8 Potential L-Tyrosine Benefits + Dosage & Side Effects

8 Potential L-Tyrosine Benefits + Dosage & Side Effects

8 Potential L-Tyrosine Benefits + Dosage & Side Effects

People use L-tyrosine to boost cognition, mood, and thyroid hormones, especially when they’re under stress. However, research says it may do the opposite and worsen mental health in some cases. Read on to discover both sides of L-tyrosine supplements and learn what the evidence suggests.

The “Cheese” Amino Acid

L-tyrosine is a naturally occurring form of tyrosine, an amino acid the body uses to make proteins, neurotransmitters, and other vital compounds [1].

We don’t depend on food sources of tyrosine since we can make it from another amino acid, phenylalanine; this makes tyrosine a non-essential amino acid. Still, you can ensure its optimal levels by eating a variety of tyrosine-rich foods such as [2, 3]:

  • Cheese and dairy
  • Turkey
  • Beans
  • Eggs
  • Chicken
  • Peanuts

Did you know? Scientists named tyrosine after cheese (Greek: tyros), where they discovered it.

L-tyrosine is a popular nootropic supplement; people use it to boost cognition and alertness under stress. It’s used alone or combined with other ingredients in protein and pre-workout supplements.

However, l-tyrosine supplements have not been approved by the FDA for medical use. Supplements generally lack solid clinical research. Regulations set manufacturing standards for them but don’t guarantee that they’re safe or effective. Speak with your doctor before supplementing.


  • May boost cognition and alertness under stress
  • May improve mood
  • May increase thyroid hormones
  • May help with fibromyalgia


  • May cause headache and anxiety
  • May worsen cognition in the elderly
  • Interacts with L-DOPA and thyroid medications
  • May not help with depression and attention disorders
  • May not improve physical performance
  • Long-term safety unknown

Roles and Functions

Source: https://commons.wikimedia.org/wiki/File:Conversion_of_phenylalanine_and_tyrosine_to_its_biologically_important_derivatives.png

In the body, tyrosine acts as a precursor to neurotransmitters called catecholamines [4]:

  • Dopamine
  • Norepinephrine (noradrenaline)
  • Epinephrine (adrenaline)

These components play central roles in mental health, cognition, behavior, and stress response. They also control blood pressure and metabolism [5, 6].

People use L-tyrosine under stressful conditions that are more ly to deplete catecholamines.

Tyrosine helps build thyroid hormones and the skin pigment melanin [7, 8].

N-Acetyl-L-Tyrosine (NALT)

N-acetyl-L-tyrosine (NALT or NAT) is more water-soluble than L-tyrosine and thus more suitable for intravenous nutrition for people who can’t eat and drink [9].

As a nutritional supplement, our bodies supposedly use it better than L-tyrosine, but the evidence tells a different story. We metabolize only 25% of NALT into free tyrosine and eliminate 35-38% with the urine [9, 10, 11].

In a study of 13 subjects, N-acetyl-L-tyrosine didnt increase tyrosine levels at all [12].

Thus, L-tyrosine remains a better option for oral supplementation.

Learn more about N-acetyl-L-tyrosine.

1) Phenylketonuria

People with an inborn metabolic disorder – phenylketonuria (PKU) – are unable to break down phenylalanine properly. In turn, the buildup of phenylalanine causes brain damage and cognitive impairment [13, 14, 15].

Tyrosine is a component of medical foods for people with phenylketonuria.

These patients should follow a special low-protein diet to minimize the intake of phenylalanine. Additionally, they should add tyrosine as a component of medical food. This reduces the risk of tyrosine deficiency since the body converts phenylalanine into tyrosine.

On the other hand, L-tyrosine supplementation for PKU may sound reasonable, but a Cochrane Database review of six clinical trials failed to confirm its benefits [16].

To avoid variations in blood tyrosine levels, doctors suggest using protein substitutes with optimized tyrosine content (3-6g/100g) instead [17, 18, 19, 20].

2) Cognitive Performance and Alertness (from Stress or Sleep Deprivation)

A review of 15 clinical trials investigated the effects of L-tyrosine loading – short bouts of higher doses – on cognition and behavior. This dosing pattern prevented catecholamine depletion and boosted mental function in stressful and demanding situations [21].

