• Tyrosine

    Supplement Forms/Alternate Names :

    • L-Tyrosine
    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.

    Therapeutic Uses

    Preliminary evidence, including small, double-blind trials, suggests that tyrosine supplements may help fight fatigue and improve memory and mental function in people who are deprived of sleep or exposed to other forms of stress . 1,10,12
    Based on the findings, mentioned in the above paragraph, it has been inferred that tyrosine might enhance alertness in people suffering from jet lag , but this has not been studied directly.
    Tyrosine may also provide some temporary benefit for attention deficit disorder (ADD) , but the benefits appear to wear off in a couple of weeks. 2,3,4 Tyrosine is said to work better for this purpose when it is combined in an "amino acid cocktail" along with gamma-aminobutyric acid (GABA), phenylalanine , and glutamine ; however, there is no scientific evidence to support this use.
    Although one extremely tiny study found tyrosine helpful for depression ; 5 a larger study found no evidence of benefit. 6
    Tyrosine has also been suggested for enhancing sports performance . However, in a double-blind study of 20 men, one-time use of tyrosine at a dose 150 mg per kilogram body weight failed to improve any measurement of muscular performance. 11

    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. 7 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. 10
    Depression  
    A pilot study that enrolled 9 individuals is widely quoted as proving that tyrosine can help depression. 8 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. 9

    Safety Issues

    Tyrosine seems to be generally safe, though at high dosages some people have reported nausea, diarrhea, vomiting, or nervousness. As with any other supplement taken in multigram doses, it is important to use a high-quality product; even a very small percentage of contaminant in the product might add up to a dangerous amount.
    Maximum safe dosages for young children, women who are pregnant or nursing, or those with severe liver or kidney disease have not been established.

    References

    1 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.

    2 Eisenberg MD, Asnis GM, van Praag HM, et al. Effect of tyrosine on attention deficit disorder with hyperactivity. J Clin Psychiatry. 1988;49:193-195.

    3 Reimherr FW, Wender PH, Wood RD, et al. An open trial of L-tyrosine in the treatment of attention deficit disorder, residual type. Am J Psychiatry. 1987;144:1071-1073.

    4 Wood RD, Reimherr FW, Wender PH, et al. Amino acid precursors for the treatment of attention deficit disorder, residual type. Psychopharmacol Bull. 1985;21:146-149.

    5 Gibson C, Gelenberg A. Tyrosine for the treatment of depression. Adv Biol Psychiatry. 1983;10:148-159.

    6 Gelenberg AJ, Wojcik JD, Falk WE, et al. Tyrosine for depression: a double-blind trial. J Affect Disord. 1990; 19:125-132.

    7 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.

    8 Gibson C, Gelenberg A. Tyrosine for the treatment of depression. Adv Biol Psychiatry. 1983;10:148-159.

    9 Gelenberg AJ, Wojcik JD, Falk WE, et al. Tyrosine for depression: a double-blind trial. J Affect Disord. 1990; 19:125-132.

    10 Deijen JB, Wientjes CJ, Vullinghs HF, et al. Tyrosine improves cognitive performance and reduces blood pressure in cadets after one week of a combat training course. Brain Res Bull. 1999;48:203-209.

    11 Sutton EE, Coill MR, Deuster PA, et al. Ingestion of tyrosine: effects on endurance, muscle strength, and anaerobic performance. Int J Sport Nutr Exerc Metab. 2005;15:173-85.

    12 Mahoney CR, Castellani J, Kramer FM, et al. Tyrosine supplementation mitigates working memory decrements during cold exposure. Physiol Behav. 2007 May 22. [Epub ahead of print]

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