N-acetyl-cysteine (NAC) is a stable and bioactive form of cysteine, an amino acid that plays a key role in phase II detoxification and homocysteine metabolism.* NAC is efficiently transported into the cell, where it is readily converted to cysteine for glutathione synthesis and regeneration.* Because NAC can penetrate the blood-brain-barrier, it is especially important for maintaining healthy brain and nervous system tissues.* NAC also helps to support respiratory health by promoting normal mucus viscosity.*