Phenylalanine is one of the amino
acids which the body cannot manufacture itself, but must acquire from food. It is abundant
in meats and cheese. Phenylalanine is a precursor of tyrosine, and together they lead to
the formation of thyroxine or thyroid hormone, and of epinephrine and norepinephrine which
is converted into a neurotransmitter, a brain chemical which transmits nerve impulses.
This neurotransmitter is used by the brain to manufacture norepinephrine which promotes
mental alertness, memory, elevates mood, and suppresses the appetite very effectively.
In one study, 100-500 milligrams of phenylalanine taken every day for two weeks
completely eliminated patients depression. These people where depressed from a variety of
causes, including drug abuse and schizophrenia and some from no apparent cause, and the
amino acid seemed to work especially well for them all.
Along with another amino acid, tryptophan, phenylalanine governs the release of an
intestinal hormone called cholecystokinin, known as CCK. This hormone signals the brain to
feel satisfied after eating. People given CCK stop eating and feel full sooner. Various
studies have shown Phenylalanine's ability to decrease chronic back and dental pain and
the pain associated with migraines and menstruation in a non-toxic and non-addictive
manner.
Phenylalanine comes in two forms which are mirror images of each other: L-phenylalanine
which has a nutritional value, and D-phenylalanine which has painkilling and depression
alleviating properties which are attributed to its ability to block the breakdown of
enkephalins, the brains natural pain killers. A third form, DL-phenylalanine, is a 50/50
mixture of these two forms. Phenylalanine activity is enhanced by additional Vitamin B 6,
especially in studies on depression.
Phenylalanine deficiency can cause bloodshot eyes, cataracts and behavioral changes.
Nutritional researchers recommend keeping intake of supplemental forms of phenylalanine to
no more than 2.4 grams per day. Overuse of phenylalanine supplements can cause anxiety,
headaches and hypertension, and are contraindicated for pregnant woman, those who suffer
from anxiety attacks, high blood pressure, PKU, pigmented melanoma, or anyone taking an
anti-depressant containing MAO inhibitors.