Other name(s):

a-amino-b-phenyl-propionic acid

Unproven claims

There may be benefits that have not yet been proven through research.

Phenylalanine is an essential amino acid. It is found in high-protein foods. It may improve memory and learning ability. It may enhance mood and alertness. It may help treat some types of depression. It’s been used to help treat schizophrenia and Parkinson disease.

Phenylalanine is used in some artificial sweeteners. It tends to decrease appetite. It’s been used to treat obesity.

It’s also claimed to boost pain tolerance in premenstrual syndrome (PMS) and migraine headaches.

Recommended intake

The FDA says that the supplement may be harmful.

Side effects, toxicity, and interactions

High levels of phenylalanine are linked with the genetic issue phenylketonuria. In infants with this issue, high levels of phenylalanine cause intellectual problems. It can also lead to seizures and delays in development.

Pregnant people with the condition who don’t avoid phenylalanine during pregnancy may give birth to a baby with signs of phenylketonuria.

Don't take this supplement if any of these are true:

  • You have phenylketonuria.

  • You have melanoma (pigmented type).

  • You have tyrosinemia (type I or II).

  • You take monoamine oxidase inhibitors (MAOIs).

  • You are pregnant or breastfeeding.

Online Medical Reviewer: Brittany Poulson MDA RDN CD CDE
Online Medical Reviewer: Diane Horowitz MD
Online Medical Reviewer: Heather M Trevino BSN RNC
Date Last Reviewed: 6/1/2021