Leucine is an essential amino acid, which means our bodies cannot produce leucine by itself but have to be taken as diet. Human dietary sources are foods that contain protein, such as meats, dairy products, soy products, and beans and other legumes It is used in the biosynthesis of protein. It is a branched chain amino acid containing an α-amino acid, an α-carboxylic acid and a side chain isobutyl group. It is represented by its E number as E641 under food additives.
In an industrial scale, L-leucine can be prepared by culturing in a medium a microorganism belonging to the genus Escherichia and having resistance to a leucine analogue and an ability to produce L-leucine, allowing L-leucine to accumulate in the culture, recovering L-leucine therefrom.
However, leucine can be found naturally in cheese, soybeans, beef, chicken, nuts, fish, beans etc. The recommended intake for leucine is 39 mg per kilogram of body weight.
L-leucine is used as a food flavouring agent and as a dietary supplement widely. Studies have revealed that this amino acid acts in a unique way: unlike other amino acids, it aids in burning fat without burning a muscle by sparing the muscle proteins and leaving them to assist in building and in increasing the muscle gain and mass. Researches confirmed that people staying on the protein-rich diet, which includes enough of Leucine, lose more body fat while retaining a more lean muscle mass.
L-leucine is used nutritional therapy in pharmaceutical industry. It is used as a fragrance ingredient in shampoos, hair conditioners, creams, lotions etc.