{"ok":true,"entry":{"slug":"leucine","kind":"supplement","name":"leucine","aliases":["L-leucine"],"brands_sg":["California Gold Nutrition","MuscleTech","Nutricost","Swanson Vitamins","Super Nutrition"],"class":"branched-chain amino acid","tags":["fitness"],"use_for":"signals muscle protein synthesis · not a solo supplement","use_after":"spread across meals · 1–3 g per meal in issn's stand","use_duration":null,"take_with":"a complete protein — leucine alone lacks the other eaas","pros":["issn: 1–3 g per meal appears to trigger translation","ods: leucine might stimulate synthesis in worked muscle","safe limit near 500 mg/kg a day in study populations"],"cons":["ods: single amino acids have not consistently helped","issn: leucine on its own is not the way to supplement","whey carries more leucine than casein or soy already"],"dose_note":"issn's stand puts 700–3000 mg of leucine inside each 20–40 g protein dose, or roughly 1–3 g per meal; nih ods cites an upper safe limit near 500 mg/kg a day — about 38 g for a 75 kg man — from studies in healthy young and elderly men","dosage":{"ul":null,"unit":"g","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":["beyond about 500 mg/kg a day the safety data stop","not listed in hsa annex a or b (oct 2025) — not a clearance"],"clashes":[],"sources":[{"id":"ods_ex_bcaa_mps","url":"https://ods.od.nih.gov/factsheets/ExerciseAndAthleticPerformance-HealthProfessional/","label":"NIH ODS — Exercise and Athletic Performance (HP), BCAA section","quote":"The BCAAs, especially leucine, might also stimulate protein synthesis in exercised muscle","accessed":"2026-08-27"},{"id":"ods_ex_bcaa_single","url":"https://ods.od.nih.gov/factsheets/ExerciseAndAthleticPerformance-HealthProfessional/","label":"NIH ODS — Exercise and Athletic Performance (HP), BCAA implications for use","quote":"Studies have not consistently shown that taking supplements of BCAAs or any of their three constituent amino acids singly enhances exercise and athletic performance, builds muscle mass, or aids in recovery from exercise","accessed":"2026-08-27"},{"id":"ods_ex_leucine_safety","url":"https://ods.od.nih.gov/factsheets/ExerciseAndAthleticPerformance-HealthProfessional/","label":"NIH ODS — Exercise and Athletic Performance (HP), BCAA safety","quote":"For leucine alone, studies suggest an upper safe limit of intake of 500 mg/kg per day in healthy young and elderly men, or about 38 g/day for a man weighing 75 kg","accessed":"2026-08-27"},{"id":"ods_ex_whey_leucine","url":"https://ods.od.nih.gov/factsheets/ExerciseAndAthleticPerformance-HealthProfessional/","label":"NIH ODS — Exercise and Athletic Performance (HP), protein powders and BCAAs","quote":"protein powders made from complete proteins, especially whey, which has more leucine than either casein or soy","accessed":"2026-08-27"},{"id":"issn_leucine_dose","url":"https://www.ebi.ac.uk/europepmc/webservices/rest/PMC5477153/fullTextXML","label":"ISSN position stand: protein and exercise (Jäger et al., JISSN 2017) — position statement 5","quote":"Acute protein doses should strive to contain 700–3000 mg of leucine and/or a higher relative leucine content, in addition to a balanced array of the essential amino acids (EAAs)","accessed":"2026-08-27"},{"id":"issn_leucine_meal","url":"https://www.ebi.ac.uk/europepmc/webservices/rest/PMC5477153/fullTextXML","label":"Jäger et al., JISSN 2017 — amino acid summary","quote":"In addition, doses of approximately one to three g of leucine per meal appear to be needed to stimulate protein translation machinery","accessed":"2026-08-27"},{"id":"issn_leucine_alone","url":"https://www.ebi.ac.uk/europepmc/webservices/rest/PMC5477153/fullTextXML","label":"Jäger et al., JISSN 2017 — leucine section","quote":"Even though leucine has been demonstrated to independently stimulate protein synthesis, it is important to recognize that supplementation should not be with just leucine alone","accessed":"2026-08-27"},{"id":"issn_leucine_eaa","url":"https://www.ebi.ac.uk/europepmc/webservices/rest/PMC5477153/fullTextXML","label":"Jäger et al., JISSN 2017 — leucine and total EAA dose","quote":"increasing leucine concentration may stimulate increases in muscle protein, but a higher total dose of all EAAs (as free form amino acids or intact protein sources) seems to be most suited for sustaining the increased rates of MPS","accessed":"2026-08-27"},{"id":"hsa_restricted","url":"https://file.go.gov.sg/hsa-chp-prohibited-restricted-ing-guidelines.pdf","label":"HSA — Guidelines on Prohibited and Restricted Ingredients in Health Supplements and Traditional Medicines, GL-CHPB-1-012 Rev 001 (Oct 2025), Annexes A/B","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-leucine","label":"iHerb Singapore — Leucine category page, default sort","quote":"Leucine: BCAA Powder for Muscle Growth & Recovery | iHerb … 1 - 24 of 24 results","accessed":"2026-08-27"}],"brand_certs":null,"updated_at":"2026-08-29T16:16:23.779398+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."}