Posted by Jason on 4/7/2020 to Studies and Research
Tyrosine is a popular dietary supplement used to improve alertness, attention and focus.
It produces important brain chemicals that help nerve cells communicate and may even regulate mood (1).
Despite these benefits, supplementing with tyrosine can have side effects and interact with medications.
This article tells you all you need to know about tyrosine, including its benefits, side effects and recommended dosages.
What Is Tyrosine and What Does It Do?
Tyrosine is an amino acid that is naturally produced in the body from another amino acid called phenylalanine.
It’s found in many foods, especially in cheese, where it was first discovered. In fact, “tyros” means “cheese” in Greek (2).
It is also found in chicken, turkey, fish, dairy products and most other high-protein foods (3).
Tyrosine helps make several important substances, including (4):
Dopamine: Dopamine regulates your reward and pleasure centers. 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 or harm (5).
Thyroid hormones: Thyroid hormones are produced by the thyroid gland and primarily responsible for regulating metabolism (6).
Melanin: This pigment gives your skin, hair and eyes their color. Dark-skinned people have more melanin in their skin than light-skinned people (7).
It’s also available as a dietary supplement. You can purchase it alone or blended with other ingredients, such as in a pre-workout supplement.
Supplementing with tyrosine is thought to increase levels of the neurotransmitters dopamine, adrenaline and norepinephrine.
By increasing these neurotransmitters, it may help improve memory and performance in stressful situations (4).
Tyrosine is an amino acid that the body produces from phenylalanine. Supplementing with it is thought to increase important brain chemicals, which affect your mood and stress response.
It May Improve Mental Performance in Stressful Situations
Stress is something that everyone experiences.
This stress can negatively affect your reasoning, memory, attention and knowledge by decreasing neurotransmitters (8,9).
For example, rodents who were exposed to cold (an environmental stressor) had impaired memory due to a decline in neurotransmitters (10,11).
However, when these rodents were given a tyrosine supplement, the decline in neurotransmitters was reversed and their memory was restored.
While rodent data does not necessarily translate to humans, human studies have found similar results.
In one study in 22 women, tyrosine significantly improved working memory during a mentally demanding task, compared to a placebo. Working memory plays an important role in concentration and following instructions (12).
In a similar study, 22 participants were given either a tyrosine supplement or placebo before completing a test used to measure cognitive flexibility. Compared to the placebo, tyrosine was found to improve cognitive flexibility (19).
Cognitive flexibility is the ability to switch between tasks or thoughts. The quicker a person can switch tasks, the greater their cognitive flexibility.
Additionally, supplementing with tyrosine has been shown to benefit those who are sleep deprived. A single dose of it helped people who lost a night’s sleep stay alert for three hours longer than they otherwise would (20).
What's more, two reviews concluded that supplementing with tyrosine can reverse mental decline and improve cognition in short-term, stressful or mentally demanding situations (21,22).
And while tyrosine may provide cognitive benefits, no evidence has suggested that it enhances physical performance in humans (23,24,25).
Lastly, no research suggests that supplementing with tyrosine in the absence of a stressor can improve mental performance. In other words, it won’t increase your brainpower.
Studies show that tyrosine can help maintain your mental capacity when taken before a stressful activity. However, there is no evidence that supplementing with it can improve your memory.
It Might Help Those With Phenylketonuria
Phenylketonuria (PKU) is a rare genetic condition caused by a defect in the gene that helps create the enzyme phenylalanine hydroxylase (26).
Your body uses this enzyme to convert phenylalanine into tyrosine, which is used to create neurotransmitters (27).
However, without this enzyme, your body cannot break down phenylalanine, causing it to build up in the body.
The primary way to treat PKU is to follow a special diet that limits foods containing phenylalanine (28).
However, because tyrosine is made from phenylalanine, people with PKU can become deficient in tyrosine, which can contribute to behavioral problems (29).
Supplementing with tyrosine may be a viable option for alleviating these symptoms, but the evidence is mixed.
In one review, researchers investigated the effects of tyrosine supplementation alongside or in place of a phenylalanine-restricted diet on intelligence, growth, nutritional status, mortality rates and quality of life (30).
The researchers analyzed two studies including 47 people but found no difference between supplementing with tyrosine and a placebo.
A review of three studies including 56 people also found no significant differences between supplementing with tyrosine and a placebo on the outcomes measured (31).
The researchers concluded that no recommendations could be made about whether tyrosine supplements are effective for the treatment of PKU.
PKU is a serious condition that may cause tyrosine deficiency. More studies are needed before recommendations can be made about treating it with tyrosine supplements.
Evidence Regarding Its Effects on Depression Is Mixed
Tyrosine has also been said to help with depression.
