Source Naturals, N-Acetyl Cysteine, 1,000 mg, 180 TabsProduct Description N acetyl cysteine is a more stable form of the sulfur amino acid L cysteine, and is a powerful cysteine and glutathione precursor. Glutathione is a major antioxidant as the cofactor for glutathione peroxidase, one of the most important antioxidant enzymes in the body. Additionally, a meta analysis of human trials has reported that N acetyl cysteine supplementation supports respiratory health.* Product Benefits Antioxidant Support*.