Tyrosine is a powerful amino acid that is a building block for dopamine, epinephrine, norepinephrine, and thyroid hormones. Tyrosine supplements are nootropics and adaptogens that help with performance during times of stress. Many people find that it even helps significantly with fatigue from stress!!!

1) Tyrosine Replenishes Cognitive Resources Used in Memory

Tyrosine supplements restored certain cognitive resources used to increase working memory. Working memory is responsible for the continued updating and maintenance of memory.

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 an enhancement of the cognitive resources.

2) L-Tyrosine Is a Building Block of Thyroid Hormones

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

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

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. Many depressed patients also suffered from hypothyroidism.

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 had better cognitive function (as measured in maze tests and distance traveled).

3) Tyrosine Increases Dopamine Levels in the Brain

Tyrosine supplementation increased dopamine levels in the striatum of the brain when animals are given treatments that increase dopamine demand.

Tyrosine administration also increased dopamine levels in the extracellular fluid of the brain. However, this effect was short-lived as excessive tyrosine in the brain also slowed down neuronal firing. This, in turn, brought the dopamine levels back to the original levels before tyrosine administration.

4) Tyrosine Helps with Performance During Stress

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

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.

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.

5) Tyrosine May Improve Attention Deficit Disorders

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.

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.

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

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.

6) Tyrosine to Treat Depression

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.

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

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

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

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.

7) Tyrosine for Treatment of 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.

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.

8) Tyrosine Improves Inhibition

Tyrosine supplementation could help reduce unwanted tendencies.

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.

9) Tyrosine 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.

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.