With Selenium & Molybdenum Maintains Cellular Health Non-GMO A Dietary Supplement How It Works: N-Acetyl-Cysteine (NAC) is a stable form of the non-essential amino acid L-Cysteine. Cysteine is a sulfur-containing amino acid that acts as a stabilizer for the formation of protein structures. Although NAC possesses its own free radical scavenging activity, its primary function in the body is to supply Cysteine necessary for glutathione synthesis and replenishment. This unique formula also contains Molybdenum, an essential trace element that functions as a cofactor in many biochemical reactions, and Selenium, another trace mineral that supports glutathione production.