L-Lysine capsules with selenium and zinc The L-Lysine plus capsules also contain the trace elements selenium and zinc in addition to the amino acid lysine. L-Lysine is an essential amino acid found predominantly in animal-based foods and cannot be produced by the body itself. Like all proteinogenic (protein-building) amino acids, L-Lysine is a component of body proteins. Selenium and zinc contribute to the normal function of the immune system and to the protection of cells from oxidative stress. Additionally, zinc plays a role in cell division and contributes to normal acid-base metabolism and the maintenance of normal skin.