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 is also necessary for the formation of glutathione.* Molybdenum and selenium are essential trace minerals that facilitate the production of several important enzymes.* Take 1 capsule twice daily. Black speckling may occur over time after package is opened but product is safe to consume. NAC is a sulfur-containing amino acid so an unpleasant smell is possible. Leave dessicant and charcoal packets in bottle after opening to delay oxidation and control odor (if any).