NAC is a stable form of L-cysteine that acts as a precursor to glutathione, a potent intracellular antioxidant involved in DNA synthesis and repair, protein synthesis, and immune response. NAC is recognized for its ability to replenish intracellular levels of glutathione, helping to protect against oxidative stress. It also has mucolytic properties, breaking down mucus in the airways and thus commonly used as an adjunct treatment for respiratory conditions. NAC's immune- supporting role is particularly noted in conditions characterized by decreased glutathione levels.*