L-tyrosine is an amino acid synthesized in the body and also found in chicken, turkey, fish, dairy products and most other high-protein foods. It is involved in the structure of almost every protein in the body, and is an essential component for the production of several important brain chemicals known as neurotransmitters, which help nerve cells to communicate. Supplementation with L-tyrosine has been shown to enhance various aspects of cognitive performance including alertness, attention, focus, memory, cognitive flexibility, reaction time and vigilance.