Phenylalanine is an essential amino acid that must be obtained from the diet. In the body it is transformed into tyrosine, which is in turn transformed into a variety of hormonal neurotransmitters, such as epinephrine (or adrenaline), norepinephrine, dopamine, dopa, etc. Phenylalanine is marketed in the L, D and the combined LD form.


  • Controls the appetite and body weight
  • Possesses antidepressant properties
  • In the D but not the L form, it may help back and other pains

It should not be taken by persons with high blood pressure, the rare metabolic disorder known as phenylketonuria, or patients under treatment with monoamine oxidase inhibitors.

High doses may cause anxiety, headache, and even mildly elevated high blood pressure. There are indications that the use of phenylalanine with antipsychotic drugs may increase the risk of developing tardive dyskinesia.