NAC is the supplement form of Cysteine, a semi-essential amino acid produced in low amounts by the body. Cysteine and NAC are essential to produce the antioxidant Glutathione, the most potent antioxidant in your body. Glutathione is essential for immune health and is known to combat free radicals in the body.[1] It has also been known to combat infertility and heart disease caused by oxidative damage[2]