Phenylalanine

background

Phenylalanine is commercially available as a dietary supplement in the forms of L-phenylalanine, D-phenylalanine, and DL-phenylalanine. L-phenylalanine is an essential amino acid in humans, and proteins contain only this form. According to experts, L-phenylalanine likely is likely safe when consumed in amounts that typically occur in food. The role of D-phenylalanine in humans is unclear. DL-phenylalanine is a synthetic product made of 50% D-phenylalanine and 50% L-phenylalanine.
Good scientific evidence (reported primarily in the 1970s and 1980s) supports the use of L-phenylalanine or DL-phenylalanine to treat depression. Good scientific evidence also supports the use of L-phenylalanine, in combination with exposure to ultraviolet A light or sunlight, to treat vitiligo, a skin condition characterized by patchy loss of skin pigments.
The Cari Loder regime is a treatment for multiple sclerosis (MS) that includes phenylalanine, as well as lofepramine (an antidepressant not available in the United States), and intramuscular injections of vitamin B12. The treatment was developed by Cari Loder, a research scientist and MS patient, and it was described in the popular literature. Subsequent clinical research failed to produce data supporting the use of the regime to treat MS.
Areas of current research interest regarding phenylalanine include diagnosis, dietetics, nutrition, and physiology.

Related Terms

Alpha-aminohydrocinnamic acid, beta-phenylalanine, Cari Loder regime, DLPA, DL-phenylalanine, D-phenylalanine, L-phenylalanine.

evidence table

These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.
 
Depression (Grade: B)
A number of reports, published primarily in the 1970s and 1980s, provide good evidence for the use of L-phenylalanine or DL-phenylalanine in treating depression. Additional research is needed before a conclusion can be made.
Vitiligo (Grade: B)
Several studies suggests that L-phenylalanine, in combination with exposure to ultraviolet A light or sunlight, may help treat vitiligo (patches of unpigmented skin). Additional studies are needed in this area.
Attention deficit hyperactivity disorder (adults) (Grade: C)
Limited research suggests that DL-phenylalanine may have positive effects on mood in adults with attention-deficit hyperactivity disorder (ADHD). Additional research is needed before a conclusion can be made
Dental anesthesia (Grade: C)
Preliminary research suggests that D-phenylalanine may enhance the effect of acupuncture as anesthesia during tooth extraction. Additional research is necessary before a conclusion can be made.
Attention deficit hyperactivity disorder (children) (Grade: D)
Limited research suggests that D-phenylalanine may be ineffective for treating attention-deficit hyperactivity disorder (ADHD) in children. Additional research is needed in this area.
Chronic pain (Grade: D)
Limited research suggests that D-phenylalanine may be ineffective for treating various form of chronic pain. Additional research is needed before a conclusion can be made.
Low back pain (Grade: D)
Preliminary research suggests that D-phenylalanine may not enhance acupuncture's effect on low back pain. Additional research is necessary before a conclusion can be made.
Multiple sclerosis (Grade: F)
Limited research suggests that Cari Loder's regime (L-phenylalanine, lofepramine (an antidepressant not available in the United States), and intramuscular vitamin B12) likely lacks an effect on disabilities associated with multiple sclerosis. Additional research is needed before a conclusion can be made.