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 maintain normal, balanced immune system function. In addition, NAC can help to support healthy brain and neuronal tissues. Natural color variation may occur in this product.