Phenylalanine

Related Terms

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

Background

Phenylalanine is available as a dietary supplement in the form of L-phenylalanine, D-phenylalanine, and DL-phenylalanine. L-phenylalanine is an essential amino acid in humans, and proteins contain only this form. The role of D-phenylalanine in humans is unclear. DL-phenylalanine is a manmade product made of 50 percent D-phenylalanine and 50 percent L-phenylalanine.
Depression is a common use for L-phenylalanine or DL-phenylalanine. Pain is a common use for D-phenylalanine. However, evidence is lacking to support this use.
Studies suggest that L-phenylalanine in combination with exposure to ultraviolet A (UVA) light or sunlight may help treat vitiligo, a condition in which there is a loss of skin pigment. This combination may also be used with a cream or gel of 10 percent phenylalanine, according to European studies.
Significant side effects include worsened Parkinson's disease with DL-phenylalanine and worsened movement disorders with L-phenylalanine.
People who have with phenylketonuria (PKU, a condition in which the body cannot break down phenylalanine) should follow a strict phenylalanine-restricted diet. Left untreated in mothers, PKU may lead to birth defects and health problems in babies. Higher phenylalanine levels in mothers have been found to increase the risk of birth defects.

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. GRADE *
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. GRADE *


DL-phenylalanine has been studied for potential benefits in adults with attention deficit hyperactivity disorder (ADHD). However, there are some conflicting results. Further research is needed in this area to support the use of phenylalanine for this condition.

 C


DL-phenylalanine has been studied for potential benefits in adults with attention deficit hyperactivity disorder (ADHD). However, there are some conflicting results. Further research is needed in this area to support the use of phenylalanine for this condition.

 C


D-phenylalanine in combination with other agents may help reduce symptoms of alcohol withdrawal. However, the effect of D-phenylalanine alone is unclear. Further study is needed before a firm conclusion can be made.

 C


D-phenylalanine in combination with other agents may help reduce symptoms of alcohol withdrawal. However, the effect of D-phenylalanine alone is unclear. Further study is needed before a firm conclusion can be made.

 C


D-phenylalanine has been found to increase the pain-relieving effects of acupuncture during tooth removal. More information is needed in this field before the use of phenylalanine as an additional therapy for dental pain can be supported.

 C


D-phenylalanine has been found to increase the pain-relieving effects of acupuncture during tooth removal. More information is needed in this field before the use of phenylalanine as an additional therapy for dental pain can be supported.

 C


L-phenylalanine has been found to improve mood in people who have major depression. A combination of L-phenylalanine and selegiline (L-deprenyl) has also been found to benefit those with this condition. DL-phenylalanine and D-phenylalanine have also been studied for depression, although the results are unclear. Further high-quality research is needed in this area.

 C


L-phenylalanine has been found to improve mood in people who have major depression. A combination of L-phenylalanine and selegiline (L-deprenyl) has also been found to benefit those with this condition. DL-phenylalanine and D-phenylalanine have also been studied for depression, although the results are unclear. Further high-quality research is needed in this area.

 C


L-phenylalanine has been studied in combination with ultraviolet A (UVA) light or exposure to sunlight for the treatment of vitiligo. European studies report that this combination may be used with a cream or gel of 10 percent phenylalanine. However, these preparations may not be available in the United States. Further study is needed in this area.

 C


L-phenylalanine has been studied in combination with ultraviolet A (UVA) light or exposure to sunlight for the treatment of vitiligo. European studies report that this combination may be used with a cream or gel of 10 percent phenylalanine. However, these preparations may not be available in the United States. Further study is needed in this area.

 C


Levels of phenylalanine have been found to be lower in people with attention deficit disorder (ADD) and attention deficit hyperactivity disorder (ADHD). D-phenylalanine has been studied for people with ADHD. However, it was found to lack benefit. Further high-quality research is needed in this area.

 D


Levels of phenylalanine have been found to be lower in people with attention deficit disorder (ADD) and attention deficit hyperactivity disorder (ADHD). D-phenylalanine has been studied for people with ADHD. However, it was found to lack benefit. Further high-quality research is needed in this area.

 D


D-phenylalanine has been found to lack effect on the enhancement of acupuncture for low back pain. Further high-quality studies are needed.

 D


D-phenylalanine has been found to lack effect on the enhancement of acupuncture for low back pain. Further high-quality studies are needed.

 D


D-phenylalanine has been found to lack benefit for people who have long-term pain. Research is limited in this area, and further study is needed.

