Supplements

Tyrosine

Tyrosine is a nonessential amino acid. It is synthesized in the body from phenylalanine and is a precursor of adrenaline (epinephrine), norepinephrine, dopamine, thyroid hormones, and some types of estrogen. In order for tyrosine to metabolize into these substances, folic acid, niacin, vitamin C, and copper are needed.

Low levels of tyrosine can lead to deficiencies in norepinephrine and dopamine-neurotransmitters that regulate mood. Depression can result. Animal studies have demonstrated that stressed animals have reduced levels of norepinephrine; however, administration of tyrosine prevented a norepinephrine deficiency. Tyrosine deficiency is also associated with low blood pressure, low body temperature, and restless leg syndrome.

Tyrosine aids in the production of melanin (pigment responsible for hair and skin color) and in the functions of the adrenal, thyroid, and pituitary glands. Tyrosine attaches to iodine atoms to form active thyroid hormones. A deficiency of tyrosine has been associated with hypothyroidism.

Tyrosine also acts as a mild antioxidant, suppresses the appetite, and helps to reduce body fat.

Because tyrosine binds unstable molecules that can potentially cause damage to the cells and tissues, it is considered a mild antioxidant. Thus, it may be useful in heavy smokers and in individuals exposed to chemicals and radiation.

Acetyl L-tyrosine (ALT) travels to the brain easier than any other form. Its impact on clinical depression is a significant contribution to nutritional medicine. The most pronounced effect is on depressive states characterized by apathy, lethargy, and listlessness. For the agitated, overwrought type of depression, tryptophan and 5-hydroxy-tryptophan, work better.

Studies that verified tyrosine's psychological lift, even against serious cases of depression, used doses of 600-2,000 mg per day. Some people showed signs of feeling better within a week. Dosages can be scaled down, to perhaps 300 mg once or twice a day, by using acetyl L-tyrosine.

In conjunction with tryptophan, tyrosine affects several other illnesses that stem from a brain chemistry imbalance, including attention deficit/hyperactivity disorder, Parkinson's disease, and withdrawal from cocaine addiction.

The drug L-dopa is usually prescribed by physicians to help control the trembling, rigidity, and other symptom's of Parkinson's disease, some research suggests that tyrosine, along with other medications, could improve the therapy.

Supplemental L-tyrosine has been used for stress reductions, and research suggests it may be helpful against chronic fatigue and narcolepsy.

L-tyrosine supplementation can help reduce the irritability, depression, and fatigue associated with PMS. Tyrosine appears to help individuals with low sex drive by stimulating the libido.

Deficiency: Symptoms of tyrosine deficiency can include low blood pressure, low body temperature (such as cold hands and feet), and restless leg syndrome.

Sources: Natural sources of tyrosine are found in almonds, avocados, bananas, dairy products, lima beans, pumpkin seeds and sesame seeds.

Tyrosine can also be produced from phenylalanine in the body.

Precautions: Persons taking monamine 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 taking prescription medication for depression should discuss dietary restrictions with their physician.

Other possible side effects are migraine headache, high blood pressure, mild gastric upset, and a promoter of cancer cell division.

Dosage Ranges and Duration of Administration: 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.

• For depression, premenstrual syndrome, and chronic fatigue, a 500 to 1,000 mg dose before each of three meals is recommended.
• For stress, 1,500 mg/day is recommended.
• For low sex drive, Parkinson's disease, drug detoxification, and weight loss, 1 to 2 g/day in divided doses is recommended.
• It appears that up to 12 g/day of tyrosine can be ingested safely. However, high-dose therapy should be monitored by a health care provider.

INTERACTIONS

Amphetamine; Ephedrine; Phenylpropanolamine
L-tyrosine (200 and 400 mg/kg) significantly potentiated the anorexigenic effects of phenylpropanolamine (5, 10, or 20 mg/kg), ephedrine (5, 10, or 20 mg/kg), and amphetamine (0.75, 1.25, or 1.75 mg/kg) in a dose-dependent manner in rats (Hull and Maher 1990). More research is needed to determine whether L-tyrosine supplementation would produce similar results in humans.

Levodopa
Levodopa (L-dopa) may decrease tyrosine and tryptophan levels (Riederer 1980). However, administering L-dopa with tyrosine may decrease absorption of the amino acid by competitively inhibiting the transport system (Awad 1984).

Morphine Sulfate
L-tyrosine increased morphine-induced analgesia 154% in mice; only the L-form of tyrosine produced these effects (Hull et al. 1994). Further studies are needed to determine whether L-tyrosine would potentiate the analgesic activity of morphine in humans.