Limited evidenceStress & mood

DLPA (DL-Phenylalanine)

DLPA is a 50/50 racemic mix of L-phenylalanine (a dietary amino acid) and D-phenylalanine (a synthetic isomer claimed to block enkephalin breakdown and relieve chronic pain). The pain evidence is old and largely negative; the mood evidence rests on one 1979 trial versus imipramine with no placebo arm.

What the science says

D-phenylalanine failed to relieve chronic pain in a controlled crossover trial Limited evidence
The enkephalinase-inhibition theory predicts that D-phenylalanine prolongs endogenous opioid action. Walsh's 1986 double-blind crossover trial in chronic pain patients tested 250 mg D-phenylalanine four times daily and found no significant analgesic effect versus placebo on any pain measure. Small Japanese studies reported that D-phenylalanine enhanced acupuncture analgesia, but these were uncontrolled or partially controlled and have not been replicated.
The antidepressant claim comes from a 1979 active-comparator study with no placebo group Limited evidence
Beckmann's double-blind study compared DL-phenylalanine 150-200 mg/day against imipramine 150-200 mg/day in depressed inpatients over 30 days and reported comparable improvement in both arms. Without a placebo arm, equivalence to an antidepressant in a small short trial cannot establish efficacy — depression trials routinely show 30-40% placebo response. No placebo-controlled replication has been published in the four decades since.
Not better than plain L-phenylalanine for anything demonstrated Limited evidence
Half of a DLPA capsule is ordinary L-phenylalanine, which the body uses normally; the D-isomer is not incorporated into protein and is largely excreted or slowly converted. Because the D-isomer's proposed unique benefit (analgesia) is the claim that failed in controlled testing, the premium over L-phenylalanine buys an ingredient with no proven advantage.

Dosage & safety

Studied doseTrials used 250 mg D-phenylalanine four times daily (1 g/day) for pain and 150-200 mg/day DLPA for depression. Commercial DLPA capsules are usually 500-750 mg, taken 1-3 times daily on an empty stomach — well above the doses in the depression trial and in a range never tested against placebo for pain.

SafetySame absolute contraindication as L-phenylalanine: never use in phenylketonuria. Do not combine with MAO inhibitors — risk of hypertensive reaction. Reported side effects include heartburn, nausea, headache, insomnia and anxiety; higher doses may raise blood pressure. Caution with antipsychotics, in pregnancy and breastfeeding (unstudied), and with existing hypertension or anxiety disorders. DLPA is sometimes marketed for opioid withdrawal — there is no controlled evidence for this and it should not replace medical management. Not banned in sport.

Scientific references

Analgesic effectiveness of D-phenylalanine in chronic pain patients
Walsh NE et al — Arch Phys Med Rehabil, 1986
DL-phenylalanine versus imipramine: a double-blind controlled study
Beckmann H et al — Arch Psychiatr Nervenkr (1970), 1979

Where to buy

Source Naturals, DLPA, 120 Tablets

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