Tyrosine is the dietary precursor of the catecholamine norepinephrine, a key brain neurotransmitter that is critical for the central nervous system (CNS) response to various types of acute stress. Psychological stress increases catecholamine turnover in the brain, increasing the requirement for tyrosine to support synthesis of norepinephrine. Animal and human studies have shown that tyrosine supplementation can produce beneficial effects on cognitive and physiological functions during exposure to a variety of acute stressors.