Tyrosine (L-Tyrosine) is an amino acid that is a precursor for dopamine, epinephrine, and norepinephrine. Tyrosine supplements are taken as nootropics and adaptogens that can help with performance during times of stress. Many people find that it helps significantly with fatigue from stress. Read this post to learn more about tyrosine, its benefits, and its side effects.

What is Tyrosine (L-Tyrosine)?

Tyrosine is a neutral aromatic amino acid. It is a building block for proteins. It is found in many high-protein foods such as cheese, chicken, and eggs.

In the body, tyrosine is mainly used in the brain as a precursor to a class of neurotransmitters called catecholamines (dopamine, norepinephrine, and epinephrine). These catecholamines are responsible for many different cognitive functions [1].

To become a catecholamine, tyrosine (l-tyrosine) requires two or more transformative steps. Firstly, it must be converted into L-3,4-dihydroxyphenylalanine (L-DOPA). Then, additional enzymes turn the L-DOPA into one of the three catecholamines.

Elevated levels of tyrosine increase the production of these neurotransmitters when our bodies need more of them [1].

However, these situations have to be sufficiently challenging to require the extra release of neurotransmitters and subsequent depletion of these neurotransmitters. To maintain optimal neural performance, tyrosine supplementations prevented the neurotransmitters from depleting [2].

Tyrosine (L-Tyrosine) Benefits

1) Improves Memory Under Stress

Tyrosine supplements restored certain “cognitive resources” used to increase working memory [3].

Working memory is responsible for the continued updating and maintenance of memory [2].

Studies showed that tyrosine only replenished certain cognitive resources when the resources get used up, so only challenging situations that require the use of these cognitive resources see improvement [3].

2) Increase Thyroid Hormone Levels (Release)

Thyroid hormones control energy production in the body, aiding in the repair and renewal of damaged cells while increasing resistance to constant stress [4].

In a bird study, chicks with induced tyrosine deficiencies had much lower levels of T3 and T4, common thyroid hormones, in their blood [5].

Birds that were given only phenylalanine supplements, which is the direct precursor to tyrosine, did not gain as much weight as birds that were given phenylalanine plus tyrosine supplements. This evidences that tyrosine supplementation helped in the growth of the chicks [5].

In rat studies where certain rats were put under constant stress, the stressed rats suffered from reductions in T3 and T4 thyroid hormones [4].

This is due to a decrease in the enzymes thyroid peroxidase and oxidase, which are crucial for thyroid hormone production. Many depressed patients also suffered from hypothyroidism [4].

Supplementation with tyrosine increased levels of the neurotransmitter norepinephrine, which increased thyroid hormone release. The tyrosine-supplemented rats not only gained less weight but also exhibited better cognitive function (as measured in maze tests and distance traveled) [4].

3) May Improve Performance During Stress

Tyrosine is a precursor to norepinephrine. Stress reduces norepinephrine levels in the brain (locus coeruleus, hippocampus, and the hypothalamus) [6].

When rats were subjected to shock, norepinephrine levels dropped heavily. But, when tyrosine was injected into the rats, the norepinephrine levels remained constant. This is most likely caused by the fact that tyrosine enhanced the rate of norepinephrine production during stressful situations [6].

The added tyrosine caused the rats to show no behavioral deficits while rats that did not get the tyrosine supplements did show behavioral changes resulting from stress [6].

It was also hypothesized that tyrosine may improve physical performance only if the exercise being done produces enough cognitive stress and depletes dopamine or norepinephrine levels [2].

4) May Improve Attention and Self-Control

Tyrosine administration could help reduce unwanted tendencies [7].

One study describes these tendencies as inhibitory control. When patients were asked to perform a stop-signal task (where the patient clicks stop when a green arrow turns red), patients with tyrosine injections performed better than those with a placebo [7].

Clinical trials of using tyrosine to try to improve attention deficit disorder symptoms in humans showed some positive results. Of the 12 adults that volunteered for the clinical trials, eight of them showed some form of clinical improvement in two weeks [8].

However, after six weeks, all eight of the patients developed a tolerance to the tyrosine and improvements stalled. Further investigation into how tyrosine may be used to cure attention deficit disorders needs to be done [8].

Impaired neurotransmitter energy production may be a predisposition for attention deficit disorder [2].

Although this only accounts for 5 to 10% of the attention deficit disorder cases, it is more likely that such cases would benefit more from tyrosine supplementation [2].

