NAC is a powerful antioxidant that works to reduce inflammation and oxidative stress in the body. Oxidative stress occurs when you have an imbalance of antioxidants and free radicals, which causes toxic and damaging effects to your cells. In this article, we’ll review a supplement called N-acetyl-cysteine (NAC) for PCOS, how it may improve menstrual cycles, fertility, and other PCOS symptoms.