In this blog post, I will walk you through the potential health benefits of N-acetyl L-tyrosine, an amino acid precursor to neurotransmitters that help with cognitive function. Find out why it’s one of the ingredients in our Seneca Nootropic Complex.
What is N-Acetyl L-Tyrosine?
N-Acetyl L-Tyrosine (NALT) is a form of L-Tyrosine with an added acetyl group. The added acetyl group makes NALT more bioavailable (so more can be absorbed in the gut). This helps NALT more easily cross the blood-brain barrier, so it can move into the brain.
Tyrosine is a precursor to the Catecholamines, which are dopamine, norepinephrine, and epinephrine. All 3 act as neurotransmitters, with norepinephrine and epinephrine also being hormones.
All 3 of these neurotransmitters are vital for cognitive processing, focus, motivation, and memory. Both stress and not getting enough tyrosine through the diet can affect our ability to produce these neurotransmitters. Fortunately, supplementing with tyrosine can correct any reduction in cognitive function and deficiency in catecholamine levels caused by stress (1).
Tyrosine is also used as the base from which we make all the thyroid hormones T4, T3, and reverse T3. Thyroid hormones are used by every cell in the body and set our metabolic rate. They can be thought of a bit like an accelerator on a car. The higher our thyroid hormones (at least levels of T3 and T4, as reverse T3 acts a little like a break), the more energy we have.
To make the thyroid hormones, 4 molecules of iodine are added to Tyrosine to make T4, and 3 molecules of iodine are added to Tyrosine to make T3 and reverse T3 (2).
Ensuring Adequate Tetrahydrobiopterin Levels
Tyrosine is considered a conditionally essential amino acid. This means that we can make it from the amino acid phenylalanine, but it requires essential resources to make the conversion. The essential resource is Tetrahydrobiopterin (BH4, or Biopterin for short), which is also vital for the production of serotonin and melatonin. Biopterin is also important for Nitric Oxide which is needed in the blood vessels and neurons to relax and increase blood flow and oxygen delivery (3).
Biopterin also stops Nitric Oxide from turning into peroxynitrite, which is formed from the free radical superoxide and is a powerful oxidant that can cause a lot of damage to the body. So ensuring we have adequate levels of Tyrosine to make both the Catecholamines and Thyroid Hormones that we need means we can avoid having to use up body stores of biopterin.
N-Acetyl L-Tyrosine (NALT) vs L-Tyrosine
Comparing NALT to L-Tyrosine is an active discussion in supplementation circles, especially in the nootropics niche. NALT is more soluble and more stable at blood PH, so it should be more bioavailable than L-Tyrosine. However, a ‘should’ doesn’t mean that it actually is.
For example, there have been several studies showing high increases in plasma tyrosine levels following oral supplementation with L-Tyrosine. They have shown increases ranging from 130% – 276% percent in blood tyrosine levels. The studies used 100mg/kg to 200mg/kg of L-Tyrosine per day, so for a 70kg adult that would equal 7,000mg of L-Tyrosine per day (4-7).
So when you compare that to a further study that supplemented with 5000mg of NALT per day but only found that it increased blood tyrosine levels by 25% (8), with most of the NALT being excreted in the urine, it would seem that obviously, L-Tyrosine is the better option. However, I actually think differently, and the reason for that is that in this experiment the NALT was actually infused through an IV.
The study makes it clear that if you want to use an IV to increase Tyrosine levels, such as for patients who for a medical reason can’t eat, then it should only be done using much lower levels of Tyrosine along with ‘other amino acids, fat, and carbohydrates’, not just NALT on its own.
As a further study showed, the reason for this is that the enzymes necessary for removing the acetyl group from NALT are found in the largest concentration in the gut. And this is completely bypassed by IV and that the remainder of the enzymes in the body (mostly in the kidney) become saturated when high doses of NALT are infused, so they can’t deacetylate all of the NALT. So instead of the NALT being converted to L-Tyrosine in the kidneys, it instead gets excreted by them (9). So using smaller concentrations of NALT mixed in with fats, carbs, and other Amino Acids likely works much better.
Also, there’s a further reason I prefer NALT over L-Tyrosine, and that is that people seem to notice a bigger difference with NALT over just L-Tyrosine. Whilst this is anecdotal over ‘real science’, real science as we’ve seen can sometimes have problems, just as sometimes anecdotal data can give a really good picture. So whilst I think it’s important to look at all the experimental data we have available, it’s also important to look at the overall picture and on that basis, I prefer to recommend NALT.
Show Me The Science!
Tyrosine as a Nootropic
The first thing that the science behind tyrosine shows is that Dopamine, Norepinephrine and Epinephrine deficiencies can occur due to tyrosine deficiencies, and tyrosine supplementation can correct that.
Tyrosine supplementation (such as with our Seneca Nootropic Complex) can also help the body maintain adequate levels when the catecholamine neurotransmitters are used up at faster rates than normal during stress, be that chronic or acute stress (10).
However, whilst it can correct deficiencies, Tyrosine supplementation on its own is unlikely to be able to increase neurotransmitter levels over what is ‘normal’ for your brain. This explains why sometimes people can take tyrosine and experience a plateau effect after a week or so. This is where they stop feeling an improvement and often people think they’ve released a tolerance. However, it seems more likely that they have probably corrected any preexisting deficiency, and have reached the peak benefit for them from just tyrosine. Having said that, tyrosine is still an important part of the overall Nootropic picture, and even when any deficiency is corrected.
Tyrosine will also offer help during periods of stress when neurotransmitters are used up more quickly than normal. This is highlighted in the following studies which are all conducted under situations designed to put the subjects under stress.
Related article: What are nootropics?
