Principal Proposed Uses
Phenylalanine occurs in two chemical forms: L-phenylalanine , a natural amino acid found in proteins; and its mirror image, D-phenylalanine , a form synthesized in a laboratory. Some research has involved the L-form, others the D-form, and still others a combination of the two known as DL-phenylalanine.
In the body, phenylalanine is converted into another amino acid called tyrosine . Tyrosine in turn is converted into L-dopa, norepinephrine, and epinephrine, three key neurotransmitters (chemicals that transmit signals between nerve cells). Because some antidepressants work by raising levels of norepinephrine, various forms of phenylalanine have been tried as a possible treatment for depression.
D-phenylalanine (but not L-phenylalanine) has been proposed to treat chronic pain. It blocks enkephalinase , an enzyme that may act to increase pain levels in the body.
L-phenylalanine is an essential amino acid, meaning that we need it for life and our bodies can't manufacture it from other chemicals. It is found in protein-rich foods such as meat, fish, poultry, eggs, dairy products, and beans. Provided you eat enough protein, you are likely to get enough L-phenylalanine for your nutritional needs. There is no nutritional need for D-phenylalanine.
It is best not to take your phenylalanine supplement at the same time as a high-protein meal, as it may not be absorbed well.
What Is the Scientific Evidence for Phenylalanine?
Unfortunately, there have not been any double-blind, placebo -controlled studies of phenylalanine for depression. This is too bad, since without such evidence we can't be sure that the supplement is actually effective. (For information on why such studies are so important, see Why Does This Database Rely on Double-blind Studies? )
The long-term safety of phenylalanine in any of its forms is not known. Both L- and D-phenylalanine must be avoided by those with the rare metabolic disease phenylketonuria (PKU).
The maximum safe dosages of phenylalanine have not been established for young children, pregnant or nursing women, or those with severe liver or kidney disease.
Interactions You Should Know About
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- Reviewer: EBSCO CAM Review Board
- Review Date: 07/2012 -
- Update Date: 07/25/2012 -