L-Tyrosine
N-Acetyl L-Tyrosine (NALT)
L-Tyrosine is a conditionally essential amino acid and direct precursor to the catecholamine neurotransmitters dopamine, norepinephrine, and epinephrine. It is primarily used to support cognitive performance, mood, and stress resilience, particularly under conditions of acute stress, sleep deprivation, or high cognitive demand. N-Acetyl L-Tyrosine (NALT) is an acetylated form marketed for enhanced bioavailability, though evidence suggests L-Tyrosine may actually yield higher plasma tyrosine levels per gram administered.
Mechanism of Action
L-Tyrosine is hydroxylated by tyrosine hydroxylase to L-DOPA, the rate-limiting step in catecholamine synthesis, which is then converted to dopamine, norepinephrine, and epinephrine. Under conditions of high neuronal firing or stress, catecholamine stores can become depleted; supplemental tyrosine replenishes the substrate pool and helps maintain neurotransmitter synthesis capacity. It also serves as a precursor to thyroid hormones (T3 and T4) and melanin, contributing to broader physiological roles beyond neurotransmission.
Evidence by Health Goal(13 goals)
Dosing Protocols
30-60 minutes before a stressful event, cognitive task, or exercise on an empty stomach; avoid taking with high-protein meals that compete for absorption via large neutral amino acid transporters
Cycle: null
NALT doses are lower due to higher solubility but may not translate to proportionally higher plasma tyrosine. For chronic daily use, start at the lower end (500mg L-Tyrosine or 300mg NALT). Acute stress-dosing studies have used up to 100-150mg/kg bodyweight in military contexts, though 1-2g is sufficient for most individuals.
Safety & Side Effects
L-Tyrosine has a well-established safety profile at typical supplemental doses (500-2000mg) and is generally well tolerated in healthy adults. Caution is warranted in individuals with hyperthyroidism, melanoma, phenylketonuria (PKU), or those taking MAOIs or thyroid medications, as these conditions represent contraindications or significant interaction risks.
Possible Side Effects
- !Gastrointestinal discomfort, nausea, or reflux at doses above 2g
- !Headache, particularly when taken without adequate hydration
- !Insomnia or sleep disruption if taken in the evening due to stimulatory catecholamine activity
- !Restlessness or mild anxiety in sensitive individuals or at high doses
- !Elevated blood pressure due to increased norepinephrine synthesis
- !Migraine triggering in susceptible individuals via tyramine-adjacent pathways
- !Potential worsening of hyperthyroid symptoms due to thyroid hormone precursor activity
Interactions
- -MAO inhibitors (MAOIs): Combined use can cause dangerous hypertensive crisis due to impaired catecholamine breakdown — contraindicated
- -Levodopa (L-DOPA): Competes for the same large neutral amino acid transporters, potentially reducing levodopa absorption and efficacy — avoid co-administration
- -Thyroid medications (levothyroxine): Tyrosine is a precursor to T3/T4; may additively influence thyroid hormone levels — use caution and monitor thyroid function
- -Stimulant medications (amphetamines, methylphenidate): Additive catecholaminergic activity may increase cardiovascular strain and anxiety
- -High-protein meals or other large neutral amino acids (leucine, phenylalanine): Compete for intestinal and blood-brain barrier transport, significantly reducing uptake — take on an empty stomach
Cost & Where to Buy
Bulk L-Tyrosine powder is inexpensive at $8-12/month; capsule forms from branded manufacturers range $15-25/month. NALT is slightly pricier per gram but lower doses offset the cost. No prescription required.
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