L-Leucine
The short version
An essential branched-chain amino acid — used as a tabletting lubricant and a sweetness modifier.
It's widely considered safe at the amounts used in food, so we mark it green. The Safety section below has the details.
Safety profile
JECFA (2004) found no safety concern at current levels of intake when used as a flavouring agent, noting it is a macronutrient and a normal component of dietary protein; it did not set an ADI. Dietary additions metabolized identically to protein-derived leucine. Pharmacological supplement doses are sometimes restricted in clinical maple-syrup-urine-disease patients (a rare inborn error of metabolism).
Sources
- Commission Regulation (EU) 2015/649 — use of L-leucine (E 641) as a carrier for table-top sweeteners in tablets — Publications Office of the European Union, 2015. EU authorisation limited to table-top sweeteners in tablets, 50 000 mg/kg
- JECFA — L-Leucine (flavouring agent No. 1423), evaluation 2004 — Joint FAO/WHO Expert Committee on Food Additives (WHO), 2004. Safety: no concern as flavouring; normal protein component
- 21 CFR 172.320 — Amino acids (nutrients added to foods) — U.S. eCFR (Office of the Federal Register), 2026. US: permitted as a nutrient added to foods
Checked against these sources on .
Educational information only. Not medical, dietary or veterinary advice. Spotted an error? Tell us.