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Question mark: This treatment has not been properly researched. It is not possible to say whether they are useful or not.

What is it?

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.

How does it work?

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.

Is it effective?

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.

Are there any disadvantages?

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.

Where do you get it?

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.

Key references

  • Beckmann H, Athen D, Olteanu M, Zimmer R. DL-phenylalanine versus imipramine: a double-blind study. Archiv fur Psychiatrie und Nervenkrankheiten 1979; 227: 49-58.

Last updated and reviewed: 17 February 2015