he NAC-Glutathione Connection: Glutathione is vital to the body's antioxidant defense system. Adequate levels of glutathione may protect against atherosclerosis, cataracts, macular degeneration and some liver diseases. Although some supplements contain glutathione, it is preferable to take a precursor, such as NAC, to raise glutathione levels, because most supplemental glutathione is hydrolyzed in the gastrointestinal tract before being absorbed. NAC increases tissue levels of glutathione and is less expensive.