L Lysine is an essential amino acid; therefore it must be obtained from the diet as the body cannot produce it on its own. L Lysine has long been considered an excellent treatment for the prevention of cold sores &, in more recent years, has been attracting attention as an excellent addition to the already long list of mass building nutrients. L Lysine is an essential building block for all protein in the body & also plays a major role in: calcium absorption, building lean tissue, recovering from surgery or sports injuries. L Lysine supplementation has been shown to increase the absorption of calcium. Lysine also works with other essential amino acids to maintain growth, lean body mass, & improve the body's store of nitrogen.