What is L-tyrosine? A plain guide

L-tyrosine is a non-essential amino acid — one of the twenty amino acids that build proteins, and one the body can make on its own, from another amino acid called phenylalanine. It's also the raw material the body uses to build the catecholamine neurotransmitters dopamine, norepinephrine and epinephrine, which is the reason it shows up in pre-workout blends, "focus" stacks and stress-related search results far more than most amino acids.

What it is, and where it comes from

The body gets tyrosine two ways: it converts phenylalanine into tyrosine using an enzyme called phenylalanine hydroxylase, and it absorbs tyrosine directly from protein-containing food. Because the body can make its own supply given enough phenylalanine, tyrosine is classified as "non-essential" (or conditionally essential) rather than an essential amino acid that must come entirely from the diet. It was first isolated from cheese in 1846, which is where its name comes from — tyros is Greek for cheese.

What it does in the body

Tyrosine's main job, from a research standpoint, is as the precursor of the catecholamines: dopamine, then norepinephrine, then epinephrine, made in that order by a chain of enzymes starting with tyrosine hydroxylase. A 2007 review of this pathway found that raising the amount of tyrosine available to the brain increases catecholamine production specifically in neurons that are actively firing — meaning the effect is tied to how active that neurotransmitter system already is, not a flat, always-on increase (PMID 17513421). Tyrosine also competes with several other large amino acids for the same transport system into the brain, so how much gets through depends partly on what else is circulating in the blood at the time.

Forms it's sold in

Most tyrosine supplements are the free amino acid, L-tyrosine, sold as capsules, tablets or powder. A second form, N-acetyl-L-tyrosine (NALT), is marketed as more water-soluble and easier to formulate into a drink or a smaller capsule. The research on that trade-off isn't encouraging: a 1989 study that infused N-acetyl-L-tyrosine directly into the bloodstream of 11 healthy volunteers found more than half of it was excreted unchanged in urine, with only a modest rise in usable tyrosine (PMID 2507878). A 1994 animal study feeding N-acetyltyrosine to piglets found the same pattern — 65% excreted unchanged — and worse nitrogen utilization than other tyrosine sources tested (PMID 7977717). Neither study tested an oral NALT supplement directly, but both point the same direction: NALT's water solubility doesn't appear to translate into better delivery of tyrosine itself.

Food sources

Tyrosine is present in most protein-containing foods: chicken, turkey, fish, eggs, dairy (cheese especially), soy, peanuts, almonds, pumpkin seeds, and whole grains, per USDA FoodData Central. A varied diet with adequate protein typically supplies tyrosine without needing to track it as its own nutrient, the way you might track something like iron or vitamin D.

Questions people ask

What is N-acetyl-L-tyrosine (NALT)?

It's a modified version of L-tyrosine with an acetyl group attached, made to dissolve in water more easily. The limited human and animal research that exists found it converts back into usable tyrosine inefficiently, with a large share excreted unchanged (PMID 2507878, PMID 7977717) — a reason plain L-tyrosine, not NALT, is what most of the cognitive-performance research below was actually tested with.

Does L-tyrosine increase dopamine?

It's the metabolic precursor of dopamine — the body converts tyrosine into L-DOPA and then dopamine using a chain of enzymes (PMID 17513421). That's a biochemical fact about the pathway, not proof that a capsule raises dopamine activity enough to produce a noticeable effect; see L-tyrosine benefits: what the research does and doesn't show for what's actually been tested in people.

Is L-tyrosine a stimulant?

No — it's an amino acid found in ordinary food, not a substance classified as a stimulant. A 2015 review of the cognitive research found tyrosine's measured effects mainly appeared when catecholamine activity was being depleted by stress, cold, or sleep loss, not as a general energizing effect in people who are already rested (PMID 26424423).

Does L-tyrosine help with tanning?

Tyrosine is also the amino acid an enzyme called tyrosinase uses to build melanin, the pigment responsible for skin and hair color — that's a basic fact of how melanin is made in the body, not evidence about a supplement. We found no controlled human trial testing whether oral tyrosine supplementation changes tanning or pigmentation, so there's no research basis to say it does.

Is L-tyrosine the same as tyrosine?

Yes. "Tyrosine" occurs in nature as the L-isomer almost exclusively, so "L-tyrosine" and "tyrosine" refer to the same molecule in this context; the "L-" is a chemistry naming convention, not a different substance.

What is L-tyrosine used for?

People search it out mostly for cognitive performance under stress, sleep loss, or demanding tasks — that's also what most of the clinical research has tested. See L-tyrosine benefits: what the research does and doesn't show for the trial-by-trial detail, and how much L-tyrosine should you take a day? for the doses those trials actually used.

Related reading: L-tyrosine benefits: what the research does and doesn't show, how much L-tyrosine should you take a day?, and how to choose a good L-tyrosine.