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L-tyrosine

In small trials, L-tyrosine limited the decline in memory and attention during stress situations: cold, sleep deprivation, military training. For sports, a meta-analysis of 8 studies found no effect on endurance.

Benefits

• Memory in the cold: in 8 men exposed to 4 °C, 150 mg per kilo taken 2 hours prior restored the accuracy of a memory test to the level measured at 22 °C.
• Sleep deprivation: after a sleepless night, 150 mg per kilo improved a psychomotor task and reduced errors in a vigilance task.
• Military stress: in 21 cadets undergoing combat training, a beverage providing 2 g of tyrosine per day for 5 days improved a memory test and a visual tracking test, and lowered systolic blood pressure.
• Intense noise: in 16 young adults, 100 mg per kilo improved two mental tasks sensitive to stress and lowered diastolic blood pressure.
• Multitasking: in 20 adults, 150 mg per kilo taken 1 hour before made working memory more accurate when other tasks were performed at the same time, without changing anything for simple tasks.
• Mental flexibility: in 22 adults, tyrosine reduced the cost of switching from one task to another compared to a placebo.
• Cycling after mental fatigue: in 12 recreational cyclists, 300 mg per kilo increased pedaling time to exhaustion by 16 % (460 versus 399 seconds), with a perceived exertion that rose less quickly.
• Heat: in 8 men cycling at 30 °C, 150 mg per kilo taken 1 hour before allowed them to last 80.3 minutes versus 69.2 minutes under placebo.