Two important updates on the future of NAC, a critical antioxidant supplement—and why we need to keep fighting for access. Action Alert! Last week, the FDA denied two Citizens Petitions from the supplement industry requesting the agency reach a determination that N-acetyl-L-cysteine (NAC) is included in the definition of a dietary supplement. Recall from our previous coverage that the agency has stated in warning letters to supplement makers that NAC does not meet the definition of a supplement because it was approved as a drug first in 1963. Read more.