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.
Where are they found?
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.
Phenylalanine has been
used in connection with the following conditions (refer to the
individual health concern for complete information):
and relatively consistent scientific data showing a substantial health benefit.
Contradictory, insufficient, or preliminary studies
suggesting a health benefit or minimal health benefit.
For an herb, supported by traditional use but minimal
or no scientific evidence. For a supplement, little scientific support and/or minimal health
Who is likely to be deficient?
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.
How much is usually taken?
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
Are there any side effects or interactions?
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.
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.
At the time of writing, there were no well-known drug interactions
References (To view, roll mouse over the "References" heading; to hide, click on the heading)
1. Burkhart CG, Burkhart CN. Phenylalanine with UVA for the treatment of
vitiligo needs more testing for possible side effects. J Am Acad Dermatol
The information presented in Aisle7 is for informational purposes only.
It is based on scientific studies (human, animal, or in vitro), clinical experience,
or traditional usage as cited in each article. The results reported may not necessarily occur
in all individuals. For many of the conditions discussed, treatment with prescription or over
the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist
for any health problem and before using any supplements or before making any changes in