NAC helps break down mucus. Double-blind research has found that NAC supplements improved symptoms and prevented recurrences in people with chronic bronchitis. NAC may also protect lung tissue through its antioxidant activity. NAC helps the body synthesize glutathione, an important antioxidant. In animals, the antioxidant activity of NAC protects the liver from the adverse effects of exposure to several toxic chemicals. NAC also protects the body from acetaminophen toxicity and is used at very high levels in hospitals for patients with acetaminophen poisoning. It has also been shown to be effective at treating liver failure from causes other than acetaminophen poisoning (e.g., hepatitis, and other drug toxicity)5 and at preventing kidney damage caused by injections of iopromide, a contrast medium used in people scheduled to undergo computerized tomography (CT) imaging. Supplementation with NAC has been shown to reduce the proliferation of certain cells lining the colon and may reduce the risk of colon cancer in people with recurrent polyps in the colon. There have been several case reports of oral NAC producing dramatic improvements in Unverricht-Lundborg disease, an inherited degenerative disorder involving seizures and progressive disability. One study used 3 grams of NAC per day. Oral supplementation with NAC has been used successfully in two cases to treat a rare syndrome that complicates kidney dialysis This condition, known as pseudoporphyria, has no other known treatment. Controlled clinical trials are needed to confirm these preliminary observations. People undergoing a certain cardiac procedure (coronary angiography) are at risk of developing kidney damage from the injected dye that is used to visualize the coronary arteries. In a double-blind study, oral administration of NAC reduced by 86% the incidence of kidney damage in people undergoing this procedure. The amount of NAC used in that study was 400 mg twice a day, on the day before and the day of the procedure. Other studies have shown that NAC is protective only when a low dose of dye is used.