L-Tyrosine: Benefits, Side Effects, And Dosages Guide May 16, 2016


Tyrosine is an amino acid required for brain function. It’s also heavily involved in the synthesis or production of norepinephrine and dopamine. Both of these important neurotransmitters are manufactured in the brain and the adrenal medulla. Tyrosine is an amino acid manufactured in the body through phenylalanine, another amino acid. Tyrosine is vital in the manufacture of neurotransmitters or brain chemicals that transmit signals.

Also known by its full name tyrosine hydroxylase or TH, tyrosine hydroxylase has a huge impact on movement as well as numerous metabolic processes and functions. It acts as a precursor of adrenaline (epinephrine) as well as the aforementioned neurotransmitters, specifically norepinephrine and dopamine, both which have a huge impact on not only mood and behaviors, but are important in stimulating functions in the nervous system as well as metabolic processes.

Tyrosine is a nonessential amino acid. A nonessential amino acid is defined as one that the body can make itself, but only when the necessary components for its construction are available. One major and necessary component for the manufacture of tyrosine is nitrogen, which forms the backbone fragment of amine groups of the amino acids. Nonessential amino acids are often derived from carbohydrates or fats.

The body can’t make all amino acids, which are known as essential amino acids, and hence, they must be obtained from our diet. It sounds backwards, but it’s important to differentiate and understand the difference between essential and nonessential amino acids.

Essential amino acids must be obtained from dietary nutrients. These amino acids include:

  • Histidine
  • Isoleucine
  • Leucine
  • Lysine
  • Methionine
  • Phenylalanine
  • Threonine
  • Tryptophan
  • Valine

The nonessential amino acids produced by the body include:

  • Alanine
  • Arginine
  • Asparagine
  • Aspartic acid
  • Cysteine
  • Glutamic acid
  • Glutamine
  • Glycine
  • Proline
  • Serine
  • Tyrosine

Amino acids are the building blocks of protein synthesis. Protein cannot be developed without amino acids providing the foundation for its construction. Every cell in the body requires protein for life. Amino acids are compounds with an amine group at one end, and an acid group at the other, each with a distinctive side chain (1).

During protein synthesis, the cells assemble amino acids into proteins. However, this process isn’t exactly the same with everyone. Minute differences are found in the ways in which a body manufactures proteins. The instructions for protein manufacture are transmitted in genetic information that is received at conception (2).

Peptide bonds connect one amino acid to another. They all have the same, relatively simply constructed chemical backbone with an amine group or nitrogen containing part at one end and an acid group at the other. The difference between any number of amino acids is based on varying structures of the chemical side chains that are attached to that backbone. Approximately 20 amino acids with different side chains are utilized in making up most of the proteins found in living tissues (3).

Side chains can vary in complexity. Some contain a single hydrogen atom such as glycine while others contain complex structures such as phenylalanine.

The composition, size, and shape of the structures can also differ in their electrical charge. Some side chains are positive, while others are negative, and a few others have no electrical charge. It’s the side chain of an amino acid that helps to determine the behaviors and shape of large protein molecules.

Things To Know About Tyrosine

  • Tyrosine is classified as a nonessential amino acid. The body makes tyrosine from phenylalanine, another amino acid. Tyrosine is an important component in the production of brain chemicals called neurotransmitters, which not only influence mood, but support communication between nerve cells. Tyrosine also has an influence on the manufacture and secretion of hormones from the adrenal, pituitary, and thyroid glands, and is a vital component in the structure of most proteins found in the body.
  • If the body cannot utilize phenylalanine, one of the amino acids from which tyrosine is created, a condition known as phenylketonuria or PKU may occur. This can cause a number of mental disabilities and brain damage for some.
  • Tyrosine also has an influence on the stress response to neurotransmitters norepinephrine and epinephrine (adrenaline). Some studies have attempted to analyze whether that stress contributes to deficiencies of tyrosine. Such small studies using humans and animals have suggested that tyrosine supplementation may reduce lack of focus caused by psychological stress, but additional research in this area is required.
  • Tyrosine is available in a number of dietary sources including but not limited to:
  • Soy products
  • Peanuts
  • Avocados
  • Almonds
  • Bananas
  • Lima beans
  • Mustard greens
  • Spinach
  • Dairy (milk, cheese, cottage cheese, yogurt)
  • Poultry (chicken and turkey)
  • Seeds (sesame seeds and pumpkin seeds)

Chemical Structure


It’s also known by a number of synonyms:

