NAC or Glutathione? Which Supplement Is Better? in 2026 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 Effects of N acetylcysteine, oral glutathione (GSH) and a novel sublingual form of GSH on oxidative stress markers: A comparative crossover study. ScienceDirect Glutathione is the body's master antioxidant. It is important for handling oxidative stress, detoxification, and immune health. Low glutathione is linked to many chronic illnesses. Knowing what your body needs to make