Pure Encapsulations NAC + Glycine - Cysteine and glycine are both necessary precursors for glutathione (GSH) synthesis, and co-supplementation of these nutrients promotes intracellular glutathione levels. Glutathione is one of the main endogenous antioxidants, acting in the body to recycle other antioxidants and protect the body from free radicals, as well as support detoxification. It is found in virtually every cell of the body and plays a critical role in cell function. Increased glutathione levels have been linked to supporting a reduction in oxidative stress.