Tyrosine (alternative name L-Tyrosine) is one of the 22 amino acids that are used by the cells to synthesize proteins. Tyrosine is a nonessential amino acid because the body can make it from another amino acid phenylalanine .
Tyrosine and Exercise
Tyrosine is a precursor to some hormones and neurotransmitters (epinephrine, norepinephrine, and dopamine) . It is believed that inadequate production of these hormones and neurotransmitters could reduce physical performance . Therefore, tyrosine has been suggested to be ergogenic .
Acute tyrosine supplementation doesn’t seem to improve the mood, psychomotor performance or dopamine-dependent cognition . A study by Chinevere and associates  noted that tyrosine supplementation did not enhance performance during a cycling time trial. Furthermore, a double-blind, crossover study by Sutton and colleagues  found that tyrosine supplementation (150 mg/kg) significantly increased plasma tyrosine levels, but had no significant ergogenic effects (endurance, power, or muscle strength) in healthy men.
Exercise in the heat may become limiting to the dopamine synthesis due to heat stress and extreme demands of exercise. Therefore, Tumilty et al.  hypothesized that subjects would cycle for longer in combination with tyrosine supplementation in a warm (30°C) environment. The results showed that tyrosine supplementation is associated with increased endurance capacity in the heat in trained individuals. However, a more recent study demonstrated that contrary to the hypothesis, an acute administration of tyrosine did not improve self-paced exercise performance in the heat compared with a placebo .
Despite many athletes claim that tyrosine supplementation helps their performance there is no evidence to support this. More research is needed to better evaluate its use as an ergogenic aid.
Other Uses and Benefits
Under stress, the body isn’t able to make enough tyrosine . This has led some researchers to believe that it may help improve memory and performance under psychological stress, due to its involvement in the production of epinephrine and norepinephrine .
Magill and others  tested a few nutrients on cognitive and motor performance after sleep deprivation. Although amino acid tyrosine was less effective than amphetamine, it improved performance on several tests and researchers suggested it deserves further testing .
Tyrosine Side Effects and Safety
There is a lack of safety data on long-term L-tyrosine use in healthy people . Supplementing with 2,5 grams 3 times daily for two weeks had no beneficial or adverse effects . Tyrosine seems to be safe when used in doses up to 150 mg/kg per day for up to 3 months.  Some people experience side effects such as nausea, headache, fatigue, and joint pain .
- University of Maryland Medical Center. Retrieved from http://www.umm.edu/ at 10. May 2013
- Williams, Melvin. “Dietary supplements and sports performance: amino acids.” J Int Soc Sports Nutr 2.2 (2005): 63-67.
- Tumilty, Les, et al. “Oral tirozine supplementation improves exercise capacity in the heat.” European journal of applied physiology 111.12 (2011): 2941-2950.
- Chinevere, Troy D., et al. “Effects of L-tyrosin and carbohydrate ingestion on endurance exercise performance.” Journal of Applied Physiology 93.5 (2002): 1590-1597.
- Sutton, E., et al. “Ingestion of tyrosine: Effects on endurance, muscle strength, and anaerobic performance.” International Journal of Sport Nutrition and Exercise Metabolism 15:173-85, 2005.
- Magill, Richard A., et al. “Effects of tyrosine, phentermine, caffeine D-amphetamine, and placebo on cognitive and motor performance deficits during sleep deprivation.” Nutritional neuroscience 6.4 (2003): 237-246.
- Young, Simon N. “L-Tirosine to alleviate the effects of stress?.” Journal of Psychiatry & Neuroscience 32.3 (2007): 224.
- Find a Vitamin or Supplement. Retrieved from WebMD.com at 10. May 2013
- Tumilty, Les, et al. “Failure of oral tyrosine supplementation to improve exercise performance in the heat.” Medicine & Science in Sports & Exercise 46.7 (2014): 1417-1425.