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Vitamins, Minerals and Dietary Supplements

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Tyrosine

What is tyrosine? What do we need it?

Tyrosine is a non-essential amino acid that the body synthesizes from phenylalanine, another amino acid. It plays a role in the structure of nearly every protein in the body, and is a precursor of several other substances, including dopamine, norepinephrine and epinephrine.

Through its association with neurotransmitters and hormones, tyrosine is considered vital to normal mental function and alertness. Some studies have shown that tyrosine may reduce the symptoms of Parkinson’s disease, combat depression and alleviate environmental and psychological stress. Skin cells also use tyrosine to help create melanin, the dark pigment that protects the skin against the negative effects of ultraviolet light.

Some people are born with a genetic condition called phenylketonuria (PKU), which leaves them unable to metabolize the amino acid phenylalanine. This condition can cause mental retardation and other severe disabilities. While restricting phenylalanine from the diet can prevent these problems, it also leads to low tyrosine levels in many -- but not all -- people with PKU. Tyrosine supplementation may be beneficial in some people with PKU.

How much tyrosine should I take?

Because tyrosine is a non-essential amino acid, daily recommended allowances and requirements have yet to be established. Most people should not supplement with tyrosine. People with phenylketonuria may consider supplementing with tyrosine but should consult with a qualified health practitioner first.

What are some good sources of tyrosine? What forms are available?

Tyrosine can be found in dairy products, fish, meat and some grains, such as wheat and oats. It is also sold as an individual supplement or in conjunction with other amino acids.

What can happen if I don't get enough tyrosine? What can happen if I take too much? Are there any side-effects I should be aware of?

Tyrosine deficiency is common in people with phenylketonuria (PKU); many depressed people also report low tyrosine levels. A lack of tyrosine may cause a variety of conditions, including muscle loss, weaknes, low protein levels, mood disorders and liver damage. There are no known signs of toxicity from tyrosine; however, patients who are allergic to certain food proteins may want to avoid tyrosine supplements.

Tyrosine may increase the effect of some antidepressants. Make sure to consult with a qualified health care provider before taking tyrosine supplements.

References

  • 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—9.
  • Dollins AB, Krock LP, Storm WF, et al. L-tyrosine ameliorates some effects of lower body negative pressure stress. Physiol Behav 1995;57:223—30.
  • Koch R. Tyrosine supplementation for phenylketonuria treatment. Am J Clin Nutr 1996;64:974—5.
  • Neri DF, Wiegmann D, Stanny RR, et al. The effects of tyrosine on cognitive performance during extended wakefulness. Aviat Space Environ Med 1995;66:313—9.
  • Shurtleff D, Thomas JR, Schrot J, et al. Tyrosine reverses a cold-induced working memory deficit in humans. Pharmacol Biochem Behav 1994;47:935—41.

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