Tyrosine is a nonessential amino acid the body makes from another amino acid called phenylalanine. It is a building block for several important neurotransmitters, including adrenaline (epinephrine), norepinephrine, serotonin, and dopamine. Neurotransmitters help nerve cells communicate and influence mood.
Tyrosine also helps produce melanin (the pigment responsible for hair and skin color) and helps in the function of organs responsible for making and regulating hormones, including the adrenal, thyroid, and pituitary glands. In order for tyrosine to metabolize into these substances, folic acid, niacin, vitamin C, and copper are needed. Tyrosine is involved in the structure of almost every protein in the body.
Generally tyrosine deficiencies are rare. Low levels of tyrosine can lead to shortages in the norepinephrine and dopamine neurotransmitters that regulate mood. Such shortages may cause Depression and/or low blood pressure, low body temperature and restless leg syndrome. This does not mean that the only possible causes of these symptoms is a shortage of tyrosine... there can be other causes that will not respond to tyrosine supplementation.
Some researchers believe that, under stress, the body may not be able to make enough tyrosine from phenylalanine. Some animal and human studies suggest that tyrosine supplements may help improve memory and performance under psychological stress - more research is needed.
Tyrosine also attaches to iodine atoms to form active thyroid hormones. A deficiency of tyrosine has been associated with hypothyroidism.
Since tyrosine is a precursor to the body's manufacture of thyroid hormone, it may raise levels too high if taken with synthetic thyroid hormones. Patients with hyperthyroidism or Graves disease should avoid tyrosine supplements because it may further increase the levels of thyroid hormone.
Because tyrosine binds unstable molecules that can potentially cause damage to the cells and tissues, it is considered a mild antioxidant. It also acts to suppress the appetite, and helps to reduce body fat. Thus, it may be useful in heavy smokers and in individuals exposed to chemicals and radiation.
Phenylketonuria is a serious medical condition which occurs in people who cannot metabolize the amino acid phenylalanine. It leads to brain damage, including mental retardation. People with PKU must avoid any phenylalanine in their diets. Because tyrosine is made from phenylalanine, people with PKU can be deficient in tyrosine. Tyrosine is used in protein supplements for people with PKU, but most doctors don't recommend more tyrosine supplements. If you have PKU, your doctor will determine if you need more tyrosine and how much.
Tyrosine is found in soy products, chicken, turkey, fish, peanuts, almonds, avocados, bananas, milk, cheese, yogurt, cottage cheese, lima beans, pumpkin seeds, and sesame seeds.
Tyrosine is also available as a dietary supplement, in capsule or tablet form.
Because of the potential for side effects and interactions with medications, you should take dietary supplements only under the supervision of a knowledgeable health care provider.
It is recommended that You take tyrosine supplements at least 30 minutes before meals, divided into three daily doses. Taking vitamins B6, B9 (folate), and copper along with tyrosine helps the body convert tyrosine into important brain chemicals.
Tyrosine can also be produced from phenylalanine by the body.
Some athletes claim that tyrosine helps their performance. However, there is no proof that this claim is true or safe.
Because tyrosine helps the body produce the mood-influencing chemicals serotonin and dopamine, and because people who are depressed often have low levels of tyrosine, researchers have thought that tyrosine might help treat depression. However, studies have shown mixed results.
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.
Supplemental L-tyrosine has been used for stress reductions, and research suggests it may be helpful against chronic fatigue and narcolepsy.
Pediatric - There is no specific dietary recommendation for tyrosine. Talk to your doctor before giving a child any dietary supplement.
Adult - Doses vary. Talk to your nutritionist or doctor about what dose is right for you. The dose most commonly recommended is 500 - 1,000 mg three times per day (before each of the three meals). To treat symptoms of sleep deprivation, 150 mg per kilogram of body weight, per day, has been used.
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. Such high-dose therapy should be closely monitored by a health care provider.
People who have migraine headaches should avoid tyrosine, as it can trigger migraine headaches and gastrointestinal upset.
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.
MAOIs include:
L-tyrosine (200 and 400 mg/kg) significantly increases 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 (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).
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.
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.