Evidence Level
Moderate
L-Tyrosine is best supported for preserving cognitive performance under acute stress, with multiple military-funded studies demonstrating benefits during sleep deprivation, cold exposure, and multitasking. Its mechanism is straightforward: stress depletes catecholamines, and tyrosine provides the raw material for replenishment. Evidence for cognitive enhancement under normal, non-stressed conditions is much weaker — tyrosine is a "stress buffer" rather than a general cognitive enhancer.