Pure Encapsulations PureDefense w/NAC CapsulesPure Encapsulations PureDefense W NAC Supports healthy immune function during seasonal changes while helping maintain healthy energy levels.* This powerful supplement is made with NAC, or N acetyl cysteine. But, what is NAC? Cysteine is an important amino acid that helps promote the production of certain antioxidants in your body, particularly glutathione, which supports your bodys natural detoxification process.* Promotes healthy glutathione levels*