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.

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.

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

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).

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 [show legend]
	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
	Cognition	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.
	Blood Pressure	-	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.
	Stress	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
	Subjective Well-Being	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
	Working Memory	Minor	Moderate See 2 studies	Appears to preserve working memory during acute stressors without inherently having a memory boosting effect
	Depression	-	- See study	Depressive symptoms that occur during acute stressors have not been affected by Tyrosine supplementation; chronic depression not yet researched
	Fatigue	-	- See study	No significant influence has been noted on fatigue from L-Tyrosine supplementation during acute stresses
	Heart Rate	-	- See study	No significant influences of Tyrosine on heart rate has been noted
	Noradrenaline	-	- See study	No significant influence on plasma noradrenaline levels (despite increased plasma tyrosine) during rest or during a cold stress test (which increases noradrenaline)