Uses

L-phenylalanine (LPA) serves as a building block for the various proteins that are produced in the body. LPA can be converted to L-tyrosine (another amino acid) and subsequently to L-dopa, norepinephrine, and epinephrine. LPA can also be converted (through a separate pathway) to phenylethylamine, a substance that occurs naturally in the brain and appears to elevate mood.

What Are Star Ratings?

This supplement has been used in connection with the following health conditions:

Used for Why
2 Stars
Depression
3 to 4 grams L-phenylalanine or 150 to 200 mg of DL-phenylalanine daily
In one study, depressed people given L-phenylalanine experienced results comparable to those produced by an antidepressant.

L-phenylalanine is another amino acid that converts to mood-affecting substances (including phenylethylamine and norepinephrine). Preliminary research reported that L-phenylalanine improved mood in most of the depressed people studied.DLPA is a mixture of the essential amino acid L-phenylalanine and its synthetic mirror image, D-phenylalanine. DLPA (or the D- or L- form alone) reduced depression in 31 of 40 people in a preliminary trial. Some doctors suggest a one-month trial with 3-4 grams per day of phenylalanine for people with depression, although some researchers have found that even very low amounts-75-200 mg per day-were helpful in preliminary trials. In one double-blind trial, depressed people given 150-200 mg of DLPA per day experienced results comparable to that produced by an antidepressant drug.

2 Stars
Low Back Pain
1,500 to 2,500 mg per day of DL-Phenylalanine
Several studies suggest that a synthetic version of phenylalanine called D-phenylalaline, may reduce pain by decreasing the enzyme that breaks down endorphins.

Several animal studies and some research involving humans suggest that a synthetic version of the natural amino acid phenylalanine called D-phenylalaline (DPA), reduces pain by decreasing the enzyme that breaks down endorphins. It is less clear whether DPA may help people with LBP, though there are a small number of reports to that effect, including one uncontrolled report of 27 of 37 people with LBP experiencing "good to excellent relief." In a double-blind trial, University of Texas researchers found that 250 mg of DPA four times per day for four weeks was no more effective than placebo for 30 people with various types of chronic pain; 13 of these people had low back pain. In a Japanese clinical trial, 4 grams of DPA per day was given to people with chronic low back pain half an hour before they received acupuncture. Although not statistically significant, the results were good or excellent for 18 of the 30. The most common supplemental form of phenylalanine is D,L-phenylalanine (DLPA). Doctors typically recommend 1,500-2,500 mg per day of DLPA.

2 Stars
Pain
1,500 mg daily
D-phenylalanine (DPA) decreases pain by blocking the enzymes that break down the body's natural painkillers. Clinical studies suggest DPA may inhibit some types of chronic pain.

Certain amino acids have been found to raise pain thresholds and increase tolerance to pain. One of these, a synthetic amino acid called D-phenylalanine (DPA), decreases pain by blocking the enzymes that break down endorphins and enkephalins, the body's natural pain-killing chemicals. DPA may also produce pain relief by other mechanisms, which are not well understood.

In animal studies, DPA decreased chronic pain within 15 minutes of administration and the effects lasted up to six days. It also decreased responses to acute pain. These findings have been independently verified in at least five other studies. Clinical studies on humans suggest DPA may inhibit some types of chronic pain, but it has little effect on most types of acute pain.

Most human research has tested the pain-relieving effects of 750 to 1,000 mg per day of DPA taken for several weeks of continuous or intermittent use. The results of this research have been mixed, with some trials reporting efficacy, others reporting no difference from placebo, and some reporting equivocal results. It appears that DPA may only work for some people, but a trial period of supplementation seems worthwhile for many types of chronic pain until more is known. If DPA is not available, a related product, D,L-phenylalanine (DLPA), may be substituted at amounts of 1,500 to 2,000 mg per day.

As early as 1981, preliminary human research showed that DPA made the pain-inhibiting effects of acupuncture stronger. One controlled animal study and two controlled trials in humans showed that DPA taken the day before acupuncture increased the effectiveness of acupuncture in reducing both acute dental and chronic low back pain.

