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N-acetyl cysteine (NAC) is an altered form of the amino
acidcysteine, which is commonly found in food and synthesized by the
body.
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 when used in connection with liver
failure from causes other than acetaminophen poisoning (e.g.,
hepatitis, and other drug toxicity) 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
when used in connection with 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.
Dosage and
Administration
Healthy people do not need to
supplement NAC. Optimal levels of supplementation remain unknown,
though much of the research uses 250–1,500 mg per
day.
Possible Side Effects
One study
reported that 19% of people taking NAC orally experienced nausea,
vomiting, headache, dry mouth, dizziness, or abdominal pain. These
symptoms have not been consistently reported by other
researchers.
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