N-acetyl cysteine (NAC) is an amino acid that boosts antioxidant function and is commonly used as an agent to help clear sinus and airway congestion caused by mucus overproduction. NAC is a source of the conditionally essential amino acid L-cysteine and is a precursor to the tripeptide glutathione, an essential intracellular antioxidant, and, therefore, supports antioxidant and cellular detoxification pathways in the body. In addition, a growing body of research also highlights the role of NAC in supporting neuropsychiatric health. Each capsule of NAC provides 500 mg of this versatile amino acid.