Lysine is an amino acid that is essential for protein synthesis. Because it isn’t synthesized in the body, it must be obtained in the diet. Since the primary dietary sources for lysine are meat, poultry, and milk, many individuals, especially vegetarians, can be deficient. And the proteins in refined grains and cereals are typically low in lysine. Lysine has many biological functions, including the synthesis of connective tissues such as bone, skin, collagen, and elastin; the synthesis of carnitine and the resultant conversion of fatty acids to energy; support for healthy growth and development in children; and maintenance of healthy immune function.*