L-Arginine 100 CapsL Arginine capsules, provided by Douglas Laboratories, contain 700 mg pure, crystalline L arginine. FUNCTIONS Amino acids have many functions in the body. They are the building blocks for all body proteinsstructural proteins that build muscle, connective tissues, bones and other structures, and functional proteins in the form of thousands of metabolically active enzymes. Amino acids provide the body with the nitrogen that is essential for growth and