Tyrosine is non-essential amino acid because it is synthesized in the body from phenylalanine. Tyrosine has a sparing action, because if tyrosine is fed then phenylalanine- need of the body is decreased. Tyrosine has got an immense metabolic role in the body. It is ketogenic as well as glycogenic.
Both phenylalanine and tyrosine are metabolized through the common pathways. Phenylalanine is initially but irreversibly hydroxylated to tyrosine. Tyrosine then undergoes series of metabolic changes leading to the formation of hormones and melanin.
Tyrosine was first isolated from casein in 1849 and is abundant in insulin as well as the enzyme papain and can be synthesized from the amino acid phenylalanine in the body.
It is a precursor of the neurotransmitters epinephrine, nor epinephrine and dopamine, all of them extremely important in the brain and transmits nerve impulses and prevents depression. Dopamine is also vital to mental function and seems to play a role in sex drive.
L-Tyrosine is formed by skin cells into melanin, the dark pigment that protects against the harmful effects of ultraviolet light. Thyroid hormones, which have a role in almost every process in the body, also contain tyrosine as part of their structure.
Tyrosine and tryptophan have with been used with some success in the treatment of cocaine abuse and in another study it was combined with the antidepressant Imipramine to treat chronic cocaine abuse where it was reported that the combination blocked the cocaine high and prevented the severe depression that accompanies withdrawal.
Sources of tyrosine
L-tyrosine is found in many protein containing foods, such as meats, dairy products, fish, wheat and oats.
Benefits of tyrosine
The action of this amino acid in brain functions is clear with its link to dopamine as well as nor epinephrine, but it is also helpful in suppressing the appetite and reducing body fat, production of skin and hair pigment, the proper functioning of the thyroid as well as the pituitary and adrenal gland.
It is used for stress reduction and may be beneficial in narcolepsy, fatigue, anxiety, depression, allergies, headaches as well as drug withdrawal. In a study, using soldiers, tyrosine proved effective in alleviating stress and keeping them more alert.
Other possible benefits of tyrosine include helping to calm the body, increase energy and enhance libido. It is also converted into the skin pigment melanin that protects the skin from harmful UV light rays.
L-tyrosine is thought to specifically affect several health conditions, particularly Parkinson’s disease and certain mood disorders. Supplements may be useful for people with these conditions as well. Several studies have also indicated that l-tyrosine benefits people with Alzheimer’s disease and dementia.
Tyrosine has also been used to help women with pre-menstrual distress who were also found to have very low levels of tyrosine. Women taking birth-control pills also were found to have very low levels of tyrosine. The researchers concluded that there was a clear trend relating pre-menstrual distress to decreased tyrosine levels.
Deficiency symptoms of tyrosine
Tyrosine, a parent amino acid for skin, hair, and eye pigments and is involved in syndromes, known generally as oculocutaneous albinism, that are characterized by the failure to form melanin pigments, resulting in partial or complete albinism.
It is also the precursor amino acid for the thyroid gland hormone thyroxin, and a defect in this may result in hypothyroidism - an enlargement of the thyroid gland (goiter), severe growth failure, and retardation of central nervous system development.
A deficiency may also have symptoms of low blood pressure, low body temperature (including cold hands and feet) and "restless leg syndrome".
Symptoms of high intake
It is also important to note that l-tyrosine may interact with certain medications. Anyone taking prescription drugs should consult a physician about possible l-tyrosine side effects and interactions.
Daily requirement
Daily requirement levels are not confirmed but some experiments have been performed with people taking up to 5 - 7 grams per day, with no confirmed toxic levels, but people taking MAO inhibitors, who suffer from high blood pressure and have problems with skin cancer should not take supplementation of L-tyrosine, and should aim to limit their intake of food sources high in this nutrient.
L tyrosine supplements are not necessary for most people, but those with specific conditions that may be related to deficiencies of l-tyrosine may benefit from taking 100 mg per 2.2 pounds of body weight.
Some other points
If taking a tyrosine supplement it is best to take it at bedtime, or with a high carbohydrate meal to prevent competition of absorption with other amino acids. Folic acid, copper and vitamin B6 is a good combination to have with this nutrient to maximize absorption and effectiveness
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