N-acetyl cysteine (NAC) is a supplement derived from the amino acid L-cysteine. It serves as a precursor to glutathione, an important antioxidant in the body. NAC is commonly used to support respiratory health, liver function, and detoxification. In capsule form, NAC provides a convenient way to supplement one's diet with this beneficial compound. It's often utilized to promote overall wellness and support specific health goals, such as antioxidant protection and immune system function.