N-Acetyl Cysteine (NAC) is recommended to those who smoke, are sensitive to chemicals, and generally have a predisposition to coughing and/or weak lungs. They can significantly benefit by supplementing with NAC. It works with Vitamin C to enhance the immune system, and is important in the formation of glutathione, the body’s most important cellular antioxidant. NAC also thins mucus, improving many types of cough, COPD and bronchitis.