Phenylalanine is an essential amino acid that is metabolized into a brain neurotransmitter, norepinephrine, with the help of Vitamins C and B-6. Norepinephrine helps stimulate the release of growth hormone from the pituitary gland and is involved in mood, clarity of thought, and alertness. Phenylalanine is a precursor to adrenaline (epinephrine), the adrenal hormone which, along with norepinephrine, regulates the fight or flight response.
Many of the observed effects of phenylalanine relate to mental functioning. This amino acid is experimentally used to improve learning and memory, and as an antidepressant. It promotes feelings of alertness and aids in obesity by suppressing appetite. It forms the artificial sweetener aspartame (Nutrasweet) when chemically combined with aspartic acid.
Phenylalanine is commercially available in two forms, L and DL. The two differ in purpose only in that the DL form lessens pain associated with migraines, premenstrual syndrome (PMS) and arthritis. The D-isomer is incorporated into receptors, thus blocking pain. In his book, Natural Prescriptions, Dr. Robert Giller says that many of his patients have found phenylalanine to be the most exciting PMS treatment he has found for the moodiness and depression that precede a womanís period.
The inability to metabolize phenylalanine results in the metabolic disorder, PKU. Those suffering from this disorder must halt or at least cut back on phenylalanine consumption to prevent serious mental retardation. Phenylalanine should not be used by pregnant women, persons with panic disorders, high blood pressure, or pre-existing pigmented melanoma.