It showed the best results in people exposed to:

  • Multitasking and distractions [22, 23, 24]
  • Sleep deprivation [25, 26]
  • Harsh military training [27, 28]
  • Cold weather [29, 30, 31]

Some people use L-tyrosine to enhance their physical performance under stress. However, multiple reviews failed to confirm this effect [21, 32, 33, 34].

Additionally, L-tyrosine may not improve cognitive performance under normal conditions. In older adults, L-tyrosine loading even produced the opposite effects – worsening memory and cognitive function [35].

Insufficient Evidence:

No valid clinical evidence supports the use of L-tyrosine for any of the conditions in this section. Below is a summary of up-to-date animal studies, cell-based research, or low-quality clinical trials which should spark further investigation. However, you shouldn’t interpret them as supportive of any health benefit.

3) Thyroid Hormones Balance

With the help of selenium, the body combines tyrosine and iodine to make thyroid hormones [7].

In 85 volunteers, supplementation with high doses of L-tyrosine (12 g daily) during harsh winter slightly increased T3, the active thyroid hormone. It also greatly reduced TSH, high levels of which are linked with hypothyroidism and stress [36].

Tyrosine supplementation prevented thyroid hormone drops in mice exposed to chronic stress [37].

4) Narcolepsy

Patients with narcolepsy struggle to stay awake during the day. They often experience cataplexy (sudden muscle weakness with intact awareness) and sleep paralysis [38].

L-tyrosine supplies dopamine and noradrenaline, neurotransmitters that promote arousal and prevent cataplexy [39, 4].

In a study of 10 patients, L-tyrosine improved only three of more than 20 tested symptoms. The patients felt less tired and more alert [40].

A group of doctors managed to handle daytime sleep attacks and cataplexy with L-tyrosine in eight patients. They kept using this approach in other narcolepsy patients after the initial success. This study was limited by its open-label design, small sample, and a lack of placebo controls. It doesn’t allow for a definite conclusion [41].

5) Addiction and Substance Withdrawal

Dopamine plays a central role in the brain’s reward pathway. Scientists first thought that it makes certain things (such as food and sex) enjoyable. New research suggests dopamine actually doesn’t make us feel pleasure, it makes us want it. People with addiction may be depleting or over-sensitizing this pathway, which increases their cravings and drug-seeking behavior [42].

In 83 former heroin addicts, a combination of L-tyrosine and other neurotransmitter precursors (lecithin, L-glutamine, and 5-HTP) significantly improved withdrawal symptoms such as [43]:

  • Anxiety
  • Depression
  • Anger and hostility
  • Fatigue
  • Suppressed vigor

6) Weight Loss

Many supplements are promoted to stimulate weight loss, but none of them has yet been supported by strong clinical evidence and approved by the health authorities. A healthy, calorie-controlled diet and increased physical activity remain the only proven strategies for weight control [44].

Tyrosine supplies catecholamines and thyroid hormones, which both enhance metabolism and energy production. For this reason, many people want to know if L-tyrosine can boost weight loss.

A supplement containing L-tyrosine, green tea extract, and caffeine slightly enhanced weight loss in 80 obese adults. Other ingredients have ly contributed to the results [45].

No other trials have documented the benefits of L-tyrosine for weight loss.

7) Attention Disorders

In a clinical trial, L-tyrosine improved attention in eight of 12 participants with attention deficit disorder over two weeks. However, after six weeks, all patients developed a tolerance to the treatment, and their improvement stalled [46].

L-tyrosine supplementation provided no benefits to 7 children with ADHD [47].

Impaired production of dopamine and noradrenaline may trigger attention disorders, and such cases may be more ly to benefit from tyrosine supplementation [48].

Combination With Adderall

Adderall is an amphetamine-based drug for attention disorders; its long-term use may deplete brain catecholamines [49, 50].

L-tyrosine helps restore catecholamines, and some people combine it with Adderall to “lessen the side effects.” However, this combination should be avoided. No studies have verified its safety and efficacy and potentially dangerous interactions are possible.