  • (-)-alpha-amino-P-Hydroxyhydrocinnamic acid
  • (-)-ɑ-amino-p-hydroxyhydrocinnamic acid
  • (2S)-2-amino-3-(4-hydroxyphenyl)propanoic acid
  • (S)-(-)Tyrosine
  • (S)-2-Amino-3-(p-hydroxyphenyl)propionic acid
  • (S)-3-(p-Hydroxyphenyl)alanine
  • (S)-alpha-amino-4-hydroxybenzenepropanoic acid
  • 4-hydroxy-L-phenylalanine
  • L-Tyrosin
  • L-Tyrosine
  • Tyr
  • Y

It belongs to the class of Phenylpropanoic acids and the Super Class of phenylpropanoids and polyketides, with a molecular framework of aromatic homomonocyclic compounds.

Mechanism Of Action

The main mechanism of action of tyrosine is its ability to affect mood and focus. It’s mainly used as an antidepressant, though with mixed results. It’s noted to be vital in the production of enzymes and muscle tissues in addition to proteins. It also has an important role in the thyroxin (thyroid hormone) production.

It’s actually produced in the cells through the hydroxylation of the essential amino acid phenylalanine. Roughly half of the phenylalanine consumed by the body is used in the construction of tyrosine, though if a person’s diet is rich in tyrosine, requirements for phenylalanine may be reduced by approximately half (4).

In regard to its efficacy as an anti-depressant, it acts as a precursor in the function of L-tyrosine in regard to neurotransmitter synthesis of dopamine and norepinephrine. It is believed that high levels of dopamine and norepinephrine in the brain are associated with antidepressant effects.

Tyrosine is absorbed in the small intestine and is dependent on sodium transportation processes. It is metabolized in the liver and initiates a number of biochemical reactions, including synthesis of proteins and other oxidative and catabolic reactions. L-tyrosine not metabolized by the liver is circulated systemically to a number of tissues in the body. In metabolic pathways, it has been noted in:

  • Metabolism of tyrosine
  • Biosynthesis of catecholamine
  • Synthesis of thyroid hormone
  • Metabolism of phenylalanine

Tyrosine has been linked to a number of disease processes such as:

  • Phenylketonuria
  • Transient tyrosinemia in newborns
  • Richner-Hanhart syndrome
  • TYRO3
  • Tyrosine hydroxylase deficiency
  • Alkaptonuria
  • Hawkinsinuria
  • Dopamine-beta-hydroxylase deficiency
  • Monoamine oxidase-a deficiency (MAO-A)

Tyrosine functions by attaching to the iodine. This process is involved in the formation of active thyroid hormones. Low levels of tyrosine have therefore been linked to hypothyroidism or decreased thyroid levels in the body. A number of additional symptoms have been linked to deficiencies of tyrosine and include:

  • Restless leg syndrome
  • Decreased blood pressure

Low body temperature, most noted by chronic cold hands and feet, has also been noted.

Symptoms Of Tyrosine Deficiency

Lack of tyrosine can result in deficiencies of norepinephrine in certain locations of the brain, which can have an impact on mood and attitude. This deficiency is most noted in mood disorders like depression. Stress can also have an impact on tyrosine in its ability to function properly.

While it is not common to be deficient in tyrosine, individuals diagnosed with low body temperatures, an underactive thyroid, and low blood pressure may have lower than normal levels or actual deficiencies in tyrosine.

A deficiency of tyrosine hydroxylase can affect movement or contribute to movement disorders noted by their involuntary muscle contractions. Involuntary muscle contractions, known as dystonia, cause unusual or abnormal body posture as well as repetitive, often slow movements, often noted in tremors (5). Individuals may experience mild to severe symptoms. A mild form of tyrosine hydroxylase deficiencies is called TH-deficient dopamine-responsive dystonia or DRD. In most cases, the symptoms are noticed during childhood.

Some of the most obvious symptoms of such a deficiency in children are the unusual placement of a limb or lack of coordination. Another symptom (mild form) is postural tremors, such as a visible shaking or trembling when in a still or static position. Some children may exhibit rolling eye movements, known as involuntary-upward-rolling movements. Left untreated, these movement disorders may increase in severity over time. Medical treatment will diminish these symptoms.

More severe forms of tyrosine hydroxylase deficiencies can occur in children with symptoms that are similar in nature to those associated with Parkinson’s disease. In fact, a severe form of TH deficiency is given the name Infantile Parkinsonism or may also be categorized as Progressive Infantile Encephalopathy. In most cases, these more severe forms of the deficiency appear shortly after birth and can be more challenging to treat.

