Supply your body with a powerful antioxidant with Jarrow's N-acetyl-l-cysteine in 500 milligrams per serving. N-acetyl-l-cysteine (NAC) is an amino acid and antioxidant. It is a precursor in the body to the critical antioxidant glutathione, which is produced intracellularly by the liver. In fact, some health experts believe that supplementation with NAC is the preferred way to increase levels of glutathione rather than supplementing with glutathione itself. Glutathione exerts a variety of protective effects including detoxification and cellular defense against oxidative stress. Gluten free.