According to the available research, L-tyrosine may not help with depression and physical performance, too [21, 32, 33, 34, 51].

8) Mood Improvement

Evidence is lacking to support the use of L-tyrosine in people with depression and mood disorders, but L-tyrosine from dietary sources may contribute to mental health.

According to some scientists, imbalances in brain neurotransmitters play a role in depression and other mood disorders. Since tyrosine enables the production of dopamine and noradrenaline, it may act as nutritional mood support [52].

Limited evidence suggests it may be beneficial for particular mood disorders such as:

  • Depression due to low dopamine [53]
  • Low mood from living in harsh, cold environments [54, 36]
  • Depression after childbirth [55]

However, the above results stem from small clinical trials, some of which lacked placebo controls. A larger trial of 65 patients failed to verify the antidepressant effects of L-tyrosine [51].

It induced no changes in mood or behavior in healthy people under normal conditions [56, 57].

Side Effects

This list does not cover all possible side effects. Contact your doctor or pharmacist if you notice any other side effects. In the US, you may report side effects to the FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch

Source: https://selfhacked.com/blog/tyrosine-6-proven-health-benefits-tyrosine/

What You Need to Know About L-theanine

8 Potential L-Tyrosine Benefits + Dosage & Side Effects

I often encourage my patients to drink tea. Black tea is a lower-caffeine alternative to coffee during the day, and decaffeinated tea can be a calming part of a nighttime power-down ritual before bed. Whatever time of day or night, drinking a cup of tea can be a soothing, relaxing ritual. I often drink tea myself—my favorite is my personal recipe for banana tea.

In addition to its calming qualities, tea also contains compounds that deliver some real health benefits. One of those compounds: L-theanine.

Fortunately, you can also get L-theanine in supplement form, which can help with relaxation, focus, and sleep. Let’s take a closer look at L-theanine and its calming, centering, sleep-boosting abilities.

What is L-theanine?

L-theanine is an amino acid that is found in tea leaves. It was identified in tea by Japanese scientists in 1949. While tea is the most common dietary source for L-theanine, this compound is also found in some types of mushrooms. In foods, particularly green tea, L-theanine is thought to be a source of umami, the savory, brothy taste.

Scientists studying umami flavor have made some interesting discoveries. Umami has been linked to decreased risk for obesity. It may stimulate metabolism, and may boost sensations of fullness and lengthen the time before hunger returns after eating.

There’s also evidence suggesting that L-theanine, when consumed in tea, may change taste perception, specifically diminishing the taste of bitterness in foods such as chocolate and grapefruit.

How L-theanine Works

L-theanine promotes relaxation and facilitates sleep by contributing to a number of changes in the brain:

  • Boosts levels of GABA and other calming brain chemicals. L-theanine elevates levels of GABA, as well as serotonin and dopamine. These chemicals are known as neurotransmitters, and they work in the brain to regulate emotions, mood, concentration, alertness, and sleep, as well as appetite, energy, and other cognitive skills. Increasing levels of these calming brain chemicals promotes relaxation and can help with sleep.
  • Lowers levels of “excitatory” brain chemicals. At the same time it is increasing chemicals that promote feelings of calm, L-theanine also reduces levels of chemicals in the brain that are linked to stress and anxiety. This may also be a way that L-theanine can protect brain cells against stress and age-related damage.
  • Enhances alpha brain waves. Alpha brain waves are associated with a state of “wakeful relaxation.” That’s the state of mind you experience when meditating, being creative, or letting your mind wander in daydreaming. Alpha waves are also present during REM sleep. L-theanine appears to trigger the release of alpha-waves, which enhances relaxation, focus, and creativity. One of the appealing aspects of L-theanine is that it works to relax without sedating. That can make L-theanine a good choice for people who are looking to enhance their “wakeful relaxation,” without worrying about becoming sleepy and fatigued during the day.

Benefits of L-theanine

Improving sleep. With its ability to increase relaxation and lower stress, L-theanine can help in sleep in a number of ways.

L-theanine may help people fall asleep more quickly and easily at bedtime, thanks to the relaxation boost it delivers.

Research also shows L-theanine can improve the quality of sleep—not by acting as a sedative, but by lowering anxiety and promoting relaxation.

