Also known as: Tyrosine, N-Acetyl L-Tyrosine, NALT, 4-hydroxyphenylalanine
Cognitive & NootropicGood evidence
A precursor to dopamine, noradrenaline and adrenaline, useful specifically for maintaining cognitive performance under acute stress. Does little for a rested person, which is the key to using it sensibly.
Typical dose
500.0–2000.0 mg per day
30-60 minutes before the stressor, on an empty stomach
What it is
L-tyrosine is a non-essential amino acid, synthesised in the body from phenylalanine and obtained from protein foods including cheese, meat, fish, eggs and soy. Its name derives from the Greek for cheese, where it was first isolated.
It is the starting material for the catecholamine neurotransmitters: dopamine, then noradrenaline, then adrenaline. It is also a precursor for thyroid hormones and for melanin.
N-acetyl L-tyrosine, or NALT, is marketed as a more soluble and better-absorbed alternative. The evidence does not support this: conversion of NALT back to tyrosine in humans appears poor, and plain L-tyrosine raises plasma tyrosine more effectively. NALT is a case where the premium form is the worse choice.
How it works
Tyrosine is converted to L-DOPA by tyrosine hydroxylase, then to dopamine, and onward to noradrenaline and adrenaline. Under ordinary conditions this pathway is not limited by tyrosine availability, which is why supplementation does little for a rested, unstressed person.
Under acute stress the picture changes. Intense stressors such as cold, sleep deprivation, noise or high cognitive load accelerate catecholamine turnover, and synthesis can begin to fall behind depletion. In that state, additional tyrosine supports continued production.
This explains the pattern in the research precisely: benefits appear where catecholamines are being depleted faster than they are replaced, and disappear where they are not. Tyrosine restores capacity rather than enhancing it.
What the evidence shows
The research base is unusual, much of it conducted by military organisations interested in performance under extreme conditions. Trials involving cold exposure, sleep deprivation, sustained operations and multitasking under load have reported preserved cognitive performance and working memory with tyrosine.
Trials in rested participants performing ordinary cognitive tasks have generally found little or no benefit, which is entirely consistent with the mechanism rather than a contradiction of it.
Evidence for exercise performance is weak, and for mood there is little support despite the dopamine connection. Used for what it does, tyrosine has decent evidence; used as a general daily nootropic, it is likely to disappoint.
Dosing
Research protocols have typically used 100-150 mg per kilogram of bodyweight, which for an 80 kg person is 8-12 g. That is far above what most supplements provide.
Practical supplemental doses of 500-2,000 mg are common and better tolerated, though they sit well below the amounts used in the trials showing effect. This gap is worth knowing when judging whether a product is likely to do anything.
Take 30-60 minutes before the demanding period, on an empty stomach. Taken with a protein meal it competes with other amino acids for transport into the brain, which reduces the effect. Choose plain L-tyrosine over NALT.
At a glance
Common forms
L-tyrosine powder, L-tyrosine capsules, N-acetyl L-tyrosine (NALT), Within pre-workout and nootropic blends
Half-life / duration
Plasma tyrosine peaks 1-2 hours after ingestion
Timing
30-60 minutes before the stressor, on an empty stomach
Competition status
Permitted — not on the WADA Prohibited List
Category
Cognitive & Nootropic
Safety and side effects
Well tolerated at typical doses. Reported effects are mild and infrequent, including nausea, headache and, occasionally, feeling wired or restless.
The interactions that matter involve prescription medication. Tyrosine feeds production of the adrenaline family of neurotransmitters, so combining it with certain medicines can raise blood pressure sharply. It is also a building block for thyroid hormones, which matters if your thyroid function is being managed or medicated.
If you take any regular prescription medication, check before using supplemental tyrosine. It is not a neutral addition in the way it is often presented.
Who should avoid it
Do not use alongside prescription medication without your doctor's agreement — tyrosine feeds adrenaline production and can raise blood pressure sharply in combination with certain medicines. Speak to your doctor if your thyroid function is being monitored or medicated, since tyrosine is a building block for thyroid hormones. Not established for use in pregnancy or breastfeeding.
This entry is provided for information only. Food supplements should not be used as a substitute for a varied and balanced diet and a healthy lifestyle. Consult a qualified healthcare professional before use if you are pregnant, breastfeeding, taking medication or under medical supervision.
