L-Lysine is an essential amino acid that the body uses to build proteins. As an amino acid, L-Lysine helps your body to produce proteins, enzymes, collagen and antibodies. L-Lysine supports healthy immune system, healthy connective tissues, healthy organs and respiratory health. L-Lysine may support weight loss as it helps to convert fatty acids into energy and promotes lean muscle mass. It may also support bone health by promoting the intestinal absorption of calcium.