There’s evidence that L-theanine may help improve sleep quality in children with attention deficit hyperactivity disorder (ADHD). A study examined the effects on the sleep of boys ages 8-12, and found that the supplement worked safely and effectively to improve the quality of their sleep, helping them to sleep more soundly.

Reducing stress and anxiety. L-theanine is what’s known as an anxiolytic—it works to reduce anxiety. Some anxiolytics, such as valerian and hops, have sedative effects. L-theanine, on the other hand, promotes relaxation and stress reduction without sedating. L-theanine can help foster a state of calm, attentive wakefulness.

L-theanine has positive effects on both the mental and physical symptoms of stress, including lowering heart rate and blood pressure.

Research suggests that L-theanine can help reduce anxiety in people with schizophrenia and schizoaffective disorder.

Enhancing attention, focus, memory and learning. Under stress, the body increases production of certain hormones, including cortisol and corticosterone. These hormone changes inhibit some brain activity, including memory formation and spatial learning. L-theanine helps to lower levels of the stress hormone corticosterone, and avoid the interference with memory and learning.

L-theanine may help boost other cognitive skills. Research shows L-theanine can increase attention span and reaction time in people who are prone to anxiety. It may help improve accuracy—one study shows that taking L-theanine reduced the number of errors made in a test of attention.

Sometimes, L-theanine is used with caffeine to enhance cognitive skills. Studies show that combinations of L-theanine and caffeine can improve attention span, enhance the ability to process visual information, and increase accuracy when switching from one task to another.

Helping maintain a healthy weight. The anti-anxiety and sleep-promoting abilities of L-theanine may help people to maintain a healthy weight. After all, getting enough sleep and limiting stress are both key to sticking with a healthy diet and avoiding weight gain.

L-theanine may also play a more direct role in weight maintenance. There’s scientific evidence indicating L-theanine may help to limit fat accumulation and weight gain, and pay help to protect against obesity.

What to Know

Always consult your doctor before you begin taking a supplement or make any changes to your existing medication and supplement routine. This is not medical advice, but it is information you can use as a conversation-starter with your physician at your next appointment.


The following doses are amounts that have been investigated in scientific studies. In general, it is recommended that users begin with the smallest suggested dose, and gradually increase until it has an effect.

  • For sleep, stress and other uses: 100 mg to 400 mg
  • In combination with caffeine: 12-100 mg L-theanine, 30-100 mg caffeine

Possible Side Effects

L-theanine is generally well tolerated by healthy adults.

People in these groups should consult with a physician before using an L-theanine supplement:

  • Pregnant women and those who are breastfeeding.
  • Individuals with low blood pressure. L-theanine may lower blood pressure. If you have low blood pressure, speak with your doctor before beginning to use L-theanine.
  • Children. Consult your child’s physician before beginning their use of L-theanine.


The following medications and other supplements may interact with L-theanine.

Effects may include increasing or decreasing sleepiness and drowsiness, interfering with the effectiveness of the medications or supplements, and interfering with the condition that is being treated by the medication or supplement.

These are lists of commonly used medications and supplements that have scientifically identified interactions with L-theanine. People who take these or any other medications and supplements should consult with a physician before beginning to use L-theanine.

Interactions with medications

  • Medications used to treat high blood pressure
  • Stimulant medications

Interactions with other supplements

Supplements that contain caffeine. L-theanine may interrupt the stimulating effects of caffeine and herbs or supplements that contain caffeine. Some of these include:

  • Coffee
  • Black tea
  • Oolong tea
  • Guarana
  • Mate
  • Cola

Supplements that lower blood pressure. L-theanine may lower blood pressure, and combining this supplement with other blood-pressure lowering supplements may cause blood pressure to drop too much. Some of these include:

  • Andographis
  • Casein peptides
  • Cat’s claw
  • Coenzyme Q-10
  • Fish oil
  • L-arginine
  • Lycium
  • Stinging nettle

People have relied on the stress-relieving, sleep-promoting powers of L-theanine for centuries, by drinking tea—especially green tea. You don’t have to be a tea drinker to benefit from the soothing properties of this ancient herb—and even if you already enjoy a regular cup of tea, you may find an L-theanine supplement helps with relaxation, stress, and sleep.