2 Stars
Parkinson's Disease
Consult a qualified healthcare practitioner
In one trial, D-phenylalanine (DPA) supplementation improved motor control and tremors in people with Parkinson's disease. DPA should not be taken with L-dopa as it may interfere with the transport of L-dopa to the brain.

In a small, four-week trial, D-phenylalanine (DPA) supplementation improved motor control and tremors in people with Parkinson's disease. Additional research is needed before the benefits of this treatment can be considered proven. DPA should not be taken with L-dopa as it may interfere with the transport of L-dopa to the brain. People with Parkinson's disease should consult with a physician before using DPA. Some commercially available phenylalanine products contain a 50:50 mixture of DPA and LPA, the form of phenylalanine that occurs naturally in food (these products are known as DLPA). People with Parkinson's disease should consult a physician before using DPA or DLPA.

2 Stars
Vitiligo
50 mg daily per 2.2 lbs (1 kg) of body weight, with ultraviolet light exposure
L-phenylalanine, in conjunction with ultraviolet light exposure, may improve repigmentation of skin.

Supplementation with the amino acid L-phenylalanine (LPA) may have value when combined with ultraviolet (UVA) light therapy. Several clinical trials, including one double-blind trial, indicated that LPA (50 mg per 2.2 pounds of body weight per day-3,500 mg per day for a 154-pound person-or less) increased the extent of repigmentation induced by UVA therapy. LPA alone also produced a more modest repigmentation in some people. A study of vitiligo in children reported that LPA plus UVA was an effective treatment in a majority of the children.

A group of Spanish doctors reported on their experience using LPA over a six-year period. Some of the 171 people with vitiligo received LPA (50 or 100 mg per 2.2 pounds body weight per day) for up to three years. Between April and October of each year, participants also applied a 10% LPA gel, prior to exposing their skin to the sun for 30 minutes. Some improvement was seen in 83% of participants, and the results were rated as good in 57% (75% improvement or better).

1 Star
Alcohol Withdrawal (Glutamine, L-Tyrosine, Multivitamin, L-Tryptophan)
Refer to label instructions
In double-blind research, alcoholics treated with L-tyrosine combined with DLPA (D,L-phenylalanine), L-glutamine, prescription L-tryptophan, plus a multivitamin had reduced withdrawal symptoms and decreased stress.

Kenneth Blum and researchers at the University of Texas have examined neurotransmitter deficiencies in alcoholics. Neurotransmitters are the chemicals the body makes to allow nerve cells to pass messages (of pain, touch, thought, etc.) from cell to cell. Amino acids are the precursors of these neurotransmitters. In double-blind research, a group of alcoholics were treated with 1.5 grams of D,L-phenylalanine (DLPA), 900 mg of L-tyrosine, 300 mg of L-glutamine, and 400 mg of L-tryptophan (now available only by prescription) per day, plus a multivitamin-mineral supplement. This nutritional supplement regimen led to a significant reduction in withdrawal symptoms and decreased stress in alcoholics compared to the effects of placebo.

1 Star
Alcohol Withdrawal and Food Allergies
Refer to label instructions
In double-blind research, alcoholics treated with DLPA (D,L-phenylalanine) combined with L-tyrosine, L-glutamine, prescription L-tryptophan, plus a multivitamin had reduced withdrawal symptoms and decreased stress.

Kenneth Blum and researchers at the University of Texas have examined neurotransmitter deficiencies in alcoholics. Neurotransmitters are the chemicals the body makes to allow nerve cells to pass messages (of pain, touch, thought, etc.) from cell to cell. Amino acids are the precursors of these neurotransmitters. In double-blind research, a group of alcoholics were treated with 1.5 grams of D,L-phenylalanine (DLPA), 900 mg of L-tyrosine, 300 mg of L-glutamine, and 400 mg of L-tryptophan (now available only by prescription) per day, plus a multivitamin-mineral supplement. This nutritional supplement regimen led to a significant reduction in withdrawal symptoms and decreased stress in alcoholics compared to the effects of placebo.

1 Star
Osteoarthritis
Refer to label instructions
Supplementing with D-phenylalanine (DPA) has been shown to reduce chronic pain due to osteoarthritis. DPA inhibits the enzyme that breaks down some of the body's natural painkillers.