 D


D-phenylalanine has been found to lack benefit for people who have long-term pain. Research is limited in this area, and further study is needed.

 D


The Cari Loder regime is a proposed method of treatment for multiple sclerosis (MS) that includes L-phenylalanine, lofepramine, and vitamin B12 injected into the vein. However, this combination has been found to lack effect on symptoms of MS.

 F


The Cari Loder regime is a proposed method of treatment for multiple sclerosis (MS) that includes L-phenylalanine, lofepramine, and vitamin B12 injected into the vein. However, this combination has been found to lack effect on symptoms of MS.

 F


Phenylalanine has been studied for phenylketonuria, with negative effects reported in terms of mood and brain function. A phenylalanine-restricted diet is advised in people with this disease.

 F


Phenylalanine has been studied for phenylketonuria, with negative effects reported in terms of mood and brain function. A phenylalanine-restricted diet is advised in people with this disease.

 F
* Key to grades

A: Strong scientific evidence for this use
B: Good scientific evidence for this use
C: Unclear scientific evidence for this use
D: Fair scientific evidence for this use (it may not work)
F: Strong scientific evidence against this use (it likley does not work)
* Key to grades

A: Strong scientific evidence for this use
B: Good scientific evidence for this use
C: Unclear scientific evidence for this use
D: Fair scientific evidence for this use (it may not work)
F: Strong scientific evidence against this use (it likley does not work)

Tradition / Theory

The below uses are based on tradition, scientific theories, or limited research. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. There may be other proposed uses that are not listed below.

Dosing

Adults (18 years and older)
For ADHD in adults, 50 milligrams of DL-phenylalanine has been taken by mouth three times daily, with a gradual increase to a maximum of 400 milligrams three times daily for 2-4 weeks.
For long-term pain, 250 milligrams of D-phenylalanine has been taken by mouth four times daily for four weeks.
For dental pain relief during tooth removal, 2-4 grams of D-phenylalanine has been taken by mouth 30 minutes before acupuncture.
For depression, 500 milligrams of L-phenylalanine has been taken by mouth twice daily (morning and noon), then increasing up to 14 grams daily. A dose of 250 milligrams of L-phenylalanine has been taken by mouth once daily for 28-96 days. D-phenylalanine has been taken by mouth at doses of 100-600 milligrams daily for 15 days to four weeks. DL-phenylalanine has been taken by mouth at doses of 50-200 milligrams daily for 15-30 days.
For low back pain, 1.5 grams of D-phenylalanine has been taken by mouth daily in three divided doses (0.5 grams after the evening meal and at bedtime on the day before acupuncture, and 0.5 grams after breakfast on the day of acupuncture), or four grams has been taken by mouth in a single dose 30 minutes before acupuncture.
For phenylketonuria (PKU), phenylalanine has been taken by mouth daily for four weeks at a dose based on sex and weight (4,000 milligrams for males under 60 kilograms; 4,500 milligrams for males 60-94 kilograms; 5,000 milligrams for males over 95 kilograms; 2,500 milligrams for females under 50 kilograms; 3,000 milligrams for females 50-84 kilograms; and 3,500 milligrams for females over 85 kilograms).
For vitiligo, 50-100 milligrams of L-phenylalanine per kilogram of body weight has been taken by mouth once daily (with water after or during breakfast with a low amount of protein, such as two slices of brown bread with jam and a cup of tea). L-phenylalanine has been taken by mouth at a dose of 50 milligrams per kilogram three times weekly for up to three months. A gel containing 10 percent phenylalanine has been applied to the skin from April through October. A cream containing 10 percent phenylalanine has been applied to the skin.

Safety

The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.

Interactions

Interactions with Drugs
Phenylalanine may interfere with the way the body processes certain drugs using the liver's "cytochrome P450" enzyme system. As a result, the levels of these drugs may be altered in the blood, and may cause altered effects or potentially serious adverse reactions. People using any medications should check the package insert, and speak with a qualified healthcare professional, including a pharmacist, about possible interactions.
Phenylalanine may also interact with agents for the heart, agents for mental disorders, agents that affect the immune system, antidepressants (monoamine oxidase inhibitors [MAOIs]), baclofen, carbidopa/levodopa (Sinemet?), cefdinir, central nervous system (CNS) stimulants, clobetasol, levodopa, lofepramine, pain relievers, sapropterin dihydrochloride (Medi-Span?), and sedatives.

Attribution

This information is based on a systematic review of scientific literature edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).

Bibliography

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