Tyrosine is a non-essential amino acid that the human body can synthesize on its own from the essential amino acid phenylalanine. In the field of sports nutrition, it is known as a dietary supplement that can influence our ability to react to stress and maintain mental alertness. Although there is scientific evidence to support this claim, L-tyrosine supplementation is not entirely without risk.
Role in hormone and neurotransmitter production
The importance of tyrosine lies in its function as a precursor for the synthesis of several critically important substances:
- Catecholamines: Tyrosine is essential for the formation of dopamine, epinephrine (adrenaline), and norepinephrine (noradrenaline). These substances play a key role in regulating bodily functions during physical stress and intense exercise.
- Thyroid hormones: This amino acid is also a precursor to the hormones triiodothyronine (T3) and thyroxine (T4), which are responsible for controlling overall metabolism.
Effects on the brain and cognitive functions
The mechanism of tyrosine's action is based on the fact that its increased intake in the form of dietary supplements (usually in doses of 5–10 g) increases its concentration in the blood and subsequently its transport across the blood-brain barrier into the brain. This increased amount of tyrosine in the brain can lead to enhanced synthesis of dopamine and norepinephrine directly in the central nervous system.
The most significant benefits of tyrosine have been observed in situations of acute and extreme stress:
- Improvement of cognitive function and mood: Research often conducted in military environments (Jongkees et al. 2015; Lieberman 2003) has shown that L-tyrosine supplementation can prevent reduced cognitive function and mood decline in acute stress situations.
- Mental resilience in challenging environments: (Banderet and Lieberman 1989) showed that tyrosine improves alertness, reaction time, pattern recognition, and complex cognitive tasks, such as reading from a map, in people exposed to a combination of extreme cold and high altitude (hypoxia).
Tyrosine in sports: Performance vs. mental capacity
Although the results in the area of mental resilience are promising, there is currently no evidence for direct increases in physical sports performance.
However, L-tyrosine supplementation is not without risks:
- Dosage of L-tyrosine: most dietary supplements do not contain it in sufficient amounts (usually up to 2 grams per dose) for this amino acid to have an effect on cognitive function or mood.
- Safety: Some experts warn that regular use of functional doses (5–10 g) could have adverse health effects, as these doses affect the activity of the sympathetic nervous system.
- Comparison with caffeine: caffeine has a similar effect on suppressing the decline in cognitive function during exercise and in many sports situations represents a more suitable and safer choice (Hogervorst et al. 2008).
Conclusion for athletes
Tyrosine can be an effective tool for improving or protecting cognitive abilities in acute stressful situations and physically demanding environments. However, its long-term supplementation can have a negative impact on our mental health. Currently, there is no evidence that L-tyrosine increases physical performance. From this perspective, caffeine is a far more suitable and safer choice for athletes.
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Sources of information
- Jongkees, B.J., B. Hommel, S. Kühn, and L.S. Colzato. 2015. Effect of tyrosine supplementation on clinical and healthy populations under stress or cognitive demands—a review. J Psychiatr Res 70:50-57.
- Lieberman, H.R. 2003. Nutrition, brain function and cognitive performance. Appetite 40(3):245-254.
- Banderet, L.E., and H.R. Lieberman. 1989. Treatment with tyrosine, a neurotransmitter precursor, reduces environmental stress in humans. Brain Res Bull 22(4):759-762.
- Jeukendrup, A., & Gleeson, M. (2025). Sport nutrition (4th ed.). Human Kinetics.
- Hogervorst, E., S. Bandelow, J. Schmitt, R. Jentjens, M. Oliveira, J. Allgrove, T. Carter, and M. Gleeson. 2008. Caffeine improves physical and cognitive performance during exhaustive exercise. Med Sci Sports Exerc 40(10):1841-1851.
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