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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.

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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.

How to take it

Timing30-60 minutes before the demanding task or stressor - the tyrosine research shows an acute effect under load, not a background one.
With food?On an empty stomach, away from protein - dietary amino acids compete for the same transporter and dilute the effect.
Worth knowingThe doses that actually worked in research were 100-150 mg/kg of plain L-tyrosine, which for a 70 kg adult is 7-10 g - a 500 mg NALT capsule is nowhere near that, and plain L-tyrosine is cheaper and better supported.

Interactions

With medications

  • phenelzine, tranylcypromine and other MAO inhibitors

    Tyrosine is a catecholamine precursor and can contribute to a hypertensive reaction in someone whose monoamine breakdown is blocked. do not combine

  • levodopa

    Tyrosine and levodopa are both large neutral amino acids competing for the same intestinal and blood-brain barrier transporter, so tyrosine can reduce how much levodopa reaches the brain. separate by at least 2 hours, and discuss it with your neurologist

  • levothyroxine, and in hyperthyroidism generally

    Tyrosine is the precursor for thyroid hormone synthesis, so supplementation is a poor idea when thyroid output is already high or pharmacologically set. avoid it with untreated hyperthyroidism and discuss it before adding to thyroid hormone replacement

With other supplements

  • 5-HTP and L-tryptophan

    They compete with tyrosine for the same amino acid transporter into the brain, so taking them together blunts both. take them at different times of day

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

Is N-acetyl-L-tyrosine better than L-tyrosine?

No. A human infusion study found N-acetyl-L-tyrosine (NALT) was largely excreted unchanged rather than converted to tyrosine, and no oral study shows better delivery, so plain L-tyrosine is cheaper and better supported.

Does tyrosine help focus under stress?

Plain L-tyrosine has moderate evidence for preserving working memory during short-term stressors such as cold, noise or sleep loss, but not in rested people. No trial has tested N-acetyl-L-tyrosine itself for focus, mood or stress.

How much tyrosine do I need for an effect?

The research doses were 100-150 mg/kg of plain L-tyrosine, 7-10 g for a 70 kg adult, taken 30-60 minutes before a stressor. A 300-500 mg N-acetyl-L-tyrosine serving is nowhere near that.

Is N-acetyl-L-tyrosine safe with MAO inhibitors or thyroid medication?

No. Tyrosine, the component of N-acetyl-L-tyrosine that matters, is a catecholamine precursor that can contribute to a hypertensive reaction with MAO inhibitors, and it feeds thyroid hormone synthesis, so avoid it with hyperthyroidism and discuss it before adding to levothyroxine. It also competes with levodopa for absorption.

Scientific references

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