High Purity L-Tyrosine & L-Phenylalanine
Pure, lab-tested L-Tyrosine & L-Phenylalanine (99+% purity) in a bovine gelatin capsule. Nothing else.
Servings per container: 90
Serving size: 1 capsule
Each capsule contains:
Other ingredients: gelatin (bovine)
L-Tyrosine & L-Phenylalanine - Dopamine & Thyroid Precursors
The most significant and studied aspects of L-Tyrosine and L-Phenylalanine are that they are both amino acids that are precursors to Dopamine, and Thyroid hormone.
The building blocks of thyroid hormone production:
Iodine + Tyrosine --> monoiodotyrosine (T1) and diiodotyrosine (T2)
T1 + T2 --> T4 (thyroxine) & T3 (triiodothyronine, needs selenium too)
The biological pathway to dopamine (mediated by enzymes):
L-Phenylalanine --> L-Tyrosine --> L-Dopa --> Dopamine.
Dopamine is one of those buzzwords that gets thrown around very often in day-to-day scenarios. Not always completely out of context, but many times missing the larger picture.
While dopamine is involved in us getting rewarded and excited by things, it also plays an important role in us not getting over-rewarded, or feeling rewarded or stimulated by things that are not necessarily serving us for the better.
The ways that this is studied in clinical trials, interestingly, is by creating a Tyrosine and Phenylalanine deficiency in patients or animal models and then applying the stimulus or variable that they are wishing to test. Some fascinating results of studies like this have been quicker reaction time and less inclination towards smoking.
Another fascinating aspect of L-Tyrosine is that it is a crucial component in the production of melanin. "The critical step in melanin biogenesis is the oxidation of tyrosine by the enzyme tyrosinase." Riley, P. (1997).
This means that Tyrosine in a sense is a light-absorbing amino acid, and helps us produce pigment for our hair and skin. It's important to note as well, that our exposure to natural light also helps promote the conversion of tyrosine into dopamine.
It may seem that Tyrosine is the main goal - but here's why consuming Phenylalanine is still beneficial and important:
While Tyrosine can be synthesized in the human body, it is created by converting Phenylalanine, which cannot be synthesized and must come from the diet.
Therefore, we can deduce the importance of consuming Phenylalanine but also understand the importance of Tyrosine itself. Consuming both amino acids allows the body to have some supply of Tyrosine, but also to have a reserve of its building block in the case it should need to convert more.
Moreover, a study by Wang, H. L. (1962) called "Effect of dietary phenylalanine and tryptophan on brain serotonin" showed that not dietary Tyrosine, but Phenylalanine consumption was able to lower body and brain serotonin. If you have studied or are a fan of the work of Dr. Ray Peat, and his extensive explanations on serotonin and its harmful effects in excess, then you will appreciate the value in that.
As Fernstrom, J. (2007) says "physiologic factors that influence brain pools of these amino acids, notably diet, influence their rates of conversion to neurotransmitter products, with functional consequences."
L-Phenylalanine & L-Tyrosine Benefits:
- Dopamine synthesis
- Thyroid hormone production support
- Improved motivation
- Improved focus
- Attention deficit assistance
- Regulation of reward-seeking behavior
- May assist with addiction-alleviation
- Aids melanin production
- Adrenal support
- Prolactin lowering
- Serotonin lowering
1. Coull JT, Hwang HJ, Leyton M, Dagher A. Dopamine precursor depletion impairs timing in healthy volunteers by attenuating activity in putamen and supplementary motor area. J Neurosci. 2012 Nov 21;32(47):16704-15. doi: 10.1523/JNEUROSCI.1258-12.2012. PMID: 23175824; PMCID: PMC6621775.
2. During MJ, Acworth IN, Wurtman RJ. Phenylalanine administration influences dopamine release in the rat's corpus striatum. Neurosci Lett. 1988 Oct 31;93(1):91-5. doi: 10.1016/0304-3940(88)90018-3. PMID: 3211373.
3. Roiser JP, McLean A, Ogilvie AD, Blackwell AD, Bamber DJ, Goodyer I, Jones PB, Sahakian BJ. The subjective and cognitive effects of acute phenylalanine and tyrosine depletion in patients recovered from depression. Neuropsychopharmacology. 2005 Apr;30(4):775-85. doi: 10.1038/sj.npp.1300659. PMID: 15688090; PMCID: PMC2631648.
4. Hardman CA, Herbert VM, Brunstrom JM, Munafò MR, Rogers PJ. Dopamine and food reward: effects of acute tyrosine/phenylalanine depletion on appetite. Physiol Behav. 2012 Mar 20;105(5):1202-7. doi: 10.1016/j.physbeh.2011.12.022. Epub 2011 Dec 30. PMID: 22230253.
5. Hitsman B, MacKillop J, Lingford-Hughes A, Williams TM, Ahmad F, Adams S, Nutt DJ, Munafò MR. Effects of acute tyrosine/phenylalanine depletion on the selective processing of smoking-related cues and the relative value of cigarettes in smokers. Psychopharmacology (Berl). 2008 Mar;196(4):611-21. doi: 10.1007/s00213-007-0995-5. Epub 2007 Nov 25. PMID: 18038222.
6. Lou HC. Dopamine precursors and brain function in phenylalanine hydroxylase deficiency. Acta Paediatr Suppl. 1994 Dec;407:86-8. doi: 10.1111/j.1651-2227.1994.tb13461.x. PMID: 7766968.
7. Fernstrom JD, Fernstrom MH. Tyrosine, phenylalanine, and catecholamine synthesis and function in the brain. J Nutr. 2007 Jun;137(6 Suppl 1):1539S-1547S; discussion 1548S. doi: 10.1093/jn/137.6.1539S. PMID: 17513421.
8. Riley PA. Melanin. Int J Biochem Cell Biol. 1997 Nov;29(11):1235-9. doi: 10.1016/s1357-2725(97)00013-7. PMID: 9451820.
9. Iuvone PM. Regulation of retinal dopamine biosynthesis and tyrosine hydroxylase activity by light. Fed Proc. 1984 Sep;43(12):2709-13. PMID: 6147273.
10. Elkin RG, Featherston WR, Rogler JC. Effects of dietary phenylalanine and tyrosine on circulating thyroid hormone levels and growth in the chick. J Nutr. 1980 Jan;110(1):130-8. doi: 10.1093/jn/110.1.130. PMID: 7354377.
11. H.L. Wang, V.H. Harwalkar, H.A. Waisman, Effect of dietary phenylalanine and tryptophan on brain serotonin, Archives of Biochemistry and Biophysics, Volume 97, Issue 1, 1962, Pages 181-184, ISSN 0003-9861, https://doi.org/10.1016/0003 9861(62)90062-0.