N-Acetyl-L-Cysteine (NAC) Sustain is a powerful antioxidant amino acid and a precursor in the body to the critical antioxidant glutathione.* N-Acetyl-L-Cysteine supplies readily available L-cysteine, which acts as an antioxidant itself or as a precursor to glutathione. Glutathione is one of the body’s most important and abundant antioxidant and detoxification agents.* Glutathione is essential for the immune system’s proper functioning, is vital in maintaining healthy tissue, and supports liver function.* NAC Sustain is formulated with advanced bilayer Sustain tablets that combine 1/3 Quick Release and 2/3 Sustained Release formats.