Phenylalanine is an amino acid. It is not made naturally in the body. Protein is a natural source of phenylalanine and other amino acids. Foods such as meat, fish, eggs, cheese and milk are all a source of L-phenylalanine. D-phenylalanine is man-made. DL-phenylalanine is a combination of the D and L forms.
Phenylalanine converts to an amino acid which produces chemical messengers in the brain (e.g. norepinephrine). It is thought that norepinephrine helps regulate how we cope with stress.
There is very little scientific evidence on phenylalanine for the treatment of depression. More studies of better quality are needed.
A 1979 study tested the effectiveness of DL-phenylalanine compared to an anti-depressant drug. Phenylalanine was as effective as the anti-depressant. The study had no control group. It had a very small number of participants.
People should not take phenylalanine if they have the genetic disorder phenylketonuria or if they are pregnant.
Dietary supplements may have negative interactions with prescribed medications or other supplements. They should always be taken under the supervision of a health care professional.
Phenylalanine is available at some pharmacies, supplement and body building stores.
There is not enough evidence at this stage to recommend phenylalanine as a treatment for depression.
Last updated and reviewed: 17 February 2015