L-Histidine 60 capsL Histidine, provided by Douglas Laboratories, supplies 500 mg of the amino acid in each capsule. 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