Promotes cellular health Offers immune and antioxidant support Free of gluten, dairy, soy, nuts, sugar, salt, preservatives, and artificial colors or flavors NAC, or N-Acetyl-L-Cysteine, is a source of the essential amino acid L-cysteine?a precursor to the antioxidant glutathione. NAC is believed to help support cellular health and the immune system. These once-daily capsules are both convenient and easy to incorporate into your daily wellness routine.