Product description N-acetyl cysteine derived from the amino acid L-cysteine. Amino acids are the building blocks of proteins. It is known as semi-essential because your body can produce it from other amino acids, namely methionine and serine. It becomes essential only when the dietary intake of methionine and serine is low. Aiwo NAC replenish the most powerful antioxidant in your body- glutathione, also help with chronic respiratory conditions, fertility and brain health.