Short answer. L-tyrosine is an amino acid the body uses to build dopamine and norepinephrine. In a 2015 research review, extra tyrosine helped thinking mainly in short, stressful or demanding moments, not in everyday life (PMID 26424423). Most people already make enough from protein and from the amino acid phenylalanine.
L-tyrosine at a glance
Tyrosine shows up in supplements in a few forms, and on food labels as part of protein. Here is how they compare.
| Form | What it is | What to know |
|---|---|---|
| Free-form L-tyrosine | The amino acid on its own | The form used in most of the human studies below; taken in the morning, away from protein |
| N-acetyl L-tyrosine (NALT) | Tyrosine with an acetyl group attached, which dissolves more easily | More soluble, but the human data suggest the body may use it poorly (see below) |
| L-phenylalanine | The essential amino acid the body converts into tyrosine | Not for anyone told to limit phenylalanine, including people with PKU |
| Protein in food | Tyrosine bound inside dietary protein | Protein foods supply both tyrosine and phenylalanine |
What is L-tyrosine, and what does it do?
L-tyrosine is an amino acid, one of the building blocks of protein. It has two main jobs. First, it is the starting material for a family of chemical messengers called catecholamines: dopamine, then norepinephrine, then epinephrine (adrenaline), which carry signals tied to focus, motivation, alertness and the body's response to stress. Second, tyrosine units inside a thyroid protein called thyroglobulin pick up iodine to become the thyroid hormones T4 and T3 (PMID 30886364). So the same amino acid sits behind both the stress-response messengers and the thyroid, which is one reason the cautions later in this article matter.
Tyrosine is not counted as an essential amino acid, because the body can make it from phenylalanine, which is essential and has to come from food. A varied diet with some protein usually covers both.
How does tyrosine become dopamine?
In two enzyme steps. The first, run by an enzyme called tyrosine hydroxylase, turns tyrosine into an intermediate; it's the slowest step, so it sets the pace for the whole line, and the messengers at the end of the line can slow it down when they build up (PMID 21176768). The second step finishes that intermediate into dopamine and needs vitamin B6 in its active form, pyridoxal-5-phosphate (P-5-P). Further enzymes then turn dopamine into norepinephrine and epinephrine. B6 is a helper in this line, not raw material. Our vitamin B6 page covers what the body needs and the safe ceiling.
Is tyrosine really a "dopamine supplement"?
Not in the way the phrase suggests. Tyrosine is a raw material for dopamine, not a dose of dopamine, and in most people the body already keeps enough on hand. The 2015 review put it plainly: tyrosine helps thinking "only when neurotransmitter function is intact and DA and/or NE is temporarily depleted" (PMID 26424423). In plain terms, topping up matters when demand is unusually high, not on an ordinary day. No amino acid raises dopamine to order.
What do studies show about tyrosine under stress?
Most of the human research tested tyrosine as a short-term buffer against a specific stressor, usually in military or lab settings and in small groups. The pattern is consistent: a modest help to thinking under pressure, little or nothing for mood, and nothing that looks like an everyday lift.
- In a crossover study, volunteers given 100 mg/kg of tyrosine before a 4.5-hour exposure to cold and low oxygen had fewer symptoms, better mood and fewer performance slips than on placebo, mostly among those who reacted worst to the conditions (PMID 2736402).
- Among 21 cadets on a demanding combat training course, the 10 who drank a protein drink with 2 g of tyrosine five times a day did better on a memory task and a tracking task than the 11 on a matched carbohydrate drink, and their systolic blood pressure dropped. Mood did not change (PMID 10230711).
- During cold-water immersion, 19 adults who ate a food bar with tyrosine (150 mg/kg before each of two immersions, 300 mg/kg total) answered more memory questions correctly than on placebo, which the researchers read as less of the usual drop in working memory (PMID 17585971).
- In a working-memory test, tyrosine improved performance on the harder version of the task but not the easy one, which fits the idea that it helps when the brain is working hardest (PMID 24379768).
A 2015 systematic review for the US military pulled the trials together: it found enough to make a weak case for tyrosine helping cognition under stress, but not enough to recommend it with confidence, and nothing for physical performance (PMID 26126245). Depletion studies point the same way from the other direction. When healthy women drank an amino-acid mix with phenylalanine and tyrosine removed, their mood dropped after a stressful public-speaking and arithmetic task about as much as it did when tryptophan was removed (PMID 10633491). In 16 adults, removing the two amino acids did not change mood or task behavior overall, but it blunted the brain's reward response on a scan (PMID 23995581).
