Cysteine is an amino acid, a building block of proteins that are
used throughout the body. When taken as a supplement, it is
usually in the form of N-acetyl-L-cysteine (NAC). The body makes
this into cysteine and then into glutathione, a powerful
antioxidant. Antioxidants fight free radicals, harmful compounds
in the body that damage cell membranes and DNA. Researchers
think free radicals play a role in aging as well as the
development of a number of health problems, including heart
disease and cancer. NAC can help prevent side effects caused by
drug reactions and toxic chemicals, and helps break down mucus
in the body. It seems to have benefits in treating some
respiratory conditions, such as bronchitis and COPD. N-acetyl
cysteine (NAC) may be used in preventing or treating the
following conditions: Doctors often give intravenous (IV) NAC to
people who have taken an overdose of acetaminophen (Tylenol), to
help prevent or reduce liver and kidney damage. Acetaminophen
poisoning can also happen at lower doses i