L-Phenylalanine: Overview

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

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D-phenylalanine (DPA) is not normally found in the body and cannot be converted to L-tyrosine, L-dopa, or norepinephrine.  As a result, DPA is converted primarily to phenylethylamine (a potential mood elevator).  DPA also appears to influence certain chemicals in the brain that relate to pain sensation.


DLPA is a mixture of the essential amino acid LPA and its mirror image DPA.  LPA is found in most foods that contain protein.  DPA does not normally occur in food, but when synthesized in the laboratory, half appears as LPA and half as DPA.  The combination supplement (DLPA) is often used because both components exert different health-enhancing effects.

Why it is Recommended

Although rare, individuals whose diets are very low in protein may develop a deficiency of L-phenylalanine.  Benefits of supplementation are typically achieved in the absence of an outright deficiency.

L-Phenylalanine promotes alertness; reduces hunger pangs; improves memory; antidepressant; helps in controlling pain, particularly arthritis; used to help treat Parkinson's disease; alleviates PMS symptoms.  Should not be taken by diabetics, anyone suffering from anxiety attacks, high blood pressure, PKU or melanoma.


DLPA has been used in amounts ranging from 75 to 1,500mg per day.

Side-Effects; Counter-Indicators and Warnings

Consistent toxicity in healthy people has not been reported with 1,500mg per day or less of DLPA, except for occasional nausea, heartburn, or transient headaches.

Since DLPA competes with other amino acids for attachment on a common amino acid carrier in the body, it should not be taken with protein containing foods.  Individuals taking prescription or over-the-counter medications should consult a physician before taking DLPA.

This compound can have powerful effects on mood and on the nervous system, and therefore DLPA should be taken only under medical supervision.

People with phenylketonuria must not supplement phenylalanine.  Some research suggests that tardive dyskinesia patients may process phenylalanine abnormally.  Until more is known, it makes sense for people with this condition to avoid phenylalanine supplementation.

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L-Phenylalanine can help with the following:


Parkinson's Disease

D-phenylalanine (DPA) may be helpful for some individuals with Parkinson's disease. [Arzneimittelforsch 26: pp.577-9, 1976]



A recommended dosage is usually 2 to 3gm daily, depending on the severity of the vitiligo.  For best absorption, L-phenylalanine should be taken in between meals.



Phenylalanine can affect depression via three separate pathways.

  1. D-phenylalanine (DPA) exerts antidepressant activity due to its metabolism to phenylethylamine (PEA).
  2. DPA inhibits the breakdown of the body's endogenous opiates thus producing a state of euphoria.
  3. Phenylalanine is an important precursor for the production of noradrenaline and adrenaline thus increasing the body's ability to cope with stress.

A number of double-blind clinical trials have demonstrated that dosages of DLPA, the form commonly found in supplements, at doses as low as 150mg per day is effective in the treatment of some forms of depression.


Rheumatoid Arthritis

The 'D' form of phenylalanine (DPA) has been used to treat chronic pain, including rheumatoid arthritis, with mixed effectiveness.


D-phenylalanine (DPA) has been used to treat the chronic pain of osteoarthritis with both positive and negative results.

Neck / Spine

Low Back Pain

The brain responds to pain signals by producing and activating morphine-like hormones called endorphins.  This pain relief effect lasts for about 30 hours (longer than known analgesics), and without side-effects when given frequently.  It was discovered that d- and dl-Phenylalanine (DLPA), but not l-Phenylalanine, inhibit several of the enzymes responsible for endorphin destruction.  DLPA appears to restore endorphin levels to a normal range, while simultaneously producing a reduction in pain.  It often equals or exceeds morphine or other opiate derivatives in its effect and is non-addictive.  Start with 500mg qd and work up to 3-4gm qd.  This is a precursor for epinephrine and phenylethylamine (PEA).  PEA has amphetamine-like stimulant properties.  Chocolate contains high levels of PEA.

Tumors, Malignant

Not recommended for

Cancer patients, such as those with melanoma, should avoid taking L-phenylalanine and/or Tyrosine as these may stimulate the growth of such cancers.

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May be useful: may help with
May be useful:
may help with
Moderately useful: often helps with
Moderately useful:
often helps with
Should be avoided: is NOT recommended for
Should be avoided:
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