Tyrosine

Tyrosine is a precursor of the neurotransmitters norepinephrine and dopamine, which regulate mood, among other things. Tyrosine acts as a mood elevator; a lack of adequate amounts of tyrosine leads to a deficiency of norepinephrine in the brain, which in turn can result in depression. Tyrosine suppresses the appetite and helps to reduce body fat. Tyrosine aids in the production of melanin (the pigment responsible for skin and hair color) and in the functions of the adrenal, thyroid, and pituitary glands. It is also involved in the metabolism of the amino acid phenylalanine.

Tyrosine attaches to iodine atoms to form active thyroid hormones. Not surprisingly, therefore, low plasma levels of tyrosine have been associated with hypothyroidism. Symptoms of tyrosine deficiency can also include low blood pressure, low body temperature (such as cold hands and feet), and restless leg syndrome.

Supplemental L-tyrosine has been used for stress reduction, and research suggests it may be helpful against chronic fatigue and narcolepsy. It has been used to help individuals suffering from anxiety, depression, allergies, and headaches, as well as persons undergoing withdrawal from medications. It may also help people with Parkinson's disease.

Natural sources of tyrosine include almonds, avocados, bananas, dairy products, lima beans, pumpkin seeds, and sesame seeds. Tyrosine can be also be produced from phenylalanine in the body. Supplements of L-tyrosine should be taken at bedtime or with a high-carbohydrate meal so that it does not have to compete for absorption with other amino acids.

Persons taking monoamine oxidase (MAO) inhibitors, commonly prescribed for depression, must strictly limit their intake of foods containing tyrosine and should not take any supplements containing L-tyrosine, as it may lead to a sudden and dangerous rise in blood pressure. Anyone who takes prescription medication for depression should discuss necessary dietary restrictions with his or her physician.

People born with the genetic condition phenylketonuria (PKU) are unable to metabolize the amino acid phenylalanine. Mental retardation and other severe disabilities can result. While phenylalanine restriction prevents 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, although the evidence remains contradictory.

Where is it found ?

Tyrosine is found in: dairy products, meats, fish, wheat, oats, and many other foods contain tyrosine.

Who is likely to be deficient ?

Some people affected by PKU are deficient in tyrosine. Tyrosine levels are sometimes low in depressed peoples.  Any person losing large amounts of protein, such as those with some kidney diseases, may be deficient in several amino acids, including tyrosine.

How much to take

Most people should not supplement tyrosine. Some human research with people suffering from a variety of conditions use the equivalent of 7 grams per day. A useful amount in people with PKU remains uncertain. In that case, monitoring of blood levels by a nutritionally oriented physician is recommended.

Side effects

Tyrosine is not generally associated with side effects. Vitamin B6, folic acid, and copper are necessary for conversion of tyrosine into neurotransmitters.

Caution

Contraindicated for people with pigmented malignant melanomas. Tyrosine may increase blood pressure. Not to be taken with antidepressants and MAO inhibitors, St. John's wort or licorice root.

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