L-tyrosine is a nonessential organic amino acid that is a building block of protein. It is an organic amino acid due to the presence of a carbon atom in its makeup.
It is a precursor of the neurotransmitter dopamine, as well as a precursor to the adrenal hormones norepinephrine and epinephrine.1 The body can make L-tyrosine from the amino acid phenylalanine. L-tyrosine rich foods include animal meat, wheat products, oatmeal and seafood.
What does it do and what scientific studies give evidence to support this?
L-tyrosine may help athletes avoid overtraining, due to its ability to offset fatigue.2 Because L-tyrosine is a precursor of Dopamine, supplementing with L-tyrosine may heighten mental alertness, increase feelings of well being, decrease feelings of depression, and offset physical and mental fatigue.3,4
Who needs it and what are some symptoms of deficiency?
Populations in need of L-tyrosine include: athletes, the obese or overweight, and the elderly. Hard training athletes may benefit from supplementing with L-tyrosine as it helps to offset fatigue and stress associated with intense training. L-tyrosine also serves to protect the integrity of the skin. Melanin, a substance which acts to protect the skin when the epidermis has been exposed to ultraviolet light, is derived from L-tyrosine. If a shortage of melanin is present within the body [because of a lack of L-tyrosine], skin defenses will be compromised. Melanin, which is derived from L-tyrosine, chemically reacts with sunlight to form a protective shield that protects the deeper layers of skin tissue.
Because persons suffering from depression frequently have low blood levels of this amino-acid, it may prove beneficial for members of this population to supplement with L-Tyrosine.5 People suffering from neurological degeneracy may also benefit from supplemental L-tyrosine.6
Members of the obese population may benefit from supplemental L-tyrosine. The thyroid is responsible for the manufacture of T-cells. L-tyrosine influences the manufacture of thyroxin [T-cells], which influences basal metabolic rate. Because of this, L-tyrosine may prove effective for weight loss. Individuals suffering from immune system destroying viruses like HIV, AIDS or hepatitis may find supplementing with L-tyrosine to be beneficial. Disease processes that ravage the immune system often induce catabolism, and thus muscle wasting. A loss of muscular protein results in increased for osteoporosis and bone fractures. To retain bodily protein, skeletal muscle, and thus anabolism, supplementing with L-tyrosine may be beneficial.
How much should be taken? Are there any side effects?
At this time clear dosing guidelines have not yet been established, so it is best to do what is known as "tolerance mapping".
Take a small dosage for one week, note the benefits and the side effects, and increase the dosage until the benefits are maximized and the side effects minimized. Over time the two will converge and you will hit the optimal dose. This process is similar to "receptor mapping" for bodybuilders who use insulin and steroids.
Many protein powders on the market are fortified with amino acids, including tyrosine. With this in mind, pay particular attention to how much tyrosine you are ingesting from all sources. No side effects have been reported, although as with any amino-acid, overdose is a possibility. Individuals suffering from psychiatric conditions should consult a qualified medical practitioner prior to the use of supplemental L-tyrosine.
If you do not feel comfortable following the above-described procedure, it is always best to follow the directions as prescribed on the products label.
Where can I get it?
There are many different brand names that manufacture supplemental L-Tyrosine.
1. Wurtman, RJ, and Lewis MC. Exercise, plasma composition and neurotransmission. In: Advances in Nutrition and Top Sport, edited by Brouns F.. Basel: Karger, 1991, vol. 32, p. 94-109.
2. Romanowski, W, and Grabiec S. The role of serotonin in the mechanism of central fatigue. Acta Physiol Pol 25: 127-134, 1974.
3. Lieberman, HR, Corkin S, Spring BJ, Wurtman RJ, and Growden JH. The effects of dietary neurotransmitter precursors on human behavior. Am J Clin Nutr 42: 366-370, 1985.
4. Banderet, LE, and Lieberman HR. Treatment with tyrosine, a neurotransmitter precursor, reduces environmental stress in humans. Brain Res Bull 22: 759-762, 1989.
5. Gelenberg AJ, Gibson CJ, Wojcik JD. Neurotransmitter precursors for the treatment of depression. Psychopharmacol Bull 1982;18:7-18.
6. Meyer JS, Welch KMA, Deshmuckh VD, et al. Neurotransmitter precursor amino acids in the treatment of multi-infarct dementia and Alzheimer's disease. J Am Geriatr Soc 1977;7:289-98.