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L-Tyrosine

L-Tyrosine is an amino acid that is used to produce noradrenaline and dopamine; it appears to reduce stress during exposure to acute stressors (which tend to deplete noradrenaline) and may help to prevent stress-induced memory deficits.

Our evidence-based analysis on l-tyrosine features 50 unique references to scientific papers.

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Summary of L-Tyrosine

Primary information, health benefits, side effects, usage, and other important details

What is L-Tyrosine?

L-Tyrosine is an amino acid found in the diet that is metabolized to produce catecholamines such as dopamine and adrenaline. It is also used in the production of thyroid hormones. For these reasons, weight loss supplements often include it.

What are L-Tyrosine's benefits?

When it comes to the topic of actually increasing dopamine and adrenaline outright, L-tyrosine does not seem to hold much promise. The synthesis of catecholamines is highly regulated in the body, so simply increasing the amount of L-tyrosine in your body does not necessarily increase catecholamine production.

However, some studies have noted that in stressful situations where noradrenaline exerts a protective effect, supplying L-tyrosine seems to provide a 'safety buffer' of building blocks that can prolong the anti-stress effect of catecholamines by delaying their depletion. This has been noted in situations of cold stress and sleep deprivation in humans but at a relatively high dose of 150mg/kg. Improvements in memory during stressful situations have also been found. However, more research is needed to confirm this. What little research we have doesn't suggest an effect on depression.

What are L-Tyrosine'side effects and drawbacks?

It's generally safe, however, studies using high doses have noted increased heart rate, blood pressure, and worsened symptoms of schizophrenia in patients.

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How to Take

Medical Disclaimer

Recommended dosage, active amounts, other details

Anecdotally, L-Tyrosine tends to be taken in doses of 500-2000mg approximately 30-60 minutes before any acute stressor (this tends to be exercise)

Studies in humans showing most anti-stress promise for acute supplemental L-Tyrosine use a dosage range of 100-150mg/kg bodyweight which can be taken 60 minutes before exercise; this is a dosage range of 9-13.5g for a 200lb person and 7-10g for a 150lb person.

If using higher doses and finding digestive issues, this may be split into two doses separated by half an hour (30 and 60 minutes prior to acute stress).

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Human Effect Matrix

The Human Effect Matrix looks at human studies (it excludes animal and in vitro studies) to tell you what effects l-tyrosine has on your body, and how strong these effects are.
Grade Level of Evidence
Robust research conducted with repeated double-blind clinical trials
Multiple studies where at least two are double-blind and placebo controlled
Single double-blind study or multiple cohort studies
Uncontrolled or observational studies only
Level of Evidence
? The amount of high quality evidence. The more evidence, the more we can trust the results.
Outcome Magnitude of effect
? The direction and size of the supplement's impact on each outcome. Some supplements can have an increasing effect, others have a decreasing effect, and others have no effect.
Consistency of research results
? Scientific research does not always agree. HIGH or VERY HIGH means that most of the scientific research agrees.
Notes
grade-b Minor Very High See all 3 studies
Tyrosine appears to effectively improve cognition during acute stressors (altitude and cold being tested most); this appears reliable if the acute stressor is present, but may not be an inherent increase in cognition and it is unsure if it applies to chronic stress and fatigue.
grade-b - High See all 3 studies
It is possible that Tyrosine can reduce blood pressure during stress, but the one study that noted this also noted a reduction in blood pressure in the stressed placebo; other studies have found no influence.
grade-c Minor Very High See 2 studies
Perceptions of stress during acute stressors, as well as related symptoms of acute stress, appear to be reduced following tyrosine ingestion
grade-c Minor Moderate See 2 studies
There appears to be an increase in subjective well being during stress when tyrosine is preloaded (perhaps secondary to the antistress effects of tyrosine), although this is not overly reliable
grade-c Minor Moderate See 2 studies
Appears to preserve working memory during acute stressors without inherently having a memory boosting effect
grade-c - - See study
Depressive symptoms that occur during acute stressors have not been affected by Tyrosine supplementation; chronic depression not yet researched
grade-c - - See study
No significant influence has been noted on fatigue from L-Tyrosine supplementation during acute stresses
grade-c - - See study
No significant influences of Tyrosine on heart rate has been noted
grade-c - - See study
No significant influence on plasma noradrenaline levels (despite increased plasma tyrosine) during rest or during a cold stress test (which increases noradrenaline)

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Things to Note

Primary Function:

Do Not Confuse With

Taurine

Caution Notice

L-tyrosine has several theoretical interactions where caution is warranted. It may raise thyroid hormone production since it is a precursor for its synthesis, so those with a hyperactive thyroid should be wary. Also, it may interact with MAOIs leading to a hypertensive crisis. Additionally, it could theoretically block the uptake from the gut of some drugs that resemble certain amino acids such as levodopa. Finally, since it is a precursor for stimulatory neurotransmitters, it may interact with or potentiate the effects of other drugs or supplements that are stimulatory as well, along with drugs that affect dopamine and norepinephrine productions.

  • L-tyrosine is stimulatory. It may thus theoretically interact with other stimulatory pharmaceuticals or supplements.

  • L-tyrosine can theoretically interact with the absorption of some drugs that look like certain amino acids (e.g. levodopa). It can also theoretically interact with MAOIs and exacerbate hyperthyroid conditions.

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Click here to see all 50 references.