L-tyrosine can boost your cognition, mood, and thyroid hormones, especially when you’re under stress. However, it may do the opposite and worsen mental health in some cases. Read on to discover both sides of L-tyrosine supplements and learn how to use them properly.
What is L-Tyrosine?
The “Cheese” Amino Acid
L-tyrosine is a naturally occurring form of tyrosine, an amino acid your body uses to make proteins, neurotransmitters, and other vital compounds .
We don’t depend on food sources of tyrosine since we can make it from another amino acid, phenylalanine; this makes tyrosine a non-essential amino acid. Still, you can ensure its optimal levels by eating a variety of tyrosine-rich foods such as [2, 3]:
- Cheese and dairy
Did you know? Scientists named tyrosine after cheese (Greek: tyros), where they discovered it.
L-tyrosine is a popular nootropic supplement; people use it to boost cognition and alertness under stress. You will find it alone or combined with other ingredients in protein and pre-workout supplements.
- Boosts cognition under stress
- Helps with mood disorders
- May improve attention
- May boost thyroid hormones
- Helps with fibromyalgia
- May cause headache and anxiety
- May worsen cognition in the elderly
- Interacts with L-DOPA and thyroid medications
Roles and Functions
In your body, tyrosine acts as a precursor to neurotransmitters called catecholamines :
As a supplement, L-tyrosine may be beneficial under stressful conditions that deplete your catecholamines.
N-acetyl-L-tyrosine (NALT or NAT) is more water-soluble than L-tyrosine and thus more suitable for intravenous nutrition for people who can’t eat and drink .
As a nutritional supplement, our bodies supposedly use it better than L-tyrosine, but the evidence tells a different story. We metabolize only 25% of NALT into free tyrosine and eliminate 35-38% with the urine [9, 10, 11].
In a study of 13 subjects, N-acetyl-L-tyrosine didn‘t increase tyrosine levels at all .
Thus, L-tyrosine remains a better option for oral supplementation.
1) Boosts Cognition Under Stress
A review of 15 clinical trials investigated the effects of L-tyrosine loading – short bouts of higher doses – on cognition and behavior. This dosing pattern prevented catecholamine depletion and boosted mental function in stressful and demanding situations .
It showed the best results in people exposed to:
- Multitasking and distractions [14, 15, 16]
- Sleep deprivation [17, 18]
- Harsh military training [19, 20]
- Cold weather [21, 22, 23]
Additionally, L-tyrosine may not improve cognitive performance under normal conditions. In older adults, L-tyrosine loading even produced the opposite effects – worsening memory and cognitive function .
2) Helps With Mood Disorders
Imbalances in brain neurotransmitters can lead to depression and other mood disorders. Since tyrosine enables the production of dopamine and noradrenaline, it may act as nutritional mood support .
Some doctors have reported success with L-tyrosine for a couple of patients with depression .
It seems to be beneficial for particular mood disorders such as:
- Depression due to low dopamine 
- Low mood from living in harsh, cold environments [31, 32]
- Depression after childbirth 
However, the above results stem from small clinical trials, some of which lacked placebo controls. A larger trial of 65 patients failed to verify the antidepressant effects of L-tyrosine .
3) May Boost Thyroid Hormones
In 85 volunteers, supplementation with high doses of L-tyrosine (12 g daily) during harsh winter slightly increased T3, the active thyroid hormone. It also greatly reduced TSH, high levels of which are linked with hypothyroidism and stress .
Tyrosine supplementation prevented thyroid hormone drops in mice exposed to chronic stress .
Large, well-designed clinical trials should confirm the benefits of L-tyrosine supplementation for thyroid health.
4) May Help With Attention Disorders
In a clinical trial, L-tyrosine improved attention in eight of 12 participants with attention deficit disorder over two weeks. However, after six weeks, all patients developed a tolerance to the treatment, and their improvement stalled .
L-tyrosine supplementation provided no benefits to 7 children with ADHD .
Impaired production of dopamine and noradrenaline may trigger attention disorders, and such cases would more likely benefit from tyrosine supplementation .
Combination With Adderall
L-tyrosine helps restore catecholamines, and some people combine it with Adderall to lessen the side effects. No studies have verified the safety and efficacy of this combination.
5) Combats Narcolepsy
Patients with narcolepsy struggle to stay awake during the day. They often experience cataplexy (sudden muscle weakness with intact awareness) and sleep paralysis .
In a study of 10 patients, L-tyrosine improved only three of more than 20 tested symptoms. The patients felt less tired and more alert .
