N-acetylcysteine (NAC) is a popular dietary supplement known for its antioxidant properties. It’s a derivative of the amino acid L-cysteine and plays a critical role in the production of glutathione, one of the body’s primary antioxidants. Glutathione helps neutralize harmful free radicals and reduce oxidative stress, which is linked to aging and various diseases. As a supplement, NAC has been used to support respiratory health due to its mucolytic action, which helps break down mucus in the airways.