Amino acids have many functions in the body. They are the building blocks for all body proteins—structural 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 maintenance of all tissues and structures. Aside from these general functions, individual amino acids also have specific functions in many aspects of human physiology and biochemistry. Amino acids serve as precursors for many nitrogenous substances. These include heme, purines, pyrimidines, hormones, and neuro-transmitters, including biologically active peptides. L-Methionine is an essential amino acid, meaning that it must be obtained it from the diet, since the body cannot synthesize it from other amino acids. The amino acid plays an important role in the body with methyl group metabolism, which is essential for normal liver and neurological function. Methionine can also act as free radical scavenger, making it useful to support the body’s antioxidant defenses.