About
What it is and where it shows up.
L-leucine is an essential branched-chain amino acid (BCAA) that cannot be synthesised by the human body and must be obtained through diet. It is added to foods, infant formulae, dietary supplements, and sports nutrition products to supplement protein quality and support muscle protein synthesis.
Safety summary
The regulatory and scientific consensus.
L-leucine is well-tolerated at normal dietary intakes; no formal ADI has been established by JECFA or EFSA for human food use, reflecting its status as a natural dietary constituent. High supplemental doses may disturb the balance of other branched-chain and essential amino acids, and excessive isolated leucine intake has been associated with pellagra-like symptoms in animal studies. No IARC carcinogenicity classification exists; the ingredient is broadly considered safe for the general adult population at food-additive use levels.
Regulatory landscape
What food-safety regulators have decided.
| Jurisdiction | Status | Note |
|---|---|---|
| FSANZ (Food Standards Australia New Zealand) (Australia) | Approved | Permitted as a food additive and nutritive substance under the Australia New Zealand Food Standards Code; no specific numeric limit established for general food use.source |
| EFSA (European Food Safety Authority) (European Union) | Approved | Commission Regulation (EU) 2020/378 authorises L-leucine (produced by E. coli NITE BP-02351) as a feed nutritional additive and sensory flavouring for all animal species. As a human food ingredient, L-leucine (E641) is permitted as a flavour enhancer under Regulation (EC) No 1333/2008; no numeric ADI established for human food use. EFSA NDA Panel assessed health claims related to L-leucine in 2014.source |
| FSSAI (Food Safety and Standards Authority of India) (India) | Approved | Permitted as an amino acid ingredient under the Food Safety and Standards (Health Supplements, Nutraceuticals, Food for Special Dietary Use, Food for Special Medical Purpose, Functional Food and Novel Food) Regulations, 2016, Schedule I. Suitable esters, derivatives, isomers and salts of amino acids may be used with written notification to the Food Authority.source |
| FDA (Food and Drug Administration) (United States) | Approved | Listed in FDA's Substances Added to Food (formerly EAFUS) inventory as GRAS; regulated under 21 CFR 172.320 as a direct food additive (amino acid) for nutritional purposes with GMP-level use limits. |
Who should approach with care
Whose guidance would steer them away.
Phenylketonuria — Individuals with phenylketonuria (PKU) or other inborn errors of amino-acid metabolism (e.g., isovaleric acidaemia, maple syrup urine disease) may be unable to metabolise branched-chain amino acids including L-leucine normally, requiring medical supervision of intake.
Kidney Disease — High supplemental amino acid loads, including L-leucine, may increase nitrogenous waste and exacerbate impaired renal clearance in patients with chronic kidney disease; medical guidance is recommended before use of concentrated supplements.
Liver Disease — Amino acid metabolism is substantially hepatic; patients with significant liver disease or hepatic encephalopathy should seek medical advice before consuming high-dose amino acid supplements containing L-leucine.
Infants — Infant formulae containing added L-leucine should conform to regulatory compositional limits (e.g., FSSAI Infant Formula Regulations, EU Regulation 609/2013); excess isolated leucine supplementation in infants has not been adequately studied and should only be used under medical supervision.
Research citations
The sources behind this verdict.
- 1FDA. Substances Added to Food – L-leucine entry (formerly EAFUS). hfpappexternal.fda.gov
- 2FSSAI. Food Safety and Standards (Health Supplements, Nutraceuticals …) Regulations – Compendium (2021), 2021. fssai.gov.in
- 3other. Commission Regulation (EU) 2020/378 of 5 March 2020 concerning the authorisation of L-leucine as a feed additive for all animal species, 2020. eur-lex.europa.eu
- 4EFSA. Safety and efficacy of l-leucine produced by fermentation with Escherichia coli NITE BP-02351 for all animal species, 2019. efsa.europa.eu
- 5PubMed. Leucine supplementation and intensive training (Norton & Layman, 2006, Am J Clin Nutr), 2006. pubmed.ncbi.nlm.nih.gov
Independently researched5 citations