for improving symptoms of ADHD, but clinical evidence does not seem to support this use. Children with ADHD do not appear to have abnormal blood or urinary levels of L-tyrosine, and blood levels of tyrosine do not appear to be linked with ADHD symptom severity (Bergwerff, PLoS One 2016). Although one study showed positive outcomes when children with ADHD were treated with a combination of 5-HTP and L-tyrosine for 8 to 10 weeks (Hinz, Neuropsychiartr Dis Treat 2011), the study was later retracted due to concerns raised by the publisher (No Author, Neuropsychiatr Dis Treat 2020).

Side Effects and Safety of L-Tyrosine

L-tyrosine (as well as DL-tyrosine) is generally recognized as safe (GRAS) by the FDA (Code of Federal Regulations, 2/25/25). Taking 1 to 4 grams (1,000 to 4,000 mg) of L-tyrosine daily on a short-term basis (four weeks) was generally well tolerated in a study in Japan among 20 healthy men (average age 43). Compared with placebo, L-tyrosine caused no significant changes in blood pressure, heart rate, blood sugar, cholesterol and triglyceride levels, electrolytes, or markers of kidney and liver function. Mild to moderate side effects — including fatigue, headache, gastrointestinal symptoms, and respiratory infection — were more common with L-tyrosine than with placebo but were not more frequent with higher doses (i.e., those closer to 4 grams) (Matsumoto, Nutrients 2026).

Tyrosine is converted to tyramine by the body. Monoamine oxidase inhibitors (MAOIs), a class of antidepressant medications, can prevent the breakdown of tyramine, which can lead to sudden increases in blood pressure. Concern has been raised that combined intake of tyrosine along with MAOIs may lead to tyramine accumulation and corresponding high blood pressure (i.e., "hypertensive crisis") (Hinz, Clin Pharmacol 2014). However, there do not appear to be confirmed cases of hypertensive crisis due to combined intake of L-tyrosine and an MAOI, and one case report showed that concomitant intake of an MAOI (selegiline) along with parental nutrition containing tyrosine did not result in adverse effects (Bharani, Eur J Clin Nutr 2024). Nevertheless, you should talk to your doctor before taking tyrosine if you already take an MAOI such as isocarboxazid (Marplan), phenelzine (Nardil), tranylcypromine (Parnate) or selegiline.

Tyrosine should be used cautiously or avoided by people taking thyroid hormones, or by those with hyperthyroidism or Graves' disease. Tyrosine is a precursor to thyroid hormones (Rivlin, Am J Med 1966), and one clinical study showed that taking 12 grams of tyrosine per day during the winter reduced levels of thyroid stimulating hormone by about 30% and increased levels of free triiodothyronine, a thyroid hormone by 6%, compared to baseline, and these changes were significant compared to placebo (Palinkas, Int J Circumpolar Health 2007).

Taking the Parkinson's disease medication L-Dopa along with L-tyrosine may reduce the absorption of L-tyrosine (Wade, Nature 1973). It seems prudent to separate dosing by several hours to avoid this effect.

Some tyrosine supplement labels warn people with a history of malignant melanoma to consult a healthcare professional before use. This is likely a theoretical concern because tyrosine is a chemical precursor to melanin, which is normally produced in melanocytes. However, it is not clear if taking tyrosine would cause or stimulate melanocyte malignancy. Similarly, although it has been tried, it is not clear if reducing tyrosine (and phenylalanine) in the diet reduces melanoma growth (Lawson, AJCN 1985; Demopoulos, Cancer 1966).

Getting Tyrosine from Food?

Clinical studies typically use a daily dose of 2,000 mg of tyrosine (Steenbergen, Neuropsychologia 2015; Colzato, Front Behav Neurosci 2013). While it is possible to get that much tyrosine from foods, it would require multiple servings, as shown in the graph below. For example, cooked Atlantic salmon contains about 602 mg of tyrosine in standard 3 oz serving, so you would need 3.3 servings to get 2,000 mg (FoodData Central, 9/22/26).

Foods Rich in Tyrosine
(Servings needed to get 2,000 mg of tyrosine)