5) May Boost Mood

Tyrosine was found to help depression in certain patients in some clinical trials. A single case, placebo-controlled, case involving a 30-year old woman suffering from depression showed marked improvement after tyrosine therapy [9].

Placebo treatments immediately showcased a return of depression symptoms. Continued tyrosine therapy brought back a marked improvement [9].

Further trials regarding two other patients with depression also showed improvement regarding symptoms [9].

However, a larger clinical trial of 65 patients did not support that tyrosine can be used as an antidepressant [10].

Possibly, this was because depression is dependent on many factors, not simply a lack of dopamine or norepinephrine. Tyrosine might only help depression patients with low dopamine and norepinephrine levels [10].

Improves Mood During Winter Blues

During stressful situations such as the cold or elevated altitudes, increased tyrosine levels improved mood by lowering the intensities of symptoms from the cold and lowered oxygen levels [11].

In a long-term study, patients in Antarctica were given tyrosine supplements daily over the summer and winter. However, during only stressful conditions in the winter months did the tyrosine supplements help to improve mood (by 47%) [12].

Summer conditions were not harsh enough to elicit a response [12].

6) May Help Parkinson’s Disease

Nine patients who had Parkinson’s disease were treated with tyrosine and probenecid. These patients showed an increase in homovanillic acid in the cerebrospinal fluid. The presence of homovanillic acid, a product of dopamine energy production, correlates to the fact that dopamine is being released in the brain [13].

Because Parkinson’s is strongly linked to the degeneration of neurons that release dopamine, increased levels of homovanillic acid could be good proof that tyrosine may be used to treat the disease [13].

Side Effects

1) May Reduce Energy

Although many users state that tyrosine supplementation has benefited them tremendously, some other users have noticed a constant tired state that follows tyrosine supplementation. People take tyrosine supplements sometimes to help their tiredness, but in some cases, it actually made them more tired [14].

2) May Cause Stiffness in the Shoulders and Neck

One user on tyrosine supplementation noticed stiffness in his/her shoulder and neck area. Other reviewers noticed similar side effects and agreed with that user [15].

3) May Lead to Weight Gain

One user noticed that tyrosine supplementation led to unwanted weight gain. Three other reviewers corroborated this side effect [16].

Drug Interactions

1) Interferes with the Uptake of the Parkinson’s Drug L-dopa into the Brain

Tyrosine supplementation may actually interfere with the treatment of Parkinson’s disease [17].

A common occurrence in the disease is the “on-off” phenomenon where levodopa is not as well absorbed or transported at times [18].

During the “off” times of the disease, the patients are barely able to walk at all or accomplish their everyday tasks, necessitating the need for a constantly “on” treatment [18].

Studies of nine patients showed that when amino acid-rich meals were taken, the levodopa concentrations in the blood decreased by 29% and the absorption was delayed by 34 minutes [18].

This happens due to the competing nature of levodopa and tyrosine into the brain. Higher levels of tyrosine can reduce the transport of levodopa into the brain reducing the effectiveness of the treatment [17].

2) Supplementation with Thyroid Hormone Pills May Lead to Overload of Thyroid Hormones

Tyrosine supplementation leads to an increase in thyroid hormones [4].

If this supplement is taken along with thyroid hormone pills, the body may produce too many of the hormones and cause unwanted side effects. Thyroid hormones control a wide range of bodily processes such as regulating the energy production in the body, aiding in the repair and renewal of damaged cells, and increasing resistance to constant stress, so excessive hormones may damage the body’s ability to perform these tasks [4].

Please consult a professional before taking tyrosine supplements when using other drugs.

Synergies with Other Supplements

Users of tyrosine supplements have also seen major improvements when combined with other supplements. Some users that use tyrosine to fight depression have noticed improvements when using tyrosine supplements along with 5-HTP, a tryptophan supplement. This is because 5-HTP increases serotonin in the brain while the tyrosine increases dopamine and norepinephrine, which all have to do with increasing mood [14].

The user mentions that other antidepressants like Prozac only increase serotonin so tyrosine supplementation can help with increasing the release of other neurotransmitters [19].

Another user suffering from fatigue and low adrenal output also used the tyrosine supplement along with 5-HTP and found similar beneficial effects [14].

Combining the tyrosine supplements with a Super Cortisol supplement from Now Foods has helped another patient suffering from fatigue. The user mentions that energy levels have increased and that brain fog has disappeared after combined usage [14].

However, drug mixing should always be done under the supervision of a doctor. Please consult with your local physician before combining any supplements.

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