N-acetylcysteine (NAC)

N-acetylcysteine (NAC) is an acetylated derivative of L-cysteine, a sulphur-containing amino acid naturally present in the body. It is best known as a precursor to glutathione, one of the main endogenous antioxidants produced by human cells. Its superior bioavailability compared to free cysteine makes it a particularly well-studied form of supplementation. NAC contributes to protecting cells against oxidative stress by supporting glutathione synthesis. It is also recognised for its mucolytic properties — its ability to thin bronchial secretions — making it a well-documented compound in the respiratory field. It also contributes to normal liver function by taking part in the body's natural hepatic detoxification mechanisms. NAC supplementation may be of interest when dietary intake of sulphur amino acids is insufficient, or in contexts of elevated oxidative stress. It is generally well tolerated and is available in capsule or powder form.