Supplement analysis backed by scientific evidence · PT

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Limited evidenceBrain & cognition

N-Acetyl-L-Tyrosine

A more soluble form of tyrosine sold for stress and focus. Plain tyrosine has reasonable evidence under acute stress, but the acetylated form is poorly converted back to tyrosine in humans.

Evidence last reviewed: August 2026

What the science says

  • Poor conversion to tyrosine Limited evidence

    A human infusion study found that N-acetyl-L-tyrosine was largely excreted unchanged in urine rather than being converted to free tyrosine, making it an inefficient tyrosine source. The study used intravenous administration, so oral behaviour may differ, but no oral study has shown better delivery than plain tyrosine.

  • Tyrosine itself under acute stress Moderate evidence

    A review of tyrosine supplementation concluded that it can preserve working memory and cognitive flexibility during short-term stressors such as cold, noise or sleep loss, while showing no benefit in rested, unstressed people. This evidence belongs to L-tyrosine, not to the acetylated form.

  • Focus and mood claims Limited evidence

    No randomized trial has tested N-acetyl-L-tyrosine specifically for attention, mood or stress in humans.

Dosage & safety

Studied doseLabels typically give 300–500 mg of N-acetyl-L-tyrosine per serving. The doses that worked in tyrosine research were far larger — roughly 100–150 mg/kg body weight of L-tyrosine, taken 30–60 minutes before a stressor.
SafetyGenerally well tolerated; nausea, headache and heartburn are reported at high doses. Tyrosine should be avoided or used cautiously with MAO inhibitors and with levodopa, and by people with hyperthyroidism or on thyroid hormone, since tyrosine is a precursor for thyroid hormones and catecholamines. Not established in pregnancy.

Scientific references

Where to buy

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