Justus von Liebig discovered tyrosine in 1846. The nonessential amino acid aids in the synthesis of proteins. Together with phenylalanine, the two amino acids form adrenaline or epinephrine. While it is available as a dietary supplement, tyrosine occurs naturally in many foods including eggs, sesame and pumpkin seeds, and cheese. The recommended dietary intake for both tyrosine and its precursor phenylalanine is 15 milligrams per pound of body weight. This is an easy recommendation to fulfill: three ounces of lean beef contains approximately one gram, and an egg white contains about 250 milligrams.
During times of stress, the body releases neurotransmitters called catecholamines, which facilitate nerve cell communication, and noradrenaline, which plays a role in the sympathetic nervous system. This flood of chemicals can cause depletion, affecting function and moods. For example, depletion of these chemicals can lead to muscle stiffness and sleep disturbances. Studies show tyrosine, a precursor to some brain neurotransmitters, can help to protect against the mental fatigue that can come with stressful situations.
There is often a deficit of neurotransmitters such as noradrenaline and dopamine in individuals with ADHD and autism. Both of these chemicals are responsible for maintaining focus and mental acuity. Dopamine is specifically linked to the frontal lobes, which control mood. Tyrosine, in conjunction with key vitamins, improves cognitive skills and emotional expression. This is why doctors recommend protein-rich diets in addition to traditional treatments for these conditions.
Hypothyroidism occurs when the pituitary gland does not produce enough of the thyroid-stimulating hormone TSH, resulting in slow metabolism. While medications can treat this disorder, physicians also recommend high-protein diets that include tyrosine-rich foods. One exception is soy. While rich in tyrosine, it also contains goitrogens that interfere with gland function. Peanuts are also rich in both tyrosine and goitrogens. Rather, doctors may recommend seafood and cheeses such as Swiss and Romano.
Hypertension is one of the most common and manageable noncommunicable diseases that, if left untreated, can lead to serious complications. One clinical trial suggests a high-protein diet could help reduce systolic blood pressure. However, another study provides deeper insight. It seems that among a handful of amino acids tested, tyrosine, at an optimized level of 200 milligrams per kilo, has a significant antihypertensive effect. There are many theories about how this happens, including that tyrosine may prompt the release of catecholamines in the central nervous system that lower arterial pressure.
Tyrosinemia is a genetic disorder that creates a shortage of fumarylacetoacetate hydrolase or FAH, which the body requires to break down tyrosine. People with this condition have a buildup of tyrosine and by-products in their tissues and organs. One type of this disorder, hepatorenal tyrosinemia or type I, affects children within the first few months of life and can lead to liver and kidney failure. Individuals with this condition need to be on a lifelong low-tyrosine and low-phenylalanine diet, in conjunction with medication.
Tyrosinemia type II, Richner Hahart syndrome, and type III are extremely rare forms of this disease. Type II is caused by a deficiency of tyrosine aminotranserase or TAT, and causes skin lesions in the palms and soles, as well as corneal ulcers. Type III is a deficiency of the enzyme 4-hydroxyphenylpyruvate dioxygenase or HPD. Both types may develop in conjunction with intellectual disability, seizures, and some loss of coordination. Diagnosis leads to medication and restricted diets.
Tanning usually involves prolonged sun exposure that can increase the chances of skin cancer and premature aging due to the oxidation process. Melanin, the skin-darkening pigment, is made by melanocytes, and melanogenesis requires oxidization of tyrosine to produce melanin. Rather than excessive exposure to the sun, some doctors suggest supplementing with between 1,000 and 1,500 milligrams of tyrosine daily, in conjunction with other vitamins and regular sunscreen, to achieve a natural tan without dangerous side effects.
Melanoma is a cancerous tumor that can develop on melanin-forming cells anywhere in the body, though it most often affects the skin. A study on mice with pigmented melanoma that were going through chemotherapy showed that reduced tyrosine and phenylalanine levels during this treatment increased melanoma survival rates by as much as 76 percent. This implies that tyrosine may promote pigmented melanoma tumor activity and should be avoided during treatment.
Hyperthyroidism is the overproduction of thyroid hormones, which causes a high metabolic rate, rapid heart rate, high blood pressure, and more. Tyrosine is one component of the main thyroid hormone, thyroxine. People with overactive thyroids who take supplemental tyrosine can further increase their thyroxine levels, possibly triggering arrhythmia or a hypertensive crisis.
Alcohol addiction alters the brain over time and can lead to deficiencies and personality changes. Chronic alcohol overuse alters the activity of neurotransmitters such as serotonin and dopamine, causing behavior disorders and depression. A double-blind research study showed that doses of amino acids, including phenylalanine and tyrosine, reduced withdrawal symptoms and made the alcohol detoxification process less stressful.
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