L-Tyrosine is a non-essential amino acid found naturally in cheese products and is a precursor to dopamine, a neurotransmitter implicated in mood improvement and the treatment of Parkinson's disease. Normal dosing ranges vary from 500 mg to 2 grams or more to help balance neurotransmitter pools. Tyrosine is orally bio-available and frequently used for cognitive improvement in certain populations. Although there is some question the amount of orally digested L-tyrosine reaching the brain, it is the foundation of many nootropic stacks (nutraceuticals used to improve mood or so-called smart drugs).
The rate of L-tyrosine to dopamine conversion is regulated by the body, so L-tyrosine is relatively safe. The supplement may provide peripheral stimulation as well, offering athletes an edge in their training performance. All in all, tyrosine is an excellent supplement with a large body of research. The molecule is also found in various whey protein isolates and concentrates. Despite L-tyrosine being a "non-essential" amino acide, mice with profound depletion of L-tyrosine present with various abnormalities, and supplementation of this molecule enhances their cognitive processes back to baseline. Dopamine receptors are subject to tolerance, so users may need to escalate dosing regimens when the effects wear off. The supplement's effects are relatively short-lived due to endogenous metabolism, so once daily or multi-dosing is required.