Sweet Dreams,

Michael J. Breus, PhDThe Sleep Doctor™


Source: https://www.psychologytoday.com/us/blog/sleep-newzzz/201708/what-you-need-know-about-l-theanine

Tyrosine Uses, Benefits & Dosage – Drugs.com Herbal Database

8 Potential L-Tyrosine Benefits + Dosage & Side Effects

Medically reviewed by Drugs.com. Last updated on Dec 31, 2019.

Scientific Name(s): 4-hydroxyphenylalanine, C9H11NO3
Common Name(s): L-tyrosine, Tyrosine


There is no evidence to support the use of tyrosine in the metabolic genetic disorder phenylketonuria. Some evidence for improved cognitive performance in conditions of stress, including sleep deprivation, exists. Clinical trial data for other conditions is limited and does not support tyrosine supplementation, including for the enhancement of sports performance.


Limited clinical studies use 100 to 150 mg/kg per day. Manufacturers commonly recommend 500 to 1,500 mg/day, and dosages of more than 12 g/day are not recommended.


Tyrosine is contraindicated in hyperthyroidism or Graves disease because it may increase levels of thyroid hormone. Coadministration of tyrosine with monoamine oxidase inhibitors (MAOIs) is contraindicated.


Information regarding safety and efficacy in pregnancy and lactation is lacking.


Coadministration of tyrosine and MAOIs is contraindicated. Tyrosine could increase levels of thyroid hormone and levodopa.

Adverse Reactions

Information is limited. Tyrosine supplementation may trigger migraine.


Tyrosine is made endogenously from phenylalanine and can be found in soy products, milk, cheese, yogurt, chicken, turkey, fish, peanuts, almonds, bananas, lima beans, avocado, pumpkin seeds, and sesame seeds.Zimmermann 2001


The name tyrosine is derived from the Greek tyri, meaning “cheese.” Tyrosine was first identified in cheese protein casein in 1846 by German chemist Justus von Liebig.


Tyrosine is a nonessential, yet indispensable, amino acid made endogenously and eaten in a usual diet. It is a fundamental building block for proteins, specifically for neurotransmitters. Tyrosine is converted to L-dopa, dopamine, epinephrine, norepinephrine, triiodothyronine (T3), thyroxine (T4), and melanin.

Uses and Pharmacology

Research reveals no recent animal data regarding the use of supplemental tyrosine for use in depression.

Despite a theoretical basis for the use of tyrosine in depression, studies conducted in the 1980s using small sample sizes did not show any benefit.Meyers 2000, Parker 2011 More recent studies focused on serotonin precursors, revealing little evidence of a place in therapy for tyrosine.Meyers 2000, Parker 2011, Fernstrom 2000

Research reveals no recent animal data regarding the use of supplemental tyrosine for the use of performance enhancement.

Limited clinical studies provide equivocal data on the effects of supplemental tyrosine in exercise,Chinevere 2002, Tumilty 2011 with older studies conducted in the 1980s reporting more positive findings.

Among 8 cyclists exercising in heat, tyrosine 150 mg/kg appeared to improve endurance,Tumilty 2011 while a similar trial also conducted among cyclists resulted in increased plasma tyrosine levels but not improved performance; however, tyrosine may have altered their perception of fatigue.Chinevere 2002

The effect of tyrosine on core cognitive-control performance, as measured by stopping overt responses, was investigated in a small double-blind, randomized, placebo-controlled cross-over study in 22 young healthy female adults. One hour after administration of L-tyrosine 2 g (in 400 mL orange juice), participants were observed to more efficiently inhibit unwanted actions compared to the placebo phase (P

Source: https://www.drugs.com/npp/tyrosine.html

L-Tyrosine (tyrosine) Uses, Side Effects, Dosage & Interactions

8 Potential L-Tyrosine Benefits + Dosage & Side Effects

Tyrosine is an amino acid, which is a building block of protein that occurs naturally in the body. Tyrosine can also be found in certain foods such as meat, fish, eggs, dairy products, beans, nuts, oats, and wheat.

