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Quick Tyrosine Summary Points

  • Tyrosine is an amino acid, which is a prescursor to a number of bioactive compounds in our body
  • Tyrosine can be found in foods such as fish, dairy and poultry and straight tyrosine supplementation results in higher levels than if you were to ingest the same amount in a protein
  • Tyrosine is considered an 'anti-stress' ingredient and helps to reduce the negative effects of physical, temperature and other types of stress.
  • It is also a precursor to thyroid hormone, which can support metabolism.
  • Doses vary, but are usually between 500mg-2000mg.
  • Tyrosine supplementation is generally safe and stacks easily with most supplements including protein, pre workouts, creatine and fat burners.

What is Tyrosine?

Tyrosine is a conditionally essential amino acid because under normal conditions the body synthesizes sufficient quantities from phenylalanine. Tyrosine is classified as a large neutral amino acid (LNAA) because of its chemical structure and properties. For those with phenylketonuria, (a condition which prevents conversion of phenylalanine to tyrosine); tyrosine is an essential amino acid. Tyrosine is incorporated into proteins of all life forms and is a precursor for synthesis of a number of important bioactive substances within the body.

Tyrosine in the Body and Food

In the body, tyrosine serves as a precursor for the synthesis of thyroxin, melanin, and the neurotransmitters dopamine and norepinephrine1. Thyroxin is the body’s main thyroid hormone, whereas melanin is the pigment responsible for skin and hair colour that provides protection against harmful ultraviolet rays. Food sources of tyrosine include fish, soy products, poultry, eggs, dairy products, lima beans, almonds, peanuts, sesame seeds, pumpkin seeds, wheat germ, oats, avocados, and bananas1.

To get into the brain, tyrosine is transported from the blood using a carrier system that is shared by other LNAA, which include: tryptophan; valine; isoleucine; leucine; and phenylalanine. Therefore, the relative concentration of these amino acids affects how much tyrosine is transported into the brain for catecholamine synthesis. For this reason, studies have shown that ingesting pure tyrosine on its own results in a larger rise in plasma tyrosine compared to ingesting tyrosine as part of a protein.

Functions of Tyrosine

Once ingested and absorbed, tyrosine is either: (1) absorbed into the tissues and incorporated into proteins and peptides; (2) used as precursors in smaller amounts for thyroxin, melanin, and neurotransmitter synthesis; or (3) metabolised to glucose to be used for energy production1. The catecholamines are involved in basic nervous system activities such as movement, memory, attention, problem solving, desire, motivation, “fight or flight” response, heart rate and stroke volume. Clinical conditions for which tyrosine supplementation may be of therapeutic benefit include depression, hypertension, stress, cognitive function and memory, Parkinson's disease, phenylketonuria, and narcolepsy1.

Tyrosine Supplements

Tyrosine is the precursor of the catecholamines and alterations in the availability of tyrosine to the brain have been shown to influence the synthesis of both dopamine and norepinephrine in animals and humans2. This is the reason that tyrosine is included in a number of pre-workout products as a means of enhancing dopamine/norepinephrine and the associated mental drive and focus. However, in keeping with the fact that tyrosine has to compete with other LNAA to cross the blood brain barrier to affect dopamine and norepinephrine, it’s important that tyrosine is taken on its own and not as part of a protein supplement or with other LNAA such as isoleucine, leucine, valine or tryptophan2.

Benefits of Tyrosine

Because of its role in catecholamine production, tyrosine is also often touted as a great ‘anti-stress’ supplement. However, the few studies that have explored this effect of tyrosine supplementation seem to indicate that rather than reduce stress, tyrosine supplementation can prevent a decline in cognitive function in response to specific types of physical stress. These physical stressors include those typically experienced by members of the army or military3. Examples include cold stress, the combination of cold stress and high-altitude stress, extended wakefulness and lower body negative pressure stress (such as occurs during space flight).

Tyrosine and Thyroid

Because tyrosine serves as the precursor to thyroid hormone, it is sometimes found in fat loss products which are designed to work by increasing the body’s metabolic rate, which is one of thyroid hormones main functions.

Tyrosine Dosage

Many of the studies examining the effectiveness of tyrosine supplementation in defence personnel, depression, parkinson’s disease, attention deficit disorder and narcolepsy have used between 50 and 150 mg/kg bodyweight, which equates to between 3.5g and 10.5g for a 70kg individual1. Such doses are only achieved by taking pure tyrosine powder or capsules. It is not possible to reach such doses from using pre-workout and fat loss supplements that contain tyrosine.

Tyrosine Side Effects

Tyrosine supplementation is generally safe with infrequent reports of side effects1. Occasional nausea, diarrhea, headaches, vomiting, or insomnia are reported by those taking higher doses of tyrosine (>150 mg/kg daily)1. Because tyrosine may enhance dopamine levels, it is advised that supplements containing high levels of tyrosine only be taken in the morning, so as to avoid any possible negative impact of sleep. However, it’s very hard to reach these levels unless you are taking pure tyrosine powder. Tyrosine supplementation safety studies in pregnancy have not been conducted. Therefore, patients who are pregnant or wish to become pregnant should consult a health care practitioner regarding tyrosine supplementation.

References
1. L-tyrosine. Monograph. Alternative Medicine Review. 2007;12(4):364-368.
2. Melamed E, et al. Plasma tyrosine in normal humans: effects of oral tyrosine and protein-containing meals. Journal of Neural Transmission. 1980;47(4):299-306.
3. Young SN. L-tyrosine to alleviate the effects of stress? Journal of Psychiatry & Neuroscience. 2007;32(3):224.

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