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 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.

Roles and Functions

In the body, tyrosine is mainly used in the brain as a precursor to a class of neurotransmitters called catecholamines [1]:

These catecholamines are responsible for many different cognitive functions [1].

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

Stress and challenging situations require the extra release of neurotransmitters and their subsequent depletion. Tyrosine supplements prevent the neurotransmitters from depleting and thus maintain optimal brain performance [2].

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) Increases Thyroid Hormones

Thyroid hormones control energy production, repair and renewal of damaged cells, and resistance to 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. This is due to a decrease in the enzymes thyroid peroxidase and oxidase, which are crucial for thyroid hormone production [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 [4].

3) May Improve Performance During Stress

Tyrosine is a precursor to norepinephrine, and stress reduces norepinephrine levels in the brain [6].

When rats were subjected to shock, norepinephrine levels dropped heavily. But, when tyrosine was injected into the rats, the norepinephrine levels remained constant due to enhanced norepinephrine production [6].

The added tyrosine prevented stress-induced behavioral deficits in rats [6].

Tyrosine may also improve physical performance but only if the exercise produces enough cognitive stress to deplete dopamine or norepinephrine levels [2].

4) May Improve Attention and Self-Control

In one study, tyrosine injections reduced uncontrolled emotional responses [7].

A clinical trial of L-tyrosine for attention deficit disorder symptoms in humans showed some positive results. Eight out of 12 adult participants showed some clinical improvement in two weeks [8].

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

Impaired dopamine production may be a predisposition for attention deficit disorder. It accounts for 5 to 10% of the attention deficit disorder cases, and it’s more likely that such cases would benefit from tyrosine supplementation [9].

5) May Boost Mood

In a single placebo-controlled case, a 30-year old woman suffering from depression showed marked improvement after tyrosine therapy [10].

Placebo treatments immediately showcased a return of depression symptoms while continued tyrosine therapy brought back a marked improvement [10].

Further trials with two depressed patients also showed improvement of the symptoms [10].

However, a larger clinical trial of 65 patients failed to verify the antidepressant effects of L-tyrosine [11].

Depression is dependent on many factors, not just a lack of dopamine or norepinephrine. Tyrosine might only help depressed patients with low dopamine and norepinephrine levels [11].

Improves Mood During Winter Blues

During stressful situations such as the cold or elevated altitudes, tyrosine supplementation improved mood by reducing the impact of the cold and lowered oxygen levels [12].

In a long-term study, 85 subjects in Antarctica received tyrosine supplements daily over the summer and winter. Tyrosine supplements improved mood (by 47%) only during stressful conditions in the winter months [13].

6) May Help With Parkinson’s Disease

Nine patients who had Parkinson’s disease were treated with tyrosine and probenecid. These patients showed signs of a boosted dopamine release in the brain [14].

Because Parkinson’s is strongly linked to the degeneration of dopamine neurons, tyrosine may be used to treat the disease [14].

L-Tyrosine Side Effects & Drug Interactions

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 [15].

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 [16].

3) May Lead to Weight Gain

One user noticed that tyrosine supplementation led to unwanted weight gain. Three other reviewers corroborated this side effect [17].

Drug Interactions

1) Interferes With the Uptake of the Parkinson’s Drug L-DOPA into the Brain

A common occurrence in the disease is the “on-off” phenomenon where levodopa is not as well absorbed or transported at times. During the “off” times, the patients are barely able to walk at all or accomplish their everyday tasks [18].

A study of nine patients showed that amino acid-rich meals dropped the levodopa concentrations in the blood by 29% and delayed its absorption by 34 minutes [19].

This happens due to the competition between levodopa and tyrosine for brain transport. Higher levels of tyrosine can hinder the transport of levodopa into the brain, reducing the treatment effectiveness [20].

2) Combination With Thyroid Hormone Pills May Lead to Overload of Thyroid Hormones

Tyrosine supplementation increases thyroid hormones [4].

If this supplement is taken along with thyroid hormone pills, the body may produce too much and cause unwanted side effects. Thyroid hormones control various functions—such as energy production, repair and renewal of damaged cells, and stress resistance—so excessive hormones may hinder the body’s ability to perform these tasks [4].

Please consult a health professional before taking tyrosine supplements.

Using L-Tyrosine

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 combine them with 5-HTP, a tryptophan supplement. This is because 5-HTP increases serotonin in the brain while tyrosine increases dopamine and norepinephrine, which all impact mood.

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

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

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.

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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