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Tyrosine · 120 capsules

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PEAK

Amino acid and starting point for the synthesis of all catecholamines and thyroid hormones 500 mg L-tyrosine per capsule Vitamin B complex Ideal i...
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L-Tyrosine · 100 capsules

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Biotech USA

Functional amino acid product in capsule form with added iodine Tyrosine can be produced by the body from phenylalanine Tyrosine occurs naturally ...
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Tyrosine is an amino acid that is a popular supplement for improving alertness and concentration. Tyrosine is needed for the production of important brain chemicals that help nerve cells communicate and may even regulate mood (1). Despite these benefits, tyrosine supplementation can also have side effects and interact with certain medications. Tyrosine is conditionally essential. It is formed from phenylalanine and is only essential if this cannot be formed sufficiently. Phenylalanine and, depending on it, tyrosine contribute to the synthesis of important endogenous proteins. These include, for example, insulin, papain and melanin as well as the thyroid hormone thyroxine.

What is tyrosine and what does it do?

Tyrosine is an amino acid that is naturally produced in the body from the amino acid phenylalanine. Tyrosine is also found in many foods including cheese, where it was first discovered. In fact, 'tyros' means 'cheese' in Greek (2). Tyrosine is also found in poultry, meat, fish, dairy products and most other protein-rich foods (3).

Tyrosine is used to produce several important substances, including the following (4):

Dopamine: dopamine regulates the centers in the brain responsible for reward and pleasure. This important brain chemical is also important for memory and motor skills (5).
Adrenaline and noradrenaline: These hormones are responsible for the fight or flight response to stressful situations. They prepare the body to fight or flee from a perceived attack (5).
Thyroid hormones: Thyroid hormones are produced by the thyroid gland and are primarily responsible for regulating metabolism (6).
Melanin: This pigment gives skin, hair and eyes their color. Dark-skinned people have more melanin in their skin than light-skinned people (7).

Tyrosine is also available as a dietary supplement. Some products contain pure tyrosine, while other products, such as pre-workout boosters, contain tyrosine in combination with other ingredients. Tyrosine supplementation is believed to increase levels of the neurotransmitters dopamine, adrenaline and norepinephrine. By increasing the levels of these neurotransmitters, it may help to improve memory and performance in stressful situations (4).

What are the possible benefits of tyrosine supplementation?

Tyrosine could improve mental performance in stressful situations

Stress is something that everyone faces. This stress can impair judgment, memory, attention and knowledge by reducing neurotransmitter levels (8, 9). For example, in rodents exposed to cold (an environmental stressor), reduced memory performance was observed due to a decrease in the amount of neurotransmitters (10, 11). However, when these rodents were given a tyrosine supplement, the decrease in neurotransmitters was reversed and their memory performance was restored. Although data obtained in rodents is not necessarily transferable to humans, human studies have produced similar results. In a study conducted with 22 women as subjects, tyrosine improved working memory in mentally demanding tasks compared to a placebo. Working memory plays an important role in concentration and following instructions (12).

In a similar study, 22 subjects were given either a tyrosine supplement or a placebo before taking part in a test to measure cognitive flexibility. Tyrosine was found to improve cognitive flexibility compared to the placebo (13). Cognitive flexibility is the ability to switch back and forth between tasks and thoughts. The faster a person can switch between tasks, the greater their cognitive flexibility. In addition to this, tyrosine supplementation has been shown to help people who are sleep deprived. A single dose of tyrosine helped people who had not slept for a night stay alert for three hours longer than they would have without tyrosine (14). In addition, two study reviews concluded that tyrosine supplementation during short, stressful or mentally demanding situations can reverse a decline in mental ability and improve alertness (15, 16).

However, although tyrosine may provide cognitive benefits, there is no research showing that tyrosine can enhance physical performance in humans (16, 17, 18). Lastly, it should be noted that there is no research suggesting that tyrosine can improve mental performance in the absence of stressors. In other words, tyrosine will not enhance brain performance.

Summary: Studies show that tyrosine may help maintain mental capacity when taken before stressful activities. However, there is no evidence that tyrosine supplementation can increase memory performance.

Tyrosine could help people with phenylketonuria

Phenylketonuria (PKU) is a rare genetic disorder caused by a defect in the genes that help produce the enzyme phenylalanine hydroxylase (19). The body uses this enzyme to convert phenylalanine into tyrosine, which is used to make neurotransmitters (4). Without this enzyme, the body cannot break down phenylalanine, leading to an accumulation of this amino acid in the body. The primary way to treat phenylketonuria is to follow a special diet that limits the consumption of foods that contain phenylalanine (20).

Since tyrosine is made from phenylalanine, people suffering from phenylketonuria can develop a tyrosine deficiency, which can contribute to behavioral disorders (21). Tyrosine supplementation may be a viable option to alleviate these symptoms, although the scientific data is mixed. In a study review, researchers examined the effects of tyrosine supplementation in combination with or as a replacement for a phenylalanine-restricted diet on intelligence, growth, nutritional status, mortality and quality of life (22). The scientists analyzed two studies with 47 subjects, but could not find any difference between supplementation with tyrosine and a placebo.

Another review of three studies with 56 subjects also found no significant differences between tyrosine supplementation and a placebo in terms of the outcomes measured (23). The researchers concluded that no recommendations can be made as to whether tyrosine supplements could be effective in the treatment of phenylketonuria.

