L-tyrosine is a unique nootropic: The more demanding the situation, the more effective it becomes. This is due to its neuropharmacological properties of being a conditionally essential amino acid. Only under significant stress does it becomes an essential precursor for the vital neurotransmitters dopamine and noradrenaline (1). This implies that L-tyrosine may have powerful concentration-enhancing properties.

In a cross-over trial, those ingesting a high dose of 150mg/kg of L-tyrosine performed better in a stressful multi-task environment one hour later compared to placebo, with no difference being observed between the two groups in a less stressful single-task scenario (2). Another study showed a significant lack of decline of psychomotor function and vigilance in sleep-deprived conditions (3). A summary literature review concluded that L-tyrosine is an effective cognitive enhancer, but only in states of temporary dopamine and noradrenaline depletion (4).

The above studies highlight L-tyrosine as a nootropic with great potential, particularly for those with high-demand jobs requiring laser-sharp focus. Reassuringly, a literature review has found no evidence of safety concerns in humans (4).