L-tyrosine is a neutral amino acid, considered as non-essential. Our organism can indeed synthesize it in sufficient quantities from phenylalanine, an amino acid that contributes to the maintenance of normal organic functions in humans.
For adults, daily tyrosine and phenylalanine requirements are estimated at 14 mg/kg of body weight and a minimum of 1.1 g per day; in children aged between 3 months and 12 years, these figures vary from 22 to 125 mg/kg of body weight.
In the case of liver, kidney or phenylketonuria (a hereditary metabolic disease that prevents people suffering from converting phenylalanine into tyrosine, resulting in mental retardation and depigmentation of the skin and hair), the metabolism of certain amino acids is altered, making it necessary to take L-tyrosine.
L-tyrosine improves cognitive functions and increases resistance to effort by counteracting the negative effects of stress in particular. In fact, tyrosine is the precursor of catecholamines (dopamine, epinephrine, norepinephrine), neurotransmitters which help the organism to face emergency situations, in particular thanks to their actions on the cardiovascular system.
Also, a precursor of melanin, responsible for the pigmentation of the dander, L-tyrosine also plays a role in protection against UV rays.
Due to the involvement of this amino acid in many functions of the body, L-tyrosine supplementation of infant formula or clinical nutrition preparations is very useful.