Some people have low levels of tyrosine in their bodies because of a hereditary condition called phenylketonuria (PKU). In people with PKU, the body cannot process an amino acid called phenylalanine, which the body needs to produce tyrosine.

Tyrosine is given as a supplement to increase tyrosine levels in people with PKU.

Tyrosine has been used in alternative medicine as a possibly effective aid in improving mental performance, alertness, or memory.

Tyrosine has also been used to treat depression or attention deficit disorder (ADD or ADHD). However, research has shown that tyrosine may not be effective in treating these conditions. Tyrosine also may not be be effective in improving exercise performance.

Other uses not proven with research have included dementia, high blood pressure, narcolepsy, schizophrenia, weight loss, premenstrual syndrome, Parkinson's disease, chronic fatigue syndrome, alcoholism, cocaine addiction, and other conditions.

It is not certain whether tyrosine is effective in treating any medical condition. Medicinal use of this product has not been approved by the FDA. Tyrosine should not be used in place of medication prescribed for you by your doctor.

Tyrosine is often sold as an herbal supplement. There are no regulated manufacturing standards in place for many herbal compounds and some marketed supplements have been found to be contaminated with toxic metals or other drugs. Herbal/health supplements should be purchased from a reliable source to minimize the risk of contamination.

Tyrosine may also be used for purposes not listed in this product guide.

What are the possible side effects of tyrosine (L-Tyrosine)?

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Although not all side effects are known, tyrosine is thought to be ly safe in most adults when taken for up to 3 months.

Common side effects may include:

  • nausea, heartburn;
  • headache;
  • joint pain; or
  • feeling tired.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What is the most important information I should know about tyrosine (L-Tyrosine)?

Follow all directions on the product label and package. Tell each of your healthcare providers about all your medical conditions, allergies, and all medicines you use.

What should I discuss with my healthcare provider before taking tyrosine (L-Tyrosine)?

Before using tyrosine, talk to your healthcare provider. You may not be able to use tyrosine if you have certain medical conditions, especially:

  • overactive thyroid; or
  • Graves disease.

It is not known whether tyrosine will harm an unborn baby. Do not use this product without medical advice if you are pregnant.

It is not known whether tyrosine passes into breast milk or if it could harm a nursing baby. Do not use this product without medical advice if you are breast-feeding a baby.

Do not give any herbal/health supplement to a child without medical advice.

How should I take tyrosine (L-Tyrosine)?

When considering the use of herbal supplements, seek the advice of your doctor. You may also consider consulting a practitioner who is trained in the use of herbal/health supplements.

If you choose to use tyrosine, use it as directed on the package or as directed by your doctor, pharmacist, or other healthcare provider. Do not use more of this product than is recommended on the label.

Your dose of tyrosine will depend on the amount of protein you consume in your diet. Follow your doctor's dosing instructions very carefully.

Tyrosine is only part of a complete program of treatment that may also include a special diet. Follow the diet plan created for you by your doctor or nutrition counselor. Get familiar with the list of foods you must eat or avoid to help control your condition.

Call your doctor if the condition you are treating with tyrosine does not improve, or if it gets worse while using this product.

Store at room temperature away from moisture and heat.

Vitamin D Deficiency: How Much Vitamin D Is Enough? See Slideshow

What happens if I miss a dose (L-Tyrosine)?

Skip the missed dose if it is almost time for your next scheduled dose. Do not use extra tyrosine to make up the missed dose.

What happens if I overdose (L-Tyrosine)?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

What should I avoid while taking tyrosine (L-Tyrosine)?

Follow your healthcare provider's instructions about any restrictions on food, beverages, or activity.

What other drugs will affect tyrosine (L-Tyrosine)?

Do not take tyrosine without medical advice if you are using any of the following medications:

  • levodopa; or
  • thyroid replacement (Synthroid, Levothroid, and others).

This list is not complete. Other drugs may interact with tyrosine, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible interactions are listed in this product guide.

Where can I get more information (L-Tyrosine)?

Consult with a licensed healthcare professional before using any herbal/health supplement. Whether you are treated by a medical doctor or a practitioner trained in the use of natural medicines/supplements, make sure all your healthcare providers know about all of your medical conditions and treatments.