Some of the major symptoms in babies diagnosed with severe TH deficiencies may include:

  • Delayed motor skills (unsupported sitting, reaching for things)
  • Obvious stiff movements of the arms and legs
  • Untypical body positioning
  • Ptosis (drooping eyelids)
  • The aforementioned involuntary eye movements (typically with the eyeball/s rolling in an upward direction)

Deficiencies in tyrosine may also contribute to a number of issues with the autonomic nervous system, which is responsible for controlling functions in the body over which a person has no control over – digestion, breathing rate, heart rate, and so forth. Other symptoms of such a deficiency may include:

  • Constipation
  • Gastroesophageal reflux
  • Difficulty in maintaining a static body temperature
  • Difficulty in maintaining and regulating blood glucose levels (blood sugar)
  • Difficulty in maintaining a static and stable blood pressure

Psychologically, a person diagnosed with Infantile Parkinsonism may have a number of intellectual difficulties and disabilities. These include:

  • Difficulty in speaking
  • ADD (Attention Deficit Disorder)
  • Depression
  • Increased anxiety
  • Obsessive-compulsive behaviors

Though extremely rare, severe forms of tyrosine hydroxylase deficiencies resulting in progressive infantile and encephalopathy are often diagnosed due to structural abnormalities that cause profound physical deformities, a number of intellectual disabilities, and brain dysfunction.

About Tyrosine Supplements

Tyrosine supplements are denoted with an “L” in front of the name. This letter is commonly found when associated with a number of other amino acids. It basically means that the amino acid (in this context, tyrosine) is in a free-form, or that the amino acid is solitary and not attached to another amino acid.

Tyrosine supplements are used in a number of ways, including for its potential to increase attention and focus, as well as enhanced exercise performance. However, tyrosine used for exercise benefits lacks scientific data to rate it as effective. For example, it has not been scientifically verified to improve endurance or stamina.

In regard to tyrosine and exercise, a 2002 study concluded that tyrosine did not have an influence on heart rate, oxygen update, or exertion rate for cyclists involved in a small study group. The nine cyclists involved in the study were tested for approximately 90 minutes at 70% peak oxygen update under four conditions, both with and without supplementation with carbohydrates (6).

There is a lack of studies in this area, although some small animal studies (rat) have noted that higher doses of ɑ-methyl-p-tyrosine did show some improvement in exercise performance, which also existed with the elevated level of dopamine concentration inside the brain. In this regard, at least during exercise, tyrosine may decrease sensations or feelings of fatigue, which, in turn, can be construed as improving physical performance.

How Is It Used?

Tyrosine supplements (L-Tyrosine) have been used for years to reduce stress and anxiety. Some research has suggested that L-Tyrosine supplements may be beneficial in battling chronic fatigue as well as narcolepsy. It has also been used by consumers to relieve depression, anxiety, headaches, and allergies. Some use it to boost libido, and others believe it may be beneficial in improving mood in regard to symptoms associated with drug withdrawal (7).

Some studies have been conducted in the potential of L-Tyrosine to help relieve symptoms of Parkinson’s disease (8).

Tyrosine can act as a mood elevator. Studies have noted that a lack of tyrosine can lead to deficiencies of brain-produced norepinephrine that can contribute to depressive states.

Tyrosine also behaves as an antioxidant (mild). It has also been researched as an appetite suppressant, and in weight loss, with regard to the reduction of body fat. There is a lack of studies in this area, and further research is required in large, controlled study groups to determine its efficacy.

Tyrosine has also been noted as a component of involvement in adrenal, pituitary, and thyroid gland functions. It’s also involved in the metabolism of phenylalanine, which, as previously mentioned, is required for the synthesis of tyrosine in the body.

Tyrosine Supplement Benefits

1. L-Tyrosine For Anxiety/Stress

L-Tyrosine may be effective in battling the effects of stress and anxiety on the body. While the majority of herbal and natural remedies, compounds, and tinctures sold over the counter without a prescription are marketed to counteract stress affects, most offer little efficacy. The same goes for scientific research regarding such claims.

The same cannot be said of Tyrosine. According to the Journal of Psychiatry & Neuroscience, tyrosine is classified as a catecholamine precursor, meaning that it has an effect on and the potential to alter the availability of L-Tyrosine when it comes to brain functions, mainly in influencing production of norepinephrine and dopamine in animal research that may be translated into human efficacy (9). A number of studies have been performed about the effect of L-Tyrosine and human stress responses.

