{"ok":true,"entry":{"slug":"phenylalanine","kind":"supplement","name":"phenylalanine","aliases":["DL-phenylalanine","DLPA","L-phenylalanine"],"brands_sg":["Life Extension","NOW Foods","Swanson","Vitacost","Source Naturals"],"class":"amino acid","tags":["general"],"use_for":"the body converts it to tyrosine · few human trials","use_after":null,"use_duration":null,"take_with":null,"pros":["the body's route from phenylalanine to tyrosine","not listed in hsa's prohibited or restricted annexes"],"cons":["phenylketonuria — a lifelong phe-restricted diet","no human supplement rct surfaced in a 274-hit search","the human literature is about pku, not supplements"],"dose_note":"no supplement dose could be sourced: the human phenylalanine literature searched is dominated by phenylketonuria dietary management, and the DL-phenylalanine hits are chemistry, materials and animal work rather than supplementation trials","dosage":{"ul":null,"unit":"mg","fda_dv":null,"rda_ai":null,"ul_status":"none_established","population":"general adult","hsa_max_daily":null},"ul_status":"none_established","sg_class":null,"cautions":["phenylketonuria — the treatment is a lifelong phenylalanine-restricted diet, which a phenylalanine supplement runs against","excess phenylalanine competitively blocks some other amino acids from entering the brain"],"clashes":[],"sources":[{"id":"pku_pet2026","url":"https://europepmc.org/article/MED/42361219","label":"Positron Emission Tomography (PET) in Phenylketonuria: A Systematic Review of Brain Metabolism Beyond Phenylalanine (Am J Med Genet A 2026; PMID 42361219)","quote":"PKU impairs the conversion of Phe to tyrosine and causes excess phenylalanine to accumulate. This accumulation can competitively block some other amino acids from entering the brain.","accessed":"2026-08-27"},{"id":"pku_pet2026_nt","url":"https://europepmc.org/article/MED/42361219","label":"PET in Phenylketonuria systematic review (Am J Med Genet A 2026) — neurotransmitters","quote":"This may reduce production of key neurotransmitters like dopamine and serotonin, which can affect brain function and development.","accessed":"2026-08-27"},{"id":"rondanelli2023","url":"https://europepmc.org/article/MED/37001196","label":"A food pyramid for adult patients with phenylketonuria and a systematic review on the optimal dietary treatment of adult patients with PKU (Rondanelli et al., Clin Nutr 2023; PMID 37001196)","quote":"Early dietary treatment is mind-saving in patients with phenylketonuria. A \"diet-for-life\" is advocated, aimed to prevent effects of chronic exposure to hyperphenylalaninemia.","accessed":"2026-08-27"},{"id":"epmc_phe_search","url":"https://www.ebi.ac.uk/europepmc/webservices/rest/search?query=(TITLE:%22phenylalanine%22)%20AND%20(TITLE:%22supplementation%22%20OR%20TITLE:%22requirement%22%20OR%20TITLE:%22safety%22%20OR%20TITLE:%22phenylketonuria%22)%20AND%20(SRC:%22MED%22)&format=json&resultType=core","label":"Europe PMC REST search, 27 Aug 26 — phenylalanine in title plus supplementation/requirement/safety/phenylketonuria (774 hits, PKU-dominated; no human supplementation trial in the first page of results)","quote":"\"hitCount\":774 … \"Is Phenylalanine Restricted Dietary Treatment in Phenylketonuria Associated with Disordered Eating: A Systematic Review.\"","accessed":"2026-08-27"},{"id":"epmc_dlpa_search","url":"https://www.ebi.ac.uk/europepmc/webservices/rest/search?query=(TITLE:%22DL-phenylalanine%22%20OR%20TITLE:%22D-phenylalanine%22%20OR%20TITLE:%22phenylalanine%20supplementation%22)&format=json&resultType=core","label":"Europe PMC REST search, 27 Aug 26 — DL-phenylalanine / D-phenylalanine / phenylalanine supplementation in title (274 hits; the results are synthesis chemistry, biosensors, nanomaterials and rodent work, not human supplementation trials)","quote":"\"hitCount\":274 … \"Site-specifically immobilized D-amino acid dehydrogenase for the synthesis of D-phenylalanine\" … \"Neuroprotective Potential of Chromium-D-Phenylalanine … Rotenone-Induced Parkinsonism in Rats\"","accessed":"2026-08-27"},{"id":"hsa_hs_defn","url":"https://file.go.gov.sg/hsa-hs-guidelines.pdf","label":"HSA Health Supplements Guidelines GL-CHPB-3-001 Rev. No. 020 (January 2026) — s3.1 working definition and clause 4.8 (Tables 4-5 cover vitamins and minerals only)","quote":"Vitamins, minerals, amino acids, fatty acids, enzymes, probiotics and other bioactive substances … HS for use by the general adult population should not contain vitamins and minerals exceeding the stipulated limits stated in Tables 4 and 5.","accessed":"2026-08-27"},{"id":"hsa_pr_notlisted","url":"https://file.go.gov.sg/hsa-chp-prohibited-restricted-ing-guidelines.pdf","label":"HSA Guidelines on Prohibited and Restricted Ingredients in HS and TM, GL-CHPB-1-012 Rev. No. 001 (Oct 2025), Annex A/B — full text searched 27 Aug 26, no row for phenylalanine","quote":"The objective of this guideline is to highlight the substances of concern when used in HS and TM and is not meant to be an exhaustive list.","accessed":"2026-08-27"},{"id":"iherb_sg","url":"https://sg.iherb.com/c/l-phenylalanine","label":"iHerb Singapore category page \"L-Phenylalanine Supplements\", default best-selling order, first 5 distinct brands","quote":"L-Phenylalanine Supplements","accessed":"2026-08-27"}],"brand_certs":null,"updated_at":"2026-08-29T16:16:27.496708+08:00"},"disclaimer":"kozen-x is not a medical device and does not give medical advice. it lists what published sources have written down. absence of a record is not the same as safe."}