Antioxidant Support for Health and Longevity. N-Acetyl-L-Cysteine capsules contain a highly stable form of cysteine an important sulfur-containing amino acid. NAC is a precursor to glutathione a critical antioxidant scientifically proven to scavenge free radicals. NAC has the unique ability to maintain healthy lung tissue support the body's natural defenses and enhance cellular health and longevity. These qualities make NAC especially beneficial for active people the elderly and those exposed to polluted environments.