NAC supplement n-acetyl cysteine is a unique amino acids supplement - a source of the conditionally essential amino acid L-cysteine and a precursor to the tripeptide glutathione. NAC and glutathione support antioxidant and detoxification activity in the body. N acetyl cysteine NAC supplements have been used as liver detox supplements, liver detox cleanse support, a cardiovascular support supplement, and as an antioxidant supplement.