Question:
What is N-acetyl L-cysteine?
Answer:

N-acetyl L-cysteine is a derivative of the amino acid cysteine, one of the building blocks of glutathione. Glutathione deficiencies can be reversed through an increased intake of cysteine, and the most effective supplemental form is the cell-permeable form of N-acetyl-L-cysteine.

Glutathione and N-acetyl-L-cysteine continue to be the subjects of active research in many areas of health and disease. Glutathione's importance as a free radical scavenger derives from two characteristics. First, it is extremely abundant, perhaps the most abundant low-molecular-weight peptide in the body. Second, it plays a central role in the glutathione redox cycle, a complex biochemical system responsible for neutralizing free radicals and providing protection from free hydroperoxides and lipid peroxides.