Remember, keep this and all other medicines the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

Every effort has been made to ensure that the information provided by Cerner Multum, Inc. ('Multum') is accurate, up-to-date, and complete, but no guarantee is made to that effect. Drug information contained herein may be time sensitive.

Multum information has been compiled for use by healthcare practitioners and consumers in the United States and therefore Multum does not warrant that uses outside of the United States are appropriate, unless specifically indicated otherwise. Multum's drug information does not endorse drugs, diagnose patients or recommend therapy.

Multum's drug information is an informational resource designed to assist licensed healthcare practitioners in caring for their patients and/or to serve consumers viewing this service as a supplement to, and not a substitute for, the expertise, skill, knowledge and judgment of healthcare practitioners.

The absence of a warning for a given drug or drug combination in no way should be construed to indicate that the drug or drug combination is safe, effective or appropriate for any given patient. Multum does not assume any responsibility for any aspect of healthcare administered with the aid of information Multum provides.

The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the drugs you are taking, check with your doctor, nurse or pharmacist.

Copyright 1996-2019 Cerner Multum, Inc.

Source: https://www.emedicinehealth.com/drug-tyrosine/article_em.htm

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8 Potential L-Tyrosine Benefits + Dosage & Side Effects

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L-tyrosine supplementation does not ameliorate skeletal muscle dysfunction in zebrafish and mouse models of dominant skeletal muscle α-actin nemaline myopathy

8 Potential L-Tyrosine Benefits + Dosage & Side Effects

L-tyrosine supplementation may provide benefit to nemaline myopathy (NM) patients, however previous studies are inconclusive, with no elevation of L-tyrosine levels in blood or tissue reported.

We evaluated the ability of L-tyrosine treatments to improve skeletal muscle function in all three published animal models of NM caused by dominant skeletal muscle α-actin (ACTA1) mutations. Highest safe L-tyrosine concentrations were determined for dosing water and feed of wildtype zebrafish and mice respectively.

NM TgACTA1D286G-eGFP zebrafish treated with 10 μM L-tyrosine from 24 hours to 6 days post fertilization displayed no improvement in swimming distance.

NM TgACTA1D286G mice consuming 2% L-tyrosine supplemented feed from preconception had significant elevations in free L-tyrosine levels in sera (57%) and quadriceps muscle (45%) when examined at 6–7 weeks old. However indicators of skeletal muscle integrity (voluntary exercise, bodyweight, rotarod performance) were not improved.

Additionally no benefit on the mechanical properties, energy metabolism, or atrophy of skeletal muscles of 6–7 month old TgACTA1D286G and KIActa1H40Y mice eventuated from consuming a 2% L-tyrosine supplemented diet for 4 weeks. Therefore this study yields important information on aspects of the clinical utility of L-tyrosine for ACTA1 NM.

Tyrosine is a non-essential amino acid that serves as a precursor for several biologically active substances including the brain catecholamine neurotransmitters norepinephrine (NE) and dopamine.

Tyrosine may be derived from the diet or via the enzymatic action of phenylalanine hydroxylase on phenylalanine present in the liver, leading to the production of L-tyrosine (the biologically active form of tyrosine1). In humans, oral ingestion of L-tyrosine can improve stress-induced cognitive and behavioural deficits1,2.

Additionally, acute L-tyrosine ingestion is thought to enhance performance via improvements to aerobic power, cognitive performance, neurotransmitter synthesis, and stress related exercise3.

L-tyrosine treatment in rodents can reduce deficits in locomotor activity in old mice following cold water stress, alter stress-related changes in aggression in young mice4, and can protect against both neurochemical and behavioural effects induced by various states of stress5,6.

Dietary supplementation with L-tyrosine may have therapeutic application for patients with the skeletal muscle disorder nemaline myopathy (NM)7,8,9. NM is a mainly congenital-onset disorder producing weakened skeletal muscles that contain the characteristic pathological features nemaline bodies10.

