L-Leucine

L-Leucine is one of the nine essential amino acids — those that humans cannot synthesise and must obtain through dietary protein. In its role as a food additive (E641), it functions primarily as a flavour modifier and anti-caking agent in powdered food products. As a flavour modifier it provides a mild bitter-savoury note and can influence the overall flavour perception of protein-containing foods and supplements. As an anti-caking agent it improves the flow properties of powdered formulations such as protein supplements, seasoning blends, and encapsulated flavour powders.

No specific JECFA ADI has been assigned to L-leucine as a food additive, reflecting its classification as a normal and essential dietary constituent. L-Leucine is a branched-chain amino acid involved in muscle protein synthesis and is produced naturally during digestion of all dietary proteins. The body handles leucine through well-characterised metabolic pathways with no accumulation or toxic threshold at food-relevant intake levels.

L-Leucine is approved in the EU as E641 for use in specific food applications, particularly in dietary supplements and powdered food products. Its dual function as both a flavour modifier and anti-caking agent makes it efficient in formulations that benefit from both properties simultaneously. Consumers who follow protein supplementation regimes may encounter leucine both as an additive (E641) and as a nutritionally declared amino acid on supplement labels — these are chemically the same compound. No adverse effects from food additive use of L-leucine have been reported, and it is well tolerated by the general population.