Supplementation with D-phenylalanine (DPA), a synthetic variation of the amino acid, L-phenylalanine (LPA), has reduced chronic pain due to osteoarthritis in a preliminary trial. In that study, participants took 250 mg three to four times per day, with pain relief beginning in four to five weeks. Other preliminary trials have confirmed the effect of DPA in chronic pain control, but a double-blind trial found no benefit. DPA inhibits the enzyme that breaks down some of the body's natural painkillers, substances called enkephalins, which are similar to endorphins. An increase in the amount of enkephalins may explain the reported pain-relieving effect of DPA. If DPA is not available, a related product, D,L-phenylalanine (DLPA), may be substituted (1,500 to 2,000 mg per day). Phenylalanine should be taken between meals, because protein found in food may compete for uptake of phenylalanine into the brain, potentially reducing its effect.

1 Star
Rheumatoid Arthritis
Refer to label instructions
D-phenylalanine has been used with mixed results to treat chronic pain, including pain caused by rheumatoid arthritis.

D-phenylalanine has been used with mixed results to treat chronic pain, including pain caused by RA. No research has evaluated the effectiveness of DL-phenylalanine, a related supplement, in treating people with RA. The effect of either form of phenylalanine in the treatment of people with RA remains unproven.

How It Works

How to Use It

DLPA has been used in amounts ranging from 75-1,500 mg per day. This compound can have powerful effects on mood and on the nervous system, and therefore DLPA should be taken only under medical supervision. LPA has been used in amounts up to 3.5 grams per day. For best results, phenylalanine should be taken between meals, because the protein present in food can interfere with the uptake of phenylalanine into the brain, potentially reducing its effect.

Where to Find It

LPA is found in most foods that contain protein. DPA does not normally occur in food. However, when phenylalanine is synthesized in the laboratory, half appears in the L-form and the other half in the D-form. These two compounds can also be synthesized individually, but it is more expensive to do so. The combination supplement (DLPA) is often used because of the lower cost and because both components exert different health-enhancing effects.

Possible Deficiencies

People whose diets are very low in protein may develop a deficiency of LPA, although this is believed to be very uncommon. However, one does not necessarily have to be deficient in LPA in order to benefit from a DLPA supplement.

Interactions

Interactions with Supplements, Foods, & Other Compounds

People with phenylketonuria must not supplement with phenylalanine.

Some research suggests that people with tardive dyskinesia may process phenylalanine abnormally. Until more is known, it makes sense for people with this condition to avoid phenylalanine supplementation.

LPA competes with several other amino acids for uptake into the body and the brain. Therefore, for best results, phenylalanine should be taken between meals, or away from protein-containing foods. People taking prescription or over-the-counter medications should consult a physician before taking DLPA.

Interactions with Medicines

As of the last update, we found no reported interactions between this supplement and medicines. It is possible that unknown interactions exist. If you take medication, always discuss the potential risks and benefits of adding a new supplement with your doctor or pharmacist.
The Drug-Nutrient Interactions table may not include every possible interaction. Taking medicines with meals, on an empty stomach, or with alcohol may influence their effects. For details, refer to the manufacturers' package information as these are not covered in this table. If you take medications, always discuss the potential risks and benefits of adding a supplement with your doctor or pharmacist.

Side Effects

Side Effects

The maximum amount of DLPA that is safe is unknown. However, consistent toxicity in healthy people has not been reported with 1,500 mg per day or less of DLPA, except for occasional nausea, heartburn, or transient headaches.

When 100 mg of LPA per 2.2 pounds body weight or more was given to animals, a variety of complex problems occurred, leading two researchers to have concerns about potential toxicity of high amounts in humans.1 While these concerns were directed at LPA specifically, they are likely to be equally applicable to DLPA. Although no serious adverse effects have been reported in humans taking phenylalanine, amounts greater than 1,500 mg per day should be supervised by a doctor.

References

1. Burkhart CG, Burkhart CN. Phenylalanine with UVA for the treatment of vitiligo needs more testing for possible side effects. J Am Acad Dermatol 1999;40:1015 [letter].