However no correlation has been shown to exist between the prevalence of nemaline bodies and the degree of skeletal muscle weakness11,12. Twelve different genes can cause NM13,14,15, with a significant proportion of all NM-causing mutations being within the skeletal muscle α-actin gene, ACTA113.

The majority of patients with ACTA1-NM have a severe phenotype leading to death within the first year of life16.

At present, no curative treatment exists, highlighting the importance to thoroughly test plausible therapies and for potential novel therapeutic approaches to be identified and investigated.

Daily supplementation of L-tyrosine by an adult male and his 7-year-old son (both with NM) resulted in improved body strength (father), decreased pharyngeal secretions (son), and improved general stamina (both)7.

After 10 days of L-tyrosine withdrawal, both patients reported reversion to previous clinical conditions, suggesting the improved conditions resulted from L-tyrosine administration7.

A subsequent small trial contained 5 genetically undefined NM patients (4 infants, 1 adolescent with childhood onset) receiving between 250 to 3000 mg/d of powdered or capsule L-tyrosine for 2 to 5 months9.

Within 72 h on the L-tyrosine regime, all infants displayed initial improvements in “sialorrhoea, skeletal muscle strength and energy levels”9. Additionally, L-tyrosine (250 mg/d) from 3 months of age was reported to produce marked reduction in oral secretions and improvement in skeletal muscle strength in a severely affected NM patient, however the patient died at 4 months with sudden cardiorespiratory failure17.

A murine model of NM due to an Acta1 mutation (KIActa1H40Y) was orally dosed via syringe with L-tyrosine (25 mg/d) for 4 weeks, from 4 weeks of age18.

This study concluded that L-tyrosine supplementation alleviated mobility deficits and skeletal muscle pathologies characteristic of KIActa1H40Y mice.

However, the study did not address modulatory effects of the L-tyrosine dosing on the early lethality of male mice, nor did it report the sera or tissue levels of L-tyrosine.

Due to the limited, albeit promising data from the few patient studies and the single NM mouse model report, we aimed to comprehensively assess one aspect of the reported therapeutic benefit of dietary supplementation of L-tyrosine, skeletal muscle function.

To do so, we chose three dominant NM animal models, each with a missense ACTA1 mutation resulting in an amino acid substitution (a mouse and a zebrafish model with p.D286G; a mouse model with p.H40Y).

In addition to each of these models being suitable animal models of ACTA1-NM, they also have characterised deficits in skeletal muscle function ideal for robust assessment of any improvement due to L-tyrosine.

Initially, we evaluated different levels of L-tyrosine supplementation in wildtype (WT) zebrafish and mice to identify the highest safe L-tyrosine concentration to dose our NM models.

We determined L-tyrosine levels in sera and skeletal muscles of treated mice using this dose, to ensure this supplementation resulted in a significant L-tyrosine increase in the relevant tissues. We tested different L-tyrosine treatment regimes on the dominant ACTA1-NM zebrafish and mouse models, and evaluated potential effects on skeletal muscle function using physiological assays and parameters of voluntary exercise.

A pilot range-finding experiment with WT zebrafish was performed to determine the maximal non-toxic L-tyrosine dose for treatment. Concentrations ranged from 0.1 μM to 10 mM and the survival, heart rate and locomotion of the zebrafish were recorded.

Whilst there was a trend between decreasing concentrations of L-tyrosine and resting heart rate, we observed a significant increase in resting heart rate for zebrafish treated with 0.1 μM and 1 μM, suggesting that L-tyrosine was eliciting a biological effect in the fish.

The experimental dose for L-tyrosine treatment was determined at 10 μM since zebrafish treated with higher concentrations showed significantly reduced survival and swimming performance compared to water treated control fish (Fig. 1).

Figure 1

Toxicity analyses for L-tyrosine treatment of WT zebrafish.

(A) Percentage survival, and (B) resting heart rate in beats per minute (bpm) of zebrafish treated with increasing L-tyrosine concentrations (from 0.1 μM to 10 mM) or H2O (used as a control).

Error bars represent ± s.e.m. for four independent experiments with 30 zebrafish per experiment for survival assays and 10 zebrafish per experiment for heart rate assays, *p 

Source: https://www.nature.com/articles/s41598-018-29437-z?draft=marketing