How Tyrosine, an Amino Acid, Works in the Body

L-tyrosine (also referred to as tyrosine) is an amino acid. It is considered a nonessential amino acid since the body can make tyrosine from another amino acid, phenylalanine.

Tyrosine has several functions in the body, including:

• It is one of several amino acids, the building blocks of proteins. It is involved in the structure of almost all proteins in the body.
• It is a precursor to the neurotransmitters epinephrine, norepinephrine, and dopamine.
• It helps to produce melanin, the pigment responsible for hair and skin color.
• It helps the adrenal, pituitary, and thyroid glands produce hormones.

Tyrosine is found in many foods we eat, like eggs, chicken, turkey, fish, soy, cheese, yogurt, and some nuts and seeds. It is also available in supplement form.

This article reviews everything you should know about tyrosine supplementation.

Uses of L-Tyrosine

Supplement use should be individualized and vetted by a healthcare professional, such as a registered dietitian, pharmacist, or healthcare provider. No supplement is intended to treat, cure, or prevent disease.

Tyrosine is made in the body from another amino acid called phenylalanine. It is used in the body to make the catecholamines dopamine and norepinephrine. Under stressful conditions, these catecholamines can be depleted.

Tyrosine is marketed for stress relief, brain health, and improved cognitive function. It is also thought to stimulate thyroid hormone production in people with hypothyroidism (low thyroid function), including those with Hashimoto thyroiditis (the autoimmune form of hypothyroidism).

To date, there is very little evidence to support any of these claims, and most of the evidence involves small studies with variable results.

Improved Cognitive Function During Physical Stress

Tyrosine is often marketed to alleviate the effects of stress. The definition of stress is left open to interpretation, but the research supporting tyrosine evaluated its effects during periods of extreme physical stress.

During periods of physical stress, the body releases more catecholamines, resulting in a depletion of their levels.

Studies have evaluated anywhere from 2 grams (g) to 20 g of tyrosine on cognitive performance during periods of prolonged sleep deprivation, exposure to extremely cold temperatures, or during demanding military combat training.

In another study, tyrosine supplementation improved cognitive functioning, such as response inhibition, task switching, and working memory in young adults. However, this was mostly seen in short-term stressful situations or cognitively demanding scenarios.

These studies show improved cognitive function with tyrosine supplementation during extreme physical stress. Therefore, these results don't necessarily apply to the general population, who may experience mild stress from psychosocial factors or daily activities.

Additionally, taking tyrosine will not help you feel less stressed, which some may mistakenly interpret from the marketing claims.

Phenylketonuria (PKU)

Phenylketonuria (PKU) is an inherited disorder in which the person cannot process phenylalanine appropriately.

Since phenylalanine converts to tyrosine, this could lead to low levels of tyrosine in the body. People with PKU may be advised to consume a diet containing tyrosine and very little phenylalanine to prevent low tyrosine levels.

Research that evaluated tyrosine supplementation in people with PKU found that tyrosine levels in the blood were higher with supplementation. However, there was no difference between the supplement or placebo group in any of the other outcomes measured.

What Are the Side Effects of L-Tyrosine?

Tyrosine is generally recognized as safe (GRAS) by the FDA. As a supplement, tyrosine is mostly safe, although long-term safety and safety in high doses are not known. Studies have used doses of 150 milligrams (mg) per kilogram of body weight (mg/kg) without harmful effects.

Some have reported nausea, fatigue, and headaches with tyrosine supplementation.

Precautions

There is insufficient data on the safety of supplementing tyrosine in pregnant or breastfeeding people. Therefore, sticking to amounts of tyrosine found naturally in foods is safest.

People with hyperthyroidism (overactive thyroid gland) should avoid tyrosine supplements as they can increase thyroid hormone production and worsen symptoms of hyperthyroidism (including Graves' disease, the autoimmune form of hyperthyroidism).

Tyrosine can also trigger migraine headaches. If you have frequent migraines, avoid tyrosine supplementation.

Dosage: How Much L-Tyrosine Should I Take?

Tyrosine is available in the foods that we eat. Therefore, most people get enough tyrosine from their diet alone.

For adults, the estimated amino acid requirement for phenylalanine and tyrosine combined is 14 mg/kg body weight daily.

Dosage may vary depending on what you're taking it for. Talk to a healthcare provider or a registered dietitian nutritionist on the most appropriate dosing regimen for you

There is not a lot of data on the effects of high doses of tyrosine or toxicity. The possible ill effects of such high doses over the long term are not known.

Interactions

Some medications may interact with supplemental tyrosine:

• Levodopa is a medication used for Parkinson's disease. Levodopa and tyrosine can compete for absorption in the small intestine, which could influence how well they work. This can be avoided by dosing tyrosine two hours apart from the levodopa dose. Additionally, high protein intake, in general, may make levodopa less effective. But the benefit of improved efficacy of levodopa should be weighed against the risk of tyrosine deficiency by you and your healthcare provider.
• Monoamine oxidase inhibitors (MAOIs) combined with high-tyramine foods can increase blood pressure to dangerous levels. Tyrosine is broken down to tyramine. In theory, it could affect blood pressure. But it is not yet known if supplementing tyrosine would increase tyramine levels. For now, it is best to avoid tyrosine supplements while prescribed MAOIs and discuss your supplementation needs with your healthcare provider.
• Thyroid medications are used to control levels of thyroid hormones. Supplementing tyrosine may also influence hormone levels and raise levels too high.

It is essential to carefully read the ingredients list and nutrition facts panel of a supplement to know which ingredients and how much of each ingredient is included. Review the supplement label with your healthcare provider to discuss any potential interactions with foods, other supplements, and medications. 

How to Store L-Tyrosine

Store tyrosine as you would for other supplements, following the manufacturer's guidelines for the best shelf life. Always store supplements and medications out of the reach of children and pets to prevent accidental consumption.

Sources of L-Tyrosine & What To Look For

Tyrosine is easy to get through diet alone. High tyrosine foods include:

• Meat, such as chicken or turkey
• Fish
• Dairy products, like cheese, or yogurt
• Eggs
• Soy
• Avocado
• Wheats and oats
• Pumpkin seeds
• Peanuts

Tyrosine supplementation can be found in its free form. It can also be found as N-acetyl L-Tyrosine (NALT). The conversion rate of NALT to tyrosine is lower so some may take higher doses of NALT.

Tyrosine is available as a combination product, with high amounts of several B vitamins. It can also be found combined with iodine. Products are often marketed and labeled for "brain health," "neurotransmitter support during stress," or "thyroid support." As mentioned previously, there is little evidence to support these claims.

When looking for supplements, be sure to find ones that have been third-party tested so that you can trust they contain what the label claims and are free of harmful contaminants.

Summary

Tyrosine is a nonessential amino acid that is produced in the body. It is also easily available in many of the foods we eat. For this reason, a food-first approach to getting more tyrosine is usually preferred.

Tyrosine is marketed to relieve stress, ease symptoms of hypothyroidism, and improve brain health, but there is very little scientific evidence to support any of these claims. Speak with a healthcare provider if you are interested in using supplements of any sort.