Vitamins, Minerals and Dietary Supplements
What is tyrosine? Why 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.
