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Tyrosine is an amino acid found in meat proteins. Your body uses it as a starting material to make several neurotransmitters (chemicals that help the brain and nervous system function). Based on this fact, tyrosine has been proposed as a treatment for various conditions in which mental function is impaired or slowed down, such as fatigue and depression. It has also been tried for attention deficit disorder (ADD).
Sources
Your body makes tyrosine from another common amino acid, phenylalanine, so deficiencies are rare; however, they can occur in certain forms of severe kidney disease as well as in phenylketonuria (PKU), a metabolic disorder that requires complete avoidance of phenylalanine.
Good sources of tyrosine include dairy products, meats, fish, and beans.
Therapeutic Dosages
The typical therapeutic dosage of tyrosine used in studies ranges from 7 g to 30 g daily.
What Is the Scientific Evidence for Tyrosine?
*Sleep Deprivation *
A double-blind, placebo-controlled study that enrolled 20 US Marines suggests that tyrosine can improve mental alertness during periods of sleep deprivation. 1 In this study, the participants were deprived of sleep for a night and then tested frequently for their alertness throughout the day as they worked. Compared to placebo, 10 g to 15 g of tyrosine given twice daily seemed to provide a "pick-up" for about 2 hours.
Similar benefits were seen with 2 g of tyrosine daily in a double-blind, placebo-controlled trial of 21 military cadets exposed to physical and psychological stress. 2
*Depression *
A pilot study that enrolled 9 individuals is widely quoted as proving that tyrosine can help depression. 3 However, this study was too small to provide reliable results. A subsequent double-blind, placebo-controlled study of 65 people with depression failed to find any benefit. 4
References
- Neri DF, Wiegmann D, Stanny RR, et al. The effects of tyrosine on cognitive performance during extended wakefulness. Avit Space Environ Med. 1995;66:313-319.
- Deijen JB, Wientjes CJ, Vullinghs HF, Cloin PA, Langefeld JJ. Tyrosine improves cognitive performance and reduces blood pressure in cadets after one week of a combat training course. Brain Res Bull. 48(2):203-9.
- Gibson C, Gelenberg A. Tyrosine for the treatment of depression. Adv Biol Psychiatry. 1983;10:148-159.
- Gelenberg AJ, Wojcik JD, Falk WE, Baldessarini RJ, Zeisel SH, Schoenfeld D, Mok GS. Tyrosine for depression: a double-blind trial. J Affect Disord. 19(2):125-32.