Summary: Phenylketonuria is a serious condition that can cause tyrosine deficiency. Further studies are needed before recommendations regarding treatment with tyrosine supplements can be made.

Studies on the effects of tyrosine supplementation on depression are mixed

Tyrosine is said to help with depression. Depression can be caused by an imbalance of neurotransmitters in the brain. To treat depression, antidepressants are usually prescribed to help restore the balance of these neurotransmitters (24). Since tyrosine can increase the production of neurotransmitters, it is claimed that it can act as an antidepressant (25). However, initial studies do not support this claim. In one study, 65 subjects with depression were given either 100 mg of tyrosine per kilogram of body weight or an antidepressant or a placebo for four weeks. It was found that tyrosine had no antidepressant effect (26).

Depression is a complex and variable disorder. This is probably the reason why a dietary supplement such as tyrosine is not effective in combating symptoms of depression. Nevertheless, depressed individuals with low levels of the neurotransmitters dopamine, adrenaline or noradrenaline may benefit from tyrosine supplementation. A study of subjects suffering from depression caused by dopamine deficiency found that tyrosine had clinically significant benefits (27). Dopamine-dependent depression is characterized by low energy levels and a lack of motivation (27). Until more research is available, the currently available data do not support an effect of tyrosine in the treatment of depression (25).

Summary: Tyrosine can be converted into neurotransmitters that affect mood. Scientific research does not support tyrosine supplementation for the treatment of symptoms of depression.

Side effects of tyrosine

Tyrosine is generally considered safe and harmless (28). Doses of 150 mg per kilogram of body weight over a period of up to three months have been shown to be safe (15, 29, 30). However, even though tyrosine is safe for most people, it may have side effects or interact with certain medications.

Monoamine oxidase inhibitors

Tyramine is an amino acid that helps regulate blood pressure and is produced when tyrosine is broken down. Tyramine accumulates in foods when tyrosine and phenylalanine are converted to tyramine by an enzyme in microorganisms (31). Cheeses such as cheddar and blue cheese, smoked meats, soy products and beer contain large amounts of tyramine (31). Antidepressants called monoamine oxidase inhibitors block the enzyme monoamine oxidase, which breaks down excess tyramine in the body (2, 32, 33). A combination of monoamine oxidase inhibitors with tyramine-rich foods can increase blood pressure to dangerous levels. However, it is not known whether supplementation with tyrosine can lead to an accumulation of tyramine in the body, which is why caution is advised when combining tyrosine with monoamine oxidase inhibitors (34, 35).

Thyroid hormones

The thyroid hormones triiodothyronine (T3) and thyroxine (T4) help to regulate metabolism in the body. It is important that T3 and T4 levels are neither too high nor too low. Supplementation with tyrosine can affect the levels of these hormones (36). This is because tyrosine is a building block for thyroid hormones, so supplementing with tyrosine could increase the levels of these hormones too much. For this reason, people taking thyroid medication or suffering from an overactive thyroid gland should be careful when supplementing with tyrosine.

Levodopa (L-dopa)

Levodopa (L-dopa) is a drug used to treat Parkinson's disease (37). In the body, L-dopa and tyrosine compete in the small intestine for absorption into the body, which can reduce the effectiveness of this medication (38). For this reason, these two drugs should be taken several hours apart. Interestingly, tyrosine is being studied to alleviate some of the symptoms associated with decline in cognitive function in older adults (38, 39).

How to supplement tyrosine

Tyrosine is available in free form and in the form of N-acetyl L-tyrosine. N-acetyl L-tyrosine is more water soluble than L-tyrosine, but has a low conversion rate to L-tyrosine in the body (40, 41). This means that higher doses of N-acetyl L-tyrosine are required to achieve the same effect as with free L-tyrosine. Tyrosine is usually taken in doses of 500 to 2,000 mg 30 to 60 minutes before exercise, although its effects on exercise performance are unclear (42, 43). However, it appears to be effective in maintaining mental performance during physically stressful situations or periods of sleep deprivation when used in doses of 100 to 150 mg per kilogram of body weight. This would be 7 to 10 grams for a 70 kilogram person. However, doses in this range could cause digestive discomfort and should therefore be divided into two single doses taken 30 and 60 minutes before a stressful event.

Tyrosine-rich foods contain the following per 100 grams

Soybeans 1970 mg
Emmental cheese 1800 mg
Peanuts 1540 mg
Wheat germ 1200 mg
Almonds 1400 mg
Tuna 1050 mg
Beef, fillet 930 mg
Trout, blue 920 mg
Cottage cheese 635 mg
1 medium egg 400 mg

Typical groups for an additional requirement of tyrosine

for acute, chronic stress (infections, trauma, sport, etc.)
D- or DL-phenylalanine for chronic pain
possibly for depression
Tyrosine possibly for alcohol withdrawal
Tyrosine possibly for phenylketonuria (if tyrosine levels are low)
in the case of a general lack of amino acids due to certain diseases
in Parkinson's disease

Conclusion

Tyrosine is a popular dietary supplement that is used for a number of different reasons. It is used in the body to produce neurotransmitters, levels of which tend to decrease during stressful or mentally demanding situations. There is evidence that supplementation with tyrosine may restore levels of these important neurotransmitters to normal levels and thereby improve mental function. Tyrosine supplementation has been shown to be safe even when high doses are used, but caution is advised as tyrosine can interact with certain medications.

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