Depression is thought to occur when the neurotransmitters in your brain become unbalanced. Antidepressants are commonly prescribed to help realign and balance them (32).
Because tyrosine can increase the production of neurotransmitters, it’s claimed to act as an antidepressant (33).
However, early research doesn’t support this claim.
In one study, 65 people with depression received either 100 mg/kg of tyrosine, 2.5 mg/kg of a common antidepressant or a placebo each day for four weeks. Tyrosine was found to have no antidepressant effects (34).
Depression is a complex and varied disorder. This is likely why a food supplement like tyrosine is ineffective at combating its symptoms.
Nevertheless, depressed individuals with low levels of dopamine, adrenaline or noradrenaline may benefit from supplementing with tyrosine.
In fact, one study among individuals with dopamine-deficient depression noted that tyrosine provided clinically significant benefits (35).
Dopamine-dependent depression is characterized by low energy and a lack of motivation (36).
Until more research is available, the current evidence does not support supplementing with tyrosine to treat symptoms of depression (37).
Tyrosine can be converted into neurotransmitters that affect mood. However, research doesn’t support supplementing with it to combat symptoms of depression.
Side Effects of Tyrosine
Tyrosine is “generally recognized as safe” (GRAS) by the Food and Drug Administration (38).
It has been supplemented safely at a dose of 68 mg per pound (150 mg per kg) of body weight per day for up to three months (39,40,41).
While tyrosine is safe for most people, it can cause side effects and interact with medications.
Monoamine Oxidase Inhibitors (MAOIs)
Tyramine is an amino acid that helps regulate blood pressure and is produced by the breakdown of tyrosine.
Tyramine accumulates in foods when tyrosine and phenylalanine are converted to tyramine by an enzyme in microorganisms (42).
Cheeses like cheddar and blue cheese, cured or smoked meats, soy products and beer contain high levels of tyramine (43).
Antidepressant medications known as monoamine oxidase inhibitors (MAOIs) block the enzyme monoamine oxidase, which breaks down excess tyramine in the body (44,45,46).
Combining MAOIs with high-tyramine foods can increase blood pressure to a dangerous level.
However, it is unknown if supplementing with tyrosine may lead to a buildup of tyramine in the body, so caution is necessary for those taking MAOIs (47,48).
The thyroid hormones triiodothyronine (T3) and thyroxine (T4) help regulate growth and metabolism in the body.
It’s important that T3 and T4 levels are neither too high nor too low.
Supplementing with tyrosine may influence these hormones (49).
This is because tyrosine is a building block for the thyroid hormones, so supplementing with it might raise their levels too high.
Therefore, people who are taking thyroid medications or have an overactive thyroid should be cautious when supplementing with tyrosine.
Levodopa (L-dopa) is a medication commonly used to treat Parkinson's disease (50).
In the body, L-dopa and tyrosine compete for absorption in the small intestine, which can interfere with the drug’s effectiveness (51).
Thus, doses of these two drugs should be separated by several hours to avoid this.
Interestingly, tyrosine is being investigated for alleviating some of the symptoms associated with cognitive decline in older adults (52,53).
Tyrosine is safe for the majority of people. However, it may interact with certain medications.
How to Supplement With Tyrosine
As a supplement, tyrosine is available as a free-form amino acid or N-acetyl L-tyrosine (NALT).
NALT is more water-soluble than its free-form counterpart, but it has a low conversion rate to tyrosine in the body (54,55).
This means that you would need a larger dose of NALT than tyrosine to get the same effect, making the free-form the preferred choice.
Tyrosine is commonly taken in doses of 500–2,000 mg 30–60 minutes before exercise, even though its benefits on exercise performance remains inconclusive (56,57).
It does seem to be effective for preserving mental performance during physically stressful situations or periods of sleep deprivation when taken in doses ranging from 45–68 mg per pound (100–150 mg per kg) of body weight.
This would be 7–10 grams for a 150-pound (68.2-kg) person.
These higher doses may cause gastrointestinal upset and be split into two separate doses, taken 30 and 60 minutes prior to a stressful event.
Tyrosine as a free-form amino acid is the best form of the supplement. Its greatest anti-stress effects have been observed when it’s taken in doses of 45-68 mg per pound (100–150 mg per kg) of body weight about 60 minutes before a stressful event.
The Bottom Line
Tyrosine is a popular dietary supplement used for a variety of reasons.
In the body, it’s used to make neurotransmitters, which tend to decrease under periods of stressful or mentally demanding situations.
There is good evidence that supplementing with tyrosine replenishes these important neurotransmitters and improves mental function, compared to a placebo.
Supplementing with it has been shown to be safe, even in high doses, but has the potential to interact with certain medications, warranting caution.
While tyrosine has many benefits, their significance remains unclear until more evidence is available.