How much tyrosine have studies used?
Trial doses were much larger than the amounts in most supplements, and they were usually set by body weight for a one-off challenge, not as a daily plan. This table shows what the studies actually gave.
| Study | Dose | Setting | What it found |
|---|---|---|---|
| Banderet & Lieberman 1989 (PMID 2736402) | 100 mg/kg, once | 4.5 hours of cold and low oxygen | Fewer symptoms and performance slips in the hardest-hit people |
| Deijen 1999 (PMID 10230711) | 2 g a day in a drink | Week-long combat course, 21 cadets | Better memory and tracking; lower systolic blood pressure; no mood change |
| Mahoney 2007 (PMID 17585971) | 150 mg/kg before each immersion, 300 mg/kg total | Cold-water immersion, 19 adults | Less of the cold-driven drop in working memory |
| Colzato 2013 (PMID 24379768) | Single dose before testing | Working-memory task | Helped the hard version, not the easy one |
At 100 to 150 mg/kg of body weight, those doses came to several grams at once, far above a typical capsule, and none were tested as a long-term daily habit (PMID 26126245).
Do you need to get tyrosine from food?
Usually the body handles this for you. Because the body makes tyrosine from phenylalanine, tyrosine isn't an essential amino acid, and protein foods supply both. A mixed diet with enough protein usually covers the body's needs. A supplement becomes a question mainly when protein intake is low or when someone is under heavy, sustained stress, and even then it is worth asking a clinician first.
L-tyrosine or N-acetyl L-tyrosine (NALT)?
N-acetyl L-tyrosine (NALT) is tyrosine with an acetyl group attached, which makes it dissolve far more easily, so it suits liquids and sprays. The open question is how much of it the body turns back into usable tyrosine. The clearest human data come from intravenous feeding in premature infants, not from an oral dose in healthy adults: in one study of 20 low-birth-weight newborns, 38% of the NALT given was excreted unchanged in the urine, and blood levels of NALT built up (331 micromol/L) while blood tyrosine stayed low (105 micromol/L) (PMID 7815670). We did not find a published study comparing oral NALT with plain tyrosine for raising blood tyrosine in healthy adults. So NALT is more soluble, but its advantage as a tyrosine source is not established. Our NALT page goes into more detail.
What are the side effects, and who should avoid it?
The trials above measured performance under stress over hours or days, so they say little about months of daily use, and no upper limit has been set for tyrosine. Taking it late in the day goes against the morning timing below. The real cautions are about who should avoid it and what it is taken with.
- MAO inhibitors. Do not combine tyrosine or phenylalanine products with this class of medicine. Together they can cause a dangerous rise in blood pressure. Dopa Tonic+ also contains PEA, another monoamine, which makes this caution more important.
- Stimulant medicines. Tyrosine feeds the same messenger system, so ask your prescriber before adding it to a stimulant.
- Thyroid medicine or an overactive thyroid. Because tyrosine is a thyroid-hormone building block, leave these products to your prescriber if you take thyroid medicine or have an overactive thyroid.
- PKU and limiting phenylalanine. Amino and Dopa Tonic+ contain L-phenylalanine, so they are not for anyone who has been told to limit phenylalanine, including people with PKU. Our phenylalanine page explains why.
- Pregnancy, nursing and children. Ask a clinician first. Most of these labels give no children's dose, and a child's amount always belongs with the child's doctor.
Take these products in the morning, on an empty stomach and away from protein meals, which compete with tyrosine for the same carrier into the brain. Keep them out of the evening. And use one tyrosine or phenylalanine product at a time rather than stacking several, the same one-at-a-time rule we follow across the catalog, explained in the safety rules behind our protocols.
Which ASDHelp products contain tyrosine?
Doses are copied from each label. These are structure-and-function supplements, not a plan for any condition. Count your B6 across everything you take: in every ASDHelp plan we keep total supplemental B6 at or under 25 mg a day for adults and 10 mg for children, unless a clinician sets a different amount, because high-dose B6 can damage sensory nerves (PMID 6308447).
- Neuro: 240 mg of free-form L-tyrosine per 2-tablet serving, in a broad brain formula that also carries acetyl-L-carnitine (500 mg), ashwagandha (100 mg), ginkgo (80 mg), DMAE (100 mg) and phosphatidylserine (50 mg). No added B6. Label directions: 2 tablets daily with food. Contains soy. No children's dose on the label, and the ashwagandha and ginkgo carry their own label cautions.
