Lysine is one an essential amino acid that the body can not produce on its own. Though most lysine is obtained through proper diet, in some cases the use of the nutritional supplement (L-lysine HCl, as treatment or preventative measure can be beneficial.
Lysine is needed for proper protein and muscle growth, for repair of the body and is good for those recovering from injury or trauma. Lysine is also essential for proper calcium usage and growth in children, and plays a role in the production of carnitine, which is an amino acid that helps to convert fatty acids into energy and lower cholesterol. A deficiency of lysine can cause tiredness, nausea, loss of appetite, bloodshot eyes, dizziness and reproductive disorders.