As I mention in my book, N acetyl cysteine (NAC) is not found in food sources, but in the body, it converts into cysteine. NAC acts as a precursor to glutathione, a powerful NAC vs Glutathione: Differences, Similarities And Health Benefits Total Glutathione (T GSH) Assay Kit Products Servicebio Boost Your Health with NAC 500 mg N Acetyl Cysteine Sigma Aldrich Thioredoxin Reductase Assay Kit, 1 kit sufficient for 100 assays (1 mL) Yellow