什麼是L-酪胺酸?

What is L-tyrosine?

L-tyrosine is an amino acid found in the diet that is metabolized to produce catecholamines such as dopamine (DA) and norepinephrine (NE). L-tyrosine is also used in the production of thyroid hormone. L-Tyrosine is often taken as a supplement to help increase the levels of catecholamines that are consumed during stressful or challenging conditions. It is used as a free form amino acid supplement, often alone or as part of a weight loss or pre-workout supplement.

What are the main benefits of L-Tyrosine?

The primary benefit of L-tyrosine is related to its ability to replenish catecholamine levels in the brain, which can be depleted during stressful conditions. Multiple studies have shown that L-tyrosine helps prevent cognitive decline under stressful, cognitively demanding conditions. Although L-tyrosine supplementation has not been shown to improve memory under resting conditions, L-tyrosine supplementation has been shown to alleviate memory decline under acute stress conditions. Overall, moderate doses of L-tyrosine appear to be safe and well-tolerated, with one 2-week human trial using a dose of 2,500 mg delivered three times daily for two weeks, and another Trials have used single doses up to 150 mg/kg body weight (approximately 10,000 mg for a 68 kg/150 lb individual), with no adverse effects.

What are the main disadvantages of L-tyrosine?

Although L-tyrosine has shown beneficial effects in some studies, its record of efficacy is mixed, with some studies failing to observe positive effects on cognition. This may be explained in part by the fact that L-tyrosine only increases catecholamine synthesis when catecholamine levels are depleted, thus limiting efficacy to sufficiently stressful or challenging conditions. Efficacy may also vary between individuals, as highlighted by one study that found that L-tyrosine's effects on cognitive function become detrimental as we age. People with hyperthyroidism or those taking levodopa or monoamine oxidase inhibitors may also have contraindications to L-tyrosine supplementation. If this happens to you, consult your doctor before supplementing with L-tyrosine.

How does L-tyrosine work?

L-tyrosine is used in the body to produce catecholamines, dopamine (DA), and norepinephrine (NE), which may be depleted under conditions of stress or cognitive challenge. After supplementation, L-tyrosine levels in the blood peak after one to two hours and remain elevated for up to eight hours. L-tyrosine then crosses the blood-brain barrier, is absorbed by brain cells, and is converted into DA in a series of enzymatic reactions. DA can be converted into NE through the action of another enzyme. L-tyrosine's ability to enhance catecholamine synthesis only in actively firing neurons may explain its ability to reverse the effects of neurotransmitter depletion during stress.

Should You Try L-Tyrosine Supplements? Check out its benefits and side effects

With so many different supplements claiming to improve sleep, boost the immune system, and improve heart health (just to name a few), it can be hard to know which ones might work and which ones won't.

L-tyrosine, for example, has gained widespread attention for its ability to help relieve stress and improve memory. But does this non-essential amino acid, also known as tyrosine, really live up to the hype?

As a non-essential amino acid, your body naturally produces L-tyrosine. It is used as a building block of proteins. It is made from an essential amino acid called phenylalanine.

So, what does L-tyrosine do?

In addition to building protein, L-tyrosine helps your body produce enzymes, thyroid hormones, and melanin, and aids in communication between nerve cells.

Although L-tyrosine is produced naturally in the body, you can also get it from certain foods, such as cheese, cured or smoked meats, soy products, avocados, and nuts.

So, do we still need it as a supplement?

L-Tyrosine Benefits

What is L-tyrosine used for? While the benefits of L-tyrosine may help relieve stress and depression, more research is needed to fully understand the role this amino acid plays in our bodies.

May be helpful in stressful situations

Who hasn’t been stressed? When we are stressed, we may have difficulty thinking clearly, retaining information, and concentrating.

Research is investigating whether L-tyrosine can help improve mental performance in stressful situations in humans.

In one example, participants who took a test measuring cognitive flexibility performed better when taking L-tyrosine supplements than when taking a placebo. Another study showed that working memory improved after taking L-tyrosine in people engaged in highly mental tasks.

L-tyrosine has not been shown to improve memory under resting conditions. It has been shown to alleviate memory loss under stressful conditions. The stress factor is the key. If you are stressed, your neurotransmitters are depleted, and therefore, your L-tyrosine levels may be lower.

May help relieve depression

One in six people will be affected by depression in their lifetime. While we don't know exactly why someone experiences depression, one belief is that it has to do with an imbalance in the brain's chemicals and its neurotransmitters like serotonin and dopamine.

L-tyrosine increases neurotransmitters in the brain, making it a possible treatment for depression.

It's important to know that early studies have had mixed results. One study showed that L-tyrosine did not have any antidepressant effects, while another study showed that individuals with low dopamine levels saw significant benefits when supplementing with L-tyrosine.

Until there is more conclusive research, L-tyrosine supplements are not recommended for treating depression.

May help patients with phenylketonuria

Phenylketonuria (PKU) is a rare genetic disorder caused by a defect in the gene that plays a role in producing phenylalanine hydroxylase, an enzyme. This special enzyme is used to make L-tyrosine.

Low levels of L-tyrosine can lead to mental health disorders. Whether L-tyrosine supplementation helps relieve PKU symptoms has yet to be determined, as studies have shown no improvement when taking L-tyrosine supplements.

L-tyrosine side effects

L-tyrosine supplements are considered generally safe by the U.S. Food and Drug Administration (FDA), but they may interact with certain medications, such as:

  • Thyroid hormone.
  • Monoamine oxidase inhibitors (MAOIs).
  • Levodopa (L-dopa).

It's important to remember that supplements are not regulated by the FDA. So make sure you do your homework on the brand to see if there are other additives added.

Is L-Tyrosine Right for You?

Most people will not benefit from taking L-tyrosine supplements. It's best to discuss with your healthcare provider whether taking an L-tyrosine supplement is right for you.

You can find L-tyrosine supplements as part of a sports supplement package. As for how much to take .

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