Phenylalanine
Research reviewed: Up until 03/2026
Phenylalanine is a dietary supplement with 8 published peer-reviewed studies involving 237 participants, researched for Depression & Mood, Pain Relief, Skin Conditions.
Evidence at a Glance
Strength is scored by study design, sample size, study type, and outcomes
Depression & Mood
ModeratePain Relief
StrongSkin Conditions
ModerateResearch Visualised
Visual breakdown of the clinical data.
Study Quality Breakdown
What types of studies were conducted
Participants Per Study
Larger samples = more reliable results
Research Timeline
When the studies were published
All Studies
Detailed breakdown of each trial. Click to expand.
Depression & Mood
To evaluate D-phenylalanine (DPA) as antidepressant
Study Type
Randomised, double-blind, controlled
Purpose
To evaluate D-phenylalanine (DPA) as antidepressant
Dose
75-200 mg/day D-phenylalanine
Participants
40 patients with depression
Duration
20 days
Results
Significant antidepressant effects with DPA comparable to imipramine in HAM-D scores. Rapid onset within 2 weeks. Proposed mechanism via enkephalin protection.
How They Measured It
Hamilton Depression Rating Scale, clinical assessment
To compare DL-phenylalanine with imipramine for depression
Study Type
Randomised, controlled trial
Purpose
To compare DL-phenylalanine with imipramine for depression
Dose
150-200 mg/day DL-phenylalanine
Participants
27 depressed patients
Duration
30 days
Results
DL-phenylalanine produced comparable antidepressant effects to imipramine with fewer side effects. Both groups showed significant HAM-D improvement. Phenylalanine well-tolerated.
How They Measured It
Hamilton Depression Scale, Zung Self-Rating Scale
To evaluate L-phenylalanine as augmentation for antidepressant treatment
Study Type
Open-label clinical study
Purpose
To evaluate L-phenylalanine as augmentation for antidepressant treatment
Dose
1000-3000 mg/day L-phenylalanine
Participants
23 treatment-resistant depression patients
Duration
3 weeks
Results
Significant response in 74% of patients with combination therapy. Rapid improvement in mood, energy, and motivation. L-phenylalanine conversion to tyrosine and dopamine proposed mechanism.
How They Measured It
HAM-D, BDI, CGI
Pain Relief
To evaluate DL-phenylalanine (DLPA) for chronic pain conditions
Study Type
Randomised, double-blind, placebo-controlled
Purpose
To evaluate DL-phenylalanine (DLPA) for chronic pain conditions
Dose
250 mg DLPA four times daily
Participants
43 patients with chronic pain
Duration
4 weeks
Results
Significant reduction in pain scores (p<0.001) vs placebo. Analgesic consumption reduced by 45%. Functional status improved. Enkephalin-sparing mechanism proposed.
How They Measured It
Pain VAS, analgesic use, functional impairment
To assess D-phenylalanine on dental pain and analgesic requirements
Study Type
Randomised, placebo-controlled
Purpose
To assess D-phenylalanine on dental pain and analgesic requirements
Dose
250 mg DPA before dental procedure
Participants
29 dental patients
Duration
Acute peri-procedure study
Results
DPA significantly reduced post-procedural pain scores (p=0.04) and analgesic requirements. Pain suppression lasted 4-6 hours. Endorphin-protecting mechanism confirmed.
How They Measured It
Post-procedural pain VAS, analgesic requirements
Skin Conditions
To evaluate L-phenylalanine with UVA radiation for vitiligo treatment
Study Type
Randomised, controlled trial
Purpose
To evaluate L-phenylalanine with UVA radiation for vitiligo treatment
Dose
50-100 mg/kg/day L-phenylalanine + UVA
Participants
45 vitiligo patients
Duration
6 months
Results
Significant repigmentation in 69% of patients receiving L-phenylalanine + UVA vs 28% UVA alone (p<0.001). Enhanced melanin synthesis confirmed.
How They Measured It
Repigmentation assessment, skin melanin content
To assess L-phenylalanine on attention and cognitive performance in adults with ADHD
Study Type
Randomised, double-blind, placebo-controlled
Purpose
To assess L-phenylalanine on attention and cognitive performance in adults with ADHD
Dose
1500 mg/day L-phenylalanine
Participants
30 adults with ADHD
Duration
4 weeks
Results
Significant improvements in attention and reduced inattention scores (p=0.03) vs placebo. Cognitive performance on CPT improved. Catecholamine synthesis as proposed mechanism.
How They Measured It
ADHD symptom scale, Conners' CPT, sustained attention
To review the clinical evidence for DL-phenylalanine in depression and pain
Study Type
Systematic review
Purpose
To review the clinical evidence for DL-phenylalanine in depression and pain
Dose
Various
Participants
Systematic review
Duration
Various
Results
Evidence supports antidepressant and analgesic effects of DLPA. Mechanism via catecholamine and enkephalin pathways. Older studies but effect size notable. More modern large RCTs needed.
How They Measured It
Systematic review of clinical trials
Frequently Asked Questions
Common questions about Phenylalanine research
There are currently 8 peer-reviewed studies on Phenylalanine (Phenylalanine), involving 237 total participants. Research covers Mood enhancement, Pain relief, Depression and 1 more areas. The overall evidence strength is rated as Strong.
The evidence is currently rated as "Strong Evidence". This rating is based on study design quality (randomisation, blinding, placebo controls), sample sizes, study types (7 human studies), and reported outcomes.
Phenylalanine has been researched for: Mood enhancement, Pain relief, Depression, Attention & focus. Each area has its own body of evidence which you can explore in the study breakdowns above.
Yes, 7 out of 8 studies are human trials. Human trials carry more weight in our evidence scoring system.
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