- Dopa Tonic+: an oral spray with 20 mg of N-acetyl L-tyrosine, 20 mg of L-phenylalanine and 8 mg of PEA per 2-spray serving, plus 2 mg of B6 as P-5-P. Label directions: 1 to 2 sprays three times a day, which at most adds up to 6 mg of B6 a day. Contains L-phenylalanine, and the label says to consult a professional before any use by minors.
- Spectrum Neurotransmitter Support: a powder whose typical amino acid profile lists 290 mg of tyrosine and 410 mg of phenylalanine per scoop (about 17.9 g), from 6 g of pea and rice protein, with NAC, DHA, CoQ10 and phosphatidylserine. No added B6. Label directions: one scoop for ages 4 and up; adults take it with a practitioner's guidance.
- Amino: nine free-form amino acids including 300 mg of L-phenylalanine per 4 capsules, the precursor the body turns into tyrosine, with 14 mg of B6 as P-5-P. It lists no tyrosine itself. Label directions: 4 capsules a day between meals. Not for anyone told to limit phenylalanine, including people with PKU. No children's dose on the label.
- Vitamin B6 P-5-P: 30 mg of active B6 per capsule, the cofactor for the last step to dopamine. One capsule is already above the 25 mg adult ceiling on its own, so it is for when B6 is the only gap, not an add-on to Amino or Dopa Tonic+. Adults, one capsule a day with food; under 18, practitioner-directed.
For a whole set built around attention and mental stamina, see our Focus and Clarity protocol, and for the bigger picture of how these amino acids turn into the brain's signals, see how amino acids become the brain's messengers. Tyrosine's sibling on the calming side is tryptophan; our tryptophan page covers that one.
Questions to take to your doctor
- Do I take an MAO inhibitor, a stimulant or thyroid medicine, or do I have an overactive thyroid, any of which would mean leaving tyrosine products to you?
- Have I been told to limit phenylalanine, which would rule out Amino and Dopa Tonic+?
- How much vitamin B6 do all of my supplements add up to, and are we under 25 mg a day?
- Given my diet and stress levels, is a tyrosine product likely to add anything, or is my protein intake already enough?
Sources
- Jongkees BJ et al. Effect of tyrosine supplementation on clinical and healthy populations under stress or cognitive demands: a review. J Psychiatr Res 2015. PMID 26424423
- Attipoe S et al. Tyrosine for mitigating stress and enhancing performance in healthy adult humans: a rapid evidence assessment. Mil Med 2015. PMID 26126245
- Banderet LE, Lieberman HR. Treatment with tyrosine, a neurotransmitter precursor, reduces environmental stress in humans. Brain Res Bull 1989. PMID 2736402
- Deijen JB et al. Tyrosine improves cognitive performance and reduces blood pressure in cadets after one week of a combat training course. Brain Res Bull 1999. PMID 10230711
- Mahoney CR et al. Tyrosine supplementation mitigates working memory decrements during cold exposure. Physiol Behav 2007. PMID 17585971
- Colzato LS et al. Working memory reloaded: tyrosine repletes updating in the N-back task. Front Behav Neurosci 2013. PMID 24379768
- Leyton M et al. Effects on mood of acute phenylalanine/tyrosine depletion in healthy women. Neuropsychopharmacology 2000. PMID 10633491
- Bjork JM et al. Dietary tyrosine/phenylalanine depletion effects on behavioral and brain signatures of human motivational processing. Neuropsychopharmacology 2014. PMID 23995581
- Van Goudoever JB et al. Amino acid solutions for premature neonates during the first week of life: the role of N-acetyl-L-cysteine and N-acetyl-L-tyrosine. JPEN J Parenter Enteral Nutr 1994. PMID 7815670
- Daubner SC, Le T, Wang S. Tyrosine hydroxylase and regulation of dopamine synthesis. Arch Biochem Biophys 2011. PMID 21176768
- Citterio CE, Targovnik HM, Arvan P. The role of thyroglobulin in thyroid hormonogenesis. Nat Rev Endocrinol 2019. PMID 30886364
- Schaumburg H et al. Sensory neuropathy from pyridoxine abuse. N Engl J Med 1983. PMID 6308447
These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure or prevent any disease. This article is educational and is not medical advice.