Ingredient Evidence Review
L-tyrosine (free form)
L-tyrosine (amino acid)
Last updated 2026-05-19 · 3 primary citations
Mechanism
Tyrosine is an amino acid your brain converts directly into dopamine and norepinephrine — the chemicals behind focus, drive, and stress tolerance. Under heavy mental load you burn through them faster than you make them, and supplemental tyrosine refills the supply.
Why we use it
Catecholamine availability is the limit on sustained executive function under stress. Thomas 1999 military trials established free-form tyrosine at the gram scale.
How we dose it
Hericea uses 2,000 mg per serving (per AM stick pack). The clinical trial range that anchors this dose is 100–2,000 mg/day.
Free-form L-tyrosine (NOT N-acetyl-L-tyrosine — that form has poor cognitive bioavailability per Thomas 1999 military stress trials).
Quality & sourcing
Pharma-grade free-form L-tyrosine. NOT NALT.
Pharma-grade USP.
Cautions
- consult physicianConsult physician if on MAOI antidepressants.
- consult physicianAvoid if you have hyperthyroidism or melanoma history.
Primary literature
Thomas et al. (1999)
Pharmacol Biochem BehavRCT
L-tyrosine improved cognitive performance under military stress.
PMID 10548261
Steenbergen L et al. (2015)
NeuropsychologiaRCT
L-tyrosine improved cognitive flexibility on demanding task-switching.
PMID 25598314
Hase et al. (2015)
Pharmacol Biochem BehavRCT
L-tyrosine improved working memory under stress.
PMID 25797188