N-acetyl-L-cysteine (NAC) is the acetylated form of L-cysteine that has been used to break up pulmonary and bronchial mucous.1-3 It is very efficiently absorbed and has been shown to protect cells directly and support the immune system.4-15 NAC is an antioxidant and a free radical-scavenging agent that increases intracellular glutathione at the cellular level. NAC can act as a precursor for glutathione synthesis as well as a stimulator of the cytosolic enzymes involved in glutathione regeneration.16,17 NAC has been shown to protect against oxidative stress-induced neuronal death in cultured granule neurons.18

NAC is an antioxidant that increases intracellular glutathione at the cellular level. NAC can act as a precursor for glutathione synthesis as well as a stimulator of the cytosolic enzymes involved in glutathione regeneration. NAC is the more efficiently absorbed and used form of the amino acid L-cysteine. L-cysteine plays a role in the sulfation cycle, acting as a sulfur donor19 in phase II detoxification and as a methyl donor in the conversion of homocysteine to methionine.20,21 N-acetyl-L-cysteine also enhances immune function.22-25 NAC attenuates the progression of the abnormal retention of lipids within liver cells by decreasing development of oxidative stress and subsequent increases in TNF-alpha.26 In addition, N-acetyl-L-cysteine is used to support bronchial health.27-30

Those who supplement with NAC should drink six to eight glasses of water daily to prevent cysteine renal stones. Cysteine renal stones are rare but do occur.