A sulfur-containing amino acid. Its
sulfhydril group is very effective at binding
free radicals and prevent their toxic effects. It is not one of the
essential amino acids, but blood levels can easily be raised above baseline by supplementation. Cysteine's
antioxidant function is similar to that of
glutathinone, but cysteine is less expensive and more
bioavailable.
Cysteins is particularly effective at preventing the
cross-linking damage done by
ethanol's toxic metabolite,
acetaldehyde. Many sources recommend taking up to several grams of cysteine while drinking to prevent
hangover (my personal experience supports the idea).
The biologically active
isomer of cysteine is L-cysteine. It is often sold in the form of N-
acetyl-cysteine, or NAC, which is a more stable molecule.
Information is from an article by Dr. Steven Fowkes at http://www.ceri.com/alcohol.htm, though I've confirmed much of it elsewhere.