NAC 1000 mg (N-Acetyl Cysteine), 120 Tablets, NOW FoodsNOW NAC 1000 mg Free Radical Protection. Maintains Cellular Health. Normal Immune System Function. Vegetarian Vegan. Non GMO. A Dietary Supplement. N acetyl cysteine (NAC) is a stable form of the non essential amino acid cysteine. It is a sulfur containing amino acid that acts as a stabilizer for the formation of protein structures, and promotes the formation of glutathione. Glutathione is a powerful free radical scavenging compound that also helps to