Tyrosine and Cognitive Flexibility
Cognitive flexibility can be thought of a little bit like brain fitness. It measures how well someone can adapt to new situations and stimuli. This double-blind placebo-controlled study tested 22 healthy adults in a task-switching paradigm. This means that the subjects were tested on one type of cognitive test, such as visual recall, and then they swapped to another different type of test, such as mental arithmetic and then back again and so on.
At the end of the study, the researchers found that the group that had supplemented with tyrosine performed significantly better on the tests than those given a placebo (11).
In a further study, tyrosine supplementation was able to improve the performance of adults who had been sleep-deprived, although to a lesser extent than amphetamines which were also tested during the experiment (12). Tyrosine also helped increase ‘deep thinking’, great for musing on the meaning of life! (13).
Improved cognitive performance following exercise and heat stress
This study tested football players (as in soccer) on a 90-minute football simulated test in a warm environment of 77°F (25°C). They gave half of the subjects tyrosine before the task and then tested them halfway through, and again at the end of the 90-minute test.
The researchers found that both cognitive performance and mental effort were increased in the subjects that had been given the tyrosine at both the halfway and full-time tests (14).
Cognitive function, blood pressure and heart rate during stress
A Dutch study looked at the ability of tyrosine supplementation to improve cognitive function, heart rate, and blood pressure. The researchers put 16 healthy young subjects through a number of cognitive tests after the subjects had been exposed to an acute stressor. In this case, the stressor was exposure to a loud noise of 90dB.
The subjects went through 2 tests, the second one day after the first, one test being with tyrosine supplementation and the other without as a control. The researchers found that the subjects scored better on cognitive tests after they had supplemented with tyrosine, and they also had lower diastolic blood pressure. However, there was no difference in systolic blood pressure or heart rate, between the two tests (15).
As you’ve learned in this article, choosing N-acetyl L-tyrosine over l-tyrosine has a lot of upsides. You get to enjoy a cognitive boost even during stressful times, such as sustained work periods and sleep loss. If this is something you need help with right now, consider supplementing with NALT.
(1) Adrian Hase, Sophie E Jung, Marije aan het Rot, Behavioral and cognitive effects of tyrosine intake in healthy human adults Pharmacol Biochem Behav. 2015 Jun;133:1-6.
(2) Nermin Kuzkaya, Norbert Weissmann, David G Harrison, Sergey Dikalov, Interactions of peroxynitrite, tetrahydrobiopterin, ascorbic acid, and thiols: implications for uncoupling endothelial nitric-oxide synthase, Comparative Study J Biol Chem. 2003 Jun 20;278(25):22546-54
(3) Chemistry of Thyroid Hormones, Colorado State University, http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/thyroid/chem.html
(4) Glaeser, B.S., et al., Elevation of plasma tyrosine after a single oral dose of L-tyrosine. Life Sci, 1979. 25 (3): p. 265-71.
(5) Smith, M.L., et al., Randomised controlled trial of tyrosine supplementation on neuropsychological performance in phenylketonuria. Arch Dis Child, 1998. 78 (2): p. 116-21.
(6) Pietz, J., et al., Effect of high-dose tyrosine supplementation on brain function in adults with phenylketonuria. J Pediatr, 1995. 127 (6): p. 936-43.
(7) Lykkelund, C., et al., Increased neurotransmitter biosynthesis in phenylketonuria induced by phenylalanine restriction or by supplementation of unrestricted diet with large amounts of tyrosine. Eur J Pediatr, 1988. 148 (3): p. 238-45.
(8) Magnusson, I., et al., N-acetyl-L-tyrosine and N-acetyl-L-cysteine as tyrosine and cysteine precursors during intravenous infusion in humans. Metabolism, 1989. 38 (10): p. 957-61.
(9) J.B. Van Goudoever, E.J. Sulkers, M. Timmerman, J.G.M. Huijmans, K. Langer, V.P. Carnielli and P.J.J. Sauer, Amino Acid Solutions for Premature Neonates During the First Week of Life: The Role of N-Acetyl-L-Cysteine and N-Acetyl-L-Tyrosine, Journal of Parenteral and Enteral Nutrition.
(10) Bryant J. Jongkees a, Bernhard Hommel a, Simone Kühn b, Lorenza S. Colzato a, Effect of tyrosine supplementation on clinical and healthy populations under stress or cognitive demandsdA review, Journal of Psychiatric Research 70 (2015) 50-57
(11) L. Steenbergen, R. Sellaro, L. Colzato, Tyrosine promotes cognitive flexibility: Evidence from proactive vs. reactive control during task switching performance, j.neuropsychologia, 2015.01.022
(12) Richard A Magill, William F Waters, George A Bray, Julia Volaufova, Steven R Smith, Harris R Lieberman, Nancy McNevin, Donna H Ryan, Effects of tyrosine, phentermine, caffeine D-amphetamine, and placebo on cognitive and motor performance deficits during sleep deprivation, Nutr Neurosci. 2003 Aug;6(4):237-46.
(13) Food for creativity: tyrosine promotes deep thinking, Lorenza S Colzato, Annelies M de Haan, Bernhard Hommel, Psychol Res. 2015 Sep;79(5):709-14.
(14) Coull N.A, Watkins S.L, Aldous J.W, Warren L.K, Chrismas B.C, Dascombe B, Mauger A.R, Abt G, Taylor L, Effect of tyrosine ingestion on cognitive and physical performance utilising an intermittent soccer performance test (iSPT) in a warm environment, European Journal of Applied Physiology, 2015 Feb;115(2):373-86.
(15) J B Deijen 1, J F Orlebeke, Effect of tyrosine on cognitive function and blood pressure under stress, Brain Res Bull. 1994;33(3):319-23.