With regard to emotional and physical stress, L-Tyrosine may have a positive effect in reducing the decline in cognitive function. Dosage studies averaged approximately 20 mg, which is well over the normal dietary intake for daily ingestion. One study involved military combat training, where soldiers were given 2 g daily for five days (10). Results? Improved cognitive function when compared to the placebo effect.

In a longer-term study, 2.5 g of L-Tyrosine given three times daily had neither beneficial nor adverse effects when given to individuals diagnosed with mild hypertension for two weeks (11). However, this particular study was limited to the effect of L-Tyrosine on blood pressure and heart rate.

It should be noted that these studies involving L-Tyrosine do not show much efficacy in reducing stress, but merely the impact that stress may have on cognitive function, alertness, and focus.

2. L-Tyrosine For Weight Control

When combined with a reduced calorie diet and increased levels of exercise, tyrosine supplementation, especially when combined with caffeine, green tea, and calcium may aid in a slight reduction in body fat mass in overweight individuals. One study involving rats explored the possibility that L-Tyrosine could have an influence on hunger hormones ghrelin and leptin, as well as an effect on the hypothalamus with regard to weight loss efforts (12).

3. L-Tyrosine For ADHD

Extended scientific studies and double-blind, placebo-controlled clinical trials regarding the efficacy of tyrosine for mental performance, focus, or attention are also lacking. Some research has determined that the supplement taken two hours before testing does not significantly improve reactions to visual or aural stimulus in healthy individuals, although some studies have shown that tyrosine can reduce the lack of focus or attention to detail for those dealing with stressful situations (13).

The same goes for tyrosine supplements for improved mental performance or enhanced memory. However, taking tyrosine supplements for improving a sense of alertness or focus following lack of sleep may be beneficial for some (14).

For example, consuming the supplement may help individuals maintain focus and alertness for approximately three hours longer than their peers. There is some indication in early research at the tyrosine may improve reasoning skills as well as memory and attention to detail in those who are dealing with sleep deprivation (15). (It should be noted that most of these studies have been conducted on military personnel.)

The bottom line is that few studies have determined the efficacy of tyrosine for beneficial and effective use other than for mental focus following or during stressful situations. That goes for weight loss, substance abuse, degenerative mental diseases such as Alzheimer’s or dementia. No studies have determined that Tyrosine in supplement form aids or improves symptoms of erectile dysfunction, chronic fatigue syndrome, or Parkinson’s disease.

Dosage Guidelines For Tyrosine Supplements

L-Tyrosine should be taken either with a meal high in carbohydrates or at bedtime so that it does not interfere or compete with the absorption of other amino acids. Because it can act as a stimulant, however, it is recommended that it be taken in the morning, with food.

Tyrosine supplements are found in a number of dietary supplement options in tablet or capsule form. Others recommend tyrosine supplements be taken approximately 30 minutes prior to meals, divided into three doses (morning, afternoon, evening). Taking a number of vitamins and minerals such as vitamin B6, and vitamin B9, and copper may help the body convert tyrosine into components important for brain function.

What About Tyrosine Side Effects?

Any supplement, and that goes for tyrosine, does have the potential to cause side effects or interact with certain drugs come either prescription or over-the-counter. Tyrosine supplements may interact with:

  • MAOIs – monoamine oxidase inhibitors found in antidepressant medications including Marplan (isocarboxazid), Nardil (phenelzine), Parnate (tranylcypromine), and Selegiline. The use of tyrosine in combination within a MAOI may cause blood pressure to increase quite drastically in individuals taking prescription antidepressant drugs (16). The increased and very rapid onset of high blood pressure is noted as a hypertensive crisis that increases the risk of heart attack or stroke.
  • L-dopa (Levodopa) due to the fact that levodopa, often prescribed in the treatment of Parkinson’s disease, may interfere with tyrosine absorption.
  • Thyroid hormone drugs. Because tyrosine is known as a precursor of thyroid hormone, it may increase levels beyond normal when combined with synthetic thyroid hormone drugs.

It is recommended that any individual taking medications (prescription or over-the-counter) to treat any medical condition must discuss the use of tyrosine supplementation with a doctor or pharmacist prior to use. The bottom line is that studies reporting the exact benefits or effects of tyrosine on numerous aspects of health and wellness are lacking, though definite benefits in connection with focus and attention to detail can be enhanced when the tyrosine levels rise during stress or fatigue states.