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Phenylalanine is an essential amino acid found in meat, dairy, and beans. It has been used to treat chronic pain and ease symptoms of depression. Phenylalanine can be taken as a pill or powder. It can also be applied to the skin as a cream.


100 to 200 milligrams once daily

What Research Shows

Not Enough Data to Assess

  • Multiple sclerosis A1
  • Vitiligo B1

Editorial process and description of evidence categories can be found at EBSCO NAT Editorial Process.

Safety Notes

It is likely safe for most adults to take L-phenylalanine in small doses for a short time. Not enough studies have been done to say whether it is safe to use D-phenylalanine. Women who are pregnant or trying to become pregnant or who are breastfeeding should not take high amounts of phenylalanine.


Talk to your doctor about any supplements or therapy you would like to use. Some can interfere with treatment or make conditions worse, such as:



A. Multiple Sclerosis

A1. Wade DT, Young CA, et al. A randomised placebo controlled exploratory study of vitamin B-12, lofepramine, and L-phenylalanine (the “Cari Loder regime”) in the treatment of multiple sclerosis. J Neurol Neurosurg Psychiatry. 2002;73(3):246-249.

B. Vitiligo

B1. Szczurko O, Boon HS. A systematic review of natural health product treatment for vitiligo. BMC Dermatol. 2008 May 22;8:2.

Last reviewed July 2019 by EBSCO NAT Review Board Eric Hurwitz, DC  Last Updated: 5/1/2020