Highly absorbable Pure + NAC amino acid preparation! Thanks to the herbal capsule, the product is also suitable for vegetarians and vegans. N-acetylcysteine, or NAC, is a form of an amino acid called cysteine ​​that is important to the body. N-acetylcysteine ​​is required for the production of glutathione in the liver. Cysteine ​​is a non-essential amino acid found naturally in the keratin of the skin, hair and nails.