A nonessential amino acid, cysteine is sulfur-containing, which means it helps positively maintain the structure of proteins in the body. Since it’s also a component of the powerful free-radical fighter glutathione, cysteine serves as a powerful antioxidant. Cysteine, though, is rarely used as a supplement. N-acetylcysteine* (or NAC for short) is more commonly used as a supplement because it is a more stable and readily absorbable form. As well, NAC, and not cysteine, has been used in almost all research that demonstrate its positive effects.
No deficiency conditions are known to exist.
No synergists have been noted.
No known toxicity.