Tyrosine

What is tyrosine

Tyrosine is a very important amino acid for the human body; its dietary intake is not essential but may become so in conditions of phenylalanine deficiency.

In addition to being derived from food, tyrosine can in fact be synthesized from phenylalanine, simply by adding a hydroxyl group (OH) to its aromatic ring. As the latter is an essential amino acid, tyrosine is included in the category of semi-essential amino acids.

Functions and potential benefits

Tyrosine is the starting amino acid for the synthesis of important neurotransmitters, such as dopamine, adrenaline and noradrenaline. These last two substances are very important for the process of adaptation to intense and sudden psychophysical stress. For this reason tyrosine are ascribed adaptogenic properties, useful for improving the body's response to various types of stress. No coincidence that this amino acid was taken at high doses by the pilots of the fighter-bombers engaged in the Falklands war, in order to stay awake longer and raise the threshold of attention.

Since tyrosine is a precursor to dopamine and norepinephrine, whose levels tend to be low in depressed people, the integration of this amino acid has been proposed as an adjuvant for the treatment of minor depressive episodes.

Tyrosine is also necessary for the synthesis of melanin, the skin pigment responsible for tanning and skin color, but also for the eyes and hair. It also participates in the synthesis of various hormones, such as thyroid ones, as well as intervening in protein synthesis and thus re-entering most of the body's protein structures.

The therapeutic or supplementary doses normally recommended are 500-1000 mg of L-tyrosine, to be taken three times a day before the main meals. To improve the waking state, reducing the need for sleep, dosages in the order of 150 mg per kg of body weight are recommended.

Tyrosine deficiency

Tyrosine deficiencies are rather rare and are mostly associated with calorie-protein malnutrition. Low levels of this amino acid have been associated with hypotension, low body temperature and hypothyroidism.

Tyrosine deficiency may occur in individuals with phenylketonuretics, due to the need to completely remove all dietary sources of phenylalanine from their diet. The deficit is compensated by inserting the amino acid in the amino acid supplements that these individuals are forced to take on a daily basis in large quantities.

Excess of tyrosine

Excessive intake of tyrosine has been linked to eye injuries, growth retardation, and decreased appetite. However, tyrosine is generally well tolerated and only a small percentage of individuals have complained of problems with nausea, headache, fatigue, heartburn and joint pain after taking it.

Tyrosine in foods

The tyrosine-producing foods include soy products, fish, chicken, turkey, almonds, bananas, milk and its derivatives, sesame seeds, avocado and pumpkin seeds.

Precautions for use

Caution is advised if you wish to take tyrosine supplements in the presence of headaches and migraines, as the amino acid may exacerbate these disorders (increasing tyramine synthesis). For the same reason, use in combination with MAO inhibitory drugs (risk of hypertensive crisis with cardiac damage) should be avoided; these drugs include isocarbossazide, phenelzine, selegiline, moclobemide and tranylcypromine. Prudence also in hyperthyroid subjects, suffering from Basedow's disease or taking drugs against hypothyroidism such as thyroxine (eutirox); finally, the intake of tyrosine must be absolutely prohibited during treatment with levodopa (an antiparkinsonian drug), given the competition for absorption at the intestinal level.