L-Leucine 500mg, 240 Capsules, Source NaturalsL Leucine Energy Support L Leucine is an essential amino acid, specifically classified as a "branched chain amino acid" (BCAA). BCAA's, 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. Supplement Facts for 500 mg Serving Size: 3 capsules Amount %DV Calories 5 L Leucine 1. 5