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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.
Last reviewedAugust 2013by EBSCO CAM Review Board
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