A nutritional supplement containing the biologically active L-isomer of the essential amino acid lysine, with potential anti-mucositis activity. Upon oral intake, L-lysine promotes healthy tissue function, growth and healing and improves the immune system. L-Lysine promotes calcium uptake, is essential for carnitine production and collagen formation. As collagen is essential for connective tissue maintenance, this agent may also help heal mucosal wounds. This may help decrease and prevent mucositis induced by radiation or chemotherapy.