L-tyrosine is an amino acid the body uses to make the brain messengers dopamine and noradrenaline. As a supplement it is taken to stay sharp under stress or heavy mental load, and sometimes for exercise.
Also known as: tyrosine, N-acetyl L-tyrosine, NALT.
There is no intake value or upper limit. One exercise trial (Tumilty 2014) gave a single 150 mg per kg of body weight drink an hour before cycling. These are study protocols, not a recommendation.
It is sold in the US as a dietary supplement. Under the 1994 dietary supplement law (DSHEA), FDA does not approve dietary supplements before they are marketed, and the maker, not FDA, is responsible for safety and labeling.
What studies show: a 2015 review (Jongkees) concluded that tyrosine seems to help thinking mainly in short, stressful or demanding situations, and only when the person's brain chemistry is otherwise normal; it found limited promise for treating clinical disorders and minimal promise for physical exercise. In a small trial of 7 trained cyclists in 30°C heat, a single large dose did not change time-trial performance, heart rate or body temperature compared with placebo (Tumilty 2014).
The sources here are small and do not set out side effects or drug interactions, so the safety of regular use is not described by them.
We could not find a single published half-life or time to peak for L-tyrosine that applies to a supplement dose, so we do not list one. In one trial, blood levels of tyrosine relative to competing amino acids rose about 2.5-fold after a single dose and stayed up through 90 minutes of exercise (Tumilty 2014).
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