Body cells and tissues are threatened continuously by damage caused by toxic free radicals and reactive oxygen species (e.g., peroxides) which are produced during normal oxygen metabolism, by other chemical reactions, and by toxic agents in the environment. Free radicals are capable of disrupting metabolic activity and cell structure. When this occurs, additional free radicals are produced which, in turn, can result in more extensive damage to cells and tissues. The uncontrolled production of free radicals is thought to be a major contributing factor to many degenerative processes seen during aging. Glutathione is a naturally-occurring tripeptide of L-cysteine, L-glutamate and L-glycine. Glutathione is the essential co-substrate for two major antioxidant enzymes in the body; glutathione peroxidase and glutathione reductase. As such, glutathione offers one mechanism for scavenging toxic free radicals. Glutathione enters the blood and other extracellular compartments where it exerts much of its beneficial antioxidant effects.
N-Acetyl L-cysteine (NAC) is a precursor for the sulfur amino acid cysteine, and cysteine is used by the body to synthesize glutathione. In contrast to glutathione, NAC is efficiently transported into the cell where it is readily converted to L-cysteine for glutathione synthesis. NAC is well absorbed, and unlike L cysteine, is virtually non-toxic. NAC is recognized as a safe, highly effective means of increasing intracellular glutathione stores. Aside from providing cysteine as a glutathione precursor, NAC also appears to have antioxidant properties by itself, and is a valuable sulfur donor for various metabolic needs.