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evidence · mechanism · dose
Supplements/Amino Acid

L-Phenylalanine

Precursor to tyrosine and catecholamines.

Mood & AnxietyBrain & Cognitive

Overview

Precursor to tyrosine and catecholamines.

Natural sources
    Common forms

      Mechanism of action

      Hydroxylated to tyrosine; mood-elevating.

      Pathways

        Effects on the body

        Organ system effects

        Evidence-based benefits

        May help depression

        Moderate evidence

        Potential side effects

        Common
        • · Headache
        • · Anxiety
        Rare
          Serious

            Drug interactions

            No notable interactions reported.

            Supplement interactions

            Pairs well with

            None listed.

            Avoid combining with

            No specific avoidances listed.

            Dosing & bioavailability

            Typical dose
            500–1500 mg

            Where to buy

            Affiliate-style search links to reputable retailers. We don't endorse specific brands — verify third-party testing (USP, NSF, Informed Sport) before purchase.

            Amino Acid
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            Amino Acid
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            Thorne
            Practitioner-grade · NSF tested

            Scientific evidence (8)

            RCTJ Clin Psychiatry · 1986

            Phenylalanine in depression

            Sabelli HC, et al.

            155 depressed patients

            Key findings

            Significant improvement in 31 of 40 patients.

            Open study
            Systematic reviewPubMed (NLM) · 1970

            PubMed: L-Phenylalanine — May help depression

            Live PubMed search

            Live results for "L-Phenylalanine May help depression" across the PubMed/MEDLINE peer-reviewed index.

            Key findings

            Opens current human and preclinical literature matching L-Phenylalanine and "May help depression". Filter by RCT, meta-analysis, or year on the results page.

            Open study
            Systematic reviewPubMed (NLM) · 1970

            PubMed: L-Phenylalanine — randomized controlled trial

            Live PubMed search

            Live results for "L-Phenylalanine randomized controlled trial" across the PubMed/MEDLINE peer-reviewed index.

            Key findings

            Opens current human and preclinical literature matching L-Phenylalanine and "randomized controlled trial". Filter by RCT, meta-analysis, or year on the results page.

            Open study
            Systematic reviewPubMed (NLM) · 1970

            PubMed: L-Phenylalanine — meta-analysis

            Live PubMed search

            Live results for "L-Phenylalanine meta-analysis" across the PubMed/MEDLINE peer-reviewed index.

            Key findings

            Opens current human and preclinical literature matching L-Phenylalanine and "meta-analysis". Filter by RCT, meta-analysis, or year on the results page.

            Open study
            Systematic reviewPubMed (NLM) · 1970

            PubMed: L-Phenylalanine — pharmacokinetics

            Live PubMed search

            Live results for "L-Phenylalanine pharmacokinetics" across the PubMed/MEDLINE peer-reviewed index.

            Key findings

            Opens current human and preclinical literature matching L-Phenylalanine and "pharmacokinetics". Filter by RCT, meta-analysis, or year on the results page.

            Open study
            Systematic reviewPubMed (NLM) · 1970

            PubMed: L-Phenylalanine — safety adverse events

            Live PubMed search

            Live results for "L-Phenylalanine safety adverse events" across the PubMed/MEDLINE peer-reviewed index.

            Key findings

            Opens current human and preclinical literature matching L-Phenylalanine and "safety adverse events". Filter by RCT, meta-analysis, or year on the results page.

            Open study
            Systematic reviewPubMed (NLM) · 1970

            PubMed: L-Phenylalanine — dose response

            Live PubMed search

            Live results for "L-Phenylalanine dose response" across the PubMed/MEDLINE peer-reviewed index.

            Key findings

            Opens current human and preclinical literature matching L-Phenylalanine and "dose response". Filter by RCT, meta-analysis, or year on the results page.

            Open study
            Systematic reviewGoogle Scholar · 1970

            Google Scholar: L-Phenylalanine — clinical evidence

            Live Scholar search

            Cross-database citation index for L-Phenylalanine as it relates to "clinical evidence".

            Key findings

            Includes preprints, theses, and journal articles. Useful for tracking citation counts and follow-on work.

            Open study
            Educational use only. This profile is not medical advice. Consult a qualified healthcare professional before starting any supplement, especially if you take prescription medication or have a chronic condition.