A group of doctors managed to handle daytime sleep attacks and cataplexy with L-tyrosine in eight patients. They kept using this approach in other narcolepsy patients after the initial success. The lack of placebo controls doesn’t allow for a definite conclusion .
6) May Relieve Addiction and Substance Withdrawal
Dopamine plays a central role in the brain’s reward pathway. Scientists first thought that it makes certain things (such as food and sex) enjoyable. New research suggests dopamine actually doesn’t make us feel pleasure, it makes us want it. People with addiction may be depleting or over-sensitizing this pathway, which increases their cravings and drug-seeking behavior .
- Anger and hostility
- Suppressed vigor
Tyrosine supplies catecholamines and thyroid hormones, which both enhance metabolism and energy production. For this reason, many people want to know if L-tyrosine can boost weight loss.
No other trials have documented the benefits of L-tyrosine for weight loss.
People with an inborn metabolic disorder – phenylketonuria (PKU) – are unable to break down phenylalanine properly. In turn, the buildup of phenylalanine causes brain damage and cognitive impairment [50, 51, 52].
These patients should follow a special low-protein diet to minimize the intake of phenylalanine. They are at risk of tyrosine deficiency since the body converts phenylalanine into tyrosine.
L-tyrosine supplementation for PKU may sound reasonable, but a Cochrane Database review of six clinical trials failed to confirm its benefits .
L-Tyrosine Side Effects and Precautions
According to the FDA, L-tyrosine is “generally recognized as safe” (GRAS) .
High doses (100-200 mg/kg) caused cognitive decline in older adults .
L-tyrosine competes for brain uptake with L-DOPA, a drug for Parkinson’s disease. Tyrosine supplements and even tyrosine-rich foods may hinder the transport of L-DOPA into the brain; this can lead to variations in the treatment response, known as the “on-off” phenomenon [59, 60].
Patients with Parkinson’s disease are often deficient in tyrosine hydroxylase – an enzyme that converts tyrosine to L-DOPA – which is another limitation for tyrosine supplements .
High doses of L-tyrosine (12 g daily, for 4 months) can increase thyroid hormones. People with an overactive thyroid and those taking thyroid medications may want to avoid it .
L-Tyrosine Dosage & Supplements
Average L-tyrosine dosage for most conditions is 100 mg/kg; that would be around 7 g daily for a 154-lbs (70-kg) person, divided into 2-3 daily doses. It’s a good idea to start with a lower dose and work your way up to an optimal response [13, 24].
For short-term cognitive enhancement, you should take L-tyrosine 30-60 mins before a stressful or challenging task. Benefits for depression, fibromyalgia, and attention disorders usually take 1-4 weeks [13, 30, 45, 38].
Most products contain 500 mg of L-tyrosine per pill. If you need long-term supplementation with higher doses, bulk powders might be a better option.
Users take L-tyrosine to boost their mental clarity, alertness, and focus. A smaller number has reported success with depression, sugar cravings, and alcohol withdrawal.
Combinations with antidepressants and other supplements such as 5-HTP are popular for mood disorders, but you should never combine drugs and supplements before consulting with your doctor.
Other users experienced no benefits for cognition and mental health; some of them even said their mood and focus worsened. The most common side effects are anxiety, headache, and insomnia. Users also suggest starting with lower doses to see how your body will react.
Want More Targeted Ways to Enhance Brain Function and Mood?
If you’re interested in natural and targeted ways of improving your cognitive function, we recommend checking out SelfDecode’s Limitless Mind DNA Protocol. It gives genetic-based diet, lifestyle and supplement tips that can help improve your cognitive function. The recommendations are personalized based on your genes.
Also check out SelfDecode’s Mood DNA Wellness Report. It also gives genetic-based diet, lifestyle and supplement tips that can help improve your mood.
SelfDecode is a sister company of SelfHacked. This post contains sponsored links, which means that we may receive a small percentage of profit from your purchase, while the price remains the same to you. The proceeds from your purchase support our research and work. Thank you for your support.
L-tyrosine is an amino acid that builds proteins, neurotransmitters, and thyroid hormones in your body. Protein-rich foods such as cheese, meat, eggs, and beans are great sources of this amino acid.
Supplementation with L-tyrosine boosts your cognitive performance when you’re under stress. It may also improve mood and attention and help with substance dependence.
L-tyrosine may cause headache, anxiety, and nausea. Pregnant women, children, and people taking L-DOPA or thyroid hormones should avoid it unless prescribed by a doctor.