From the Manufacturer's Label:
L-Leucine is an essential amino acid, specifically classified as a "branched-chain amino acid" (BCAA). BCAAs, especially leucine, stimulate muscle protein synthesis and may be the major fuel involved in anabolic reactions. This makes them especially important for body builders and other athletes in sports that demand explosive strength.**
Contains no yeast, dairy, egg, gluten, corn, soy or wheat. Contains no sugar, starch, salt, preservatives, or artificial color, flavor or fragrance.