L-tyrosine (4-hydroxyphenylalanine) is a nonessential amino acid that the body synthesizes from phenylalanine. This amino acid is necessary for making the brain neurotransmitters dopamine, epinephrine and norepinephrine. Neurotransmitters help nerve cells communicate and influence mood. Tyrosine is made in our bodies and is also found naturally in animal protein and plant protein.
Natural Sources
Tyrosine is found naturally in soy products, fish, turkey, chicken, almonds, peanuts, bananas, avocados, milk, cheese, yogurt, cottage cheese, eggs, lima beans, oats, wheat germ, pumpkin seeds and sesame seeds.
Tyrosine Benefits and Health Effects
Tyrosine is the precursor of the catecholamines; alterations in the availability of L-tyrosine to the brain can influence the synthesis of both dopamine and norepinephrine in experimental animals and presumably in humans. In animals, stress increases the release of catecholamines, which can result in the depletion of their levels, an effect that can be corrected by giving tyrosine. Some studies show that tyrosine supplements boosts mental performance under stress. In a study, tyrosine was given at a dosage of two grams per day for five days during a demanding military combat training course; it improved various aspects of cognitive function relative to placebo. A 2010 study reported in the “Journal of the International Society of Sports Nutrition” found that tyrosine supplement led to significantly greater improvements in focus and alertness after exhaustive exercise. In a study, a protein drink containing 10 g per day of tyrosine was more powerful than a carbohydrate drink for improving mental performance scores in a group of cadets taking a stressful 6-day combat training course. In another clinical trial found that one-time administration of 150 mg of tyrosine per 2.2
pounds of body weight helped prevent a decline in mental performance for approximately 3 hours during a night of sleep deprivation.
In a study, alcoholics treated with tyrosine combined with other supplements had reduced withdrawal symptoms. In this clinical trial, a group of alcoholics were treated with 1.5 g of D,L-phenylalanine, 400 mg of tryptophan, 300 mg of glutamine and 900 mg of L-tyrosine per day, plus a multivitamin-mineral supplement. This supplement regimen led to a important decline in withdrawal symptoms and decreased stress in alcoholics compared to the effects of placebo.
L-tyrosine reduces the symptoms of Parkinson’s disease by increasing the levels of dopamine in the brain. A study reported in 1982 in “Life Sciences” demonstrated that tyrosine may benefit patients with Parkinson’s disease. Scientists administered 100 mg/kg of tyrosine to each of the 23 patients with Parkinson’s disease. Evaluation of tyrosine’s effect in 23 Parkinson’s disease patients showed 100 mg/kg tyrosine daily raised plasma and cerebral spinal fluid tyrosine and homovanillicacid levels, indicating increased catecholamine synthesis and release. In a small study showed that some patients with Parkinson’s disease who supplemented with tyrosine for 3 years had better clinical results and fewer adverse effects than did patients using L-dopa.
Tyrosine Dosage
As reported in the literature, the recommended daily dosage of tyrosine is 100-150 mg/kg body weight. Some health professionals recommends taking tyrosine supplements 30 minutes before meals in three daily doses between 500 to 1,000 mg each. L-Tyrosine may need to be supplemented with its synergistic amino acids including 5-Hydroxytryptophan, L-Phenylalanine, and L-Methionine. Also, vitamin B6, B9, and copper are necessary for conversion of tyrosine into neurotransmitters.
Side Effects
Tyrosine is usually safe with infrequent reports of adverse effects. Occasional nausea,vomiting, diarrhea, or insomnia are reported by those taking higher doses of tyrosine (>150 mg/kg daily). Tyrosine can interact with certain other drugs. Before adding tyrosine supplements to drugs such as Levothroid , levoxyl, unithroid synthroid, or consult with your doctor. Tyrosine may cause a severe increase in blood pressure in people taking antidepressant drugs known as Monoamine Oxidase Inhibitors (MAOIs). Tyrosine should not be taken at the same time as Levodopa (L-dopa). The use of tyrosine with L-dopa may lower the effectiveness of L-dopa because they compete for absorption in the small intestine.
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