NAC for Thyroid Health Dr. Izabella Wentz, Pharm D NAC is one of those supplements that I always have on hand. It's impressive how broadly supportive NAC is. One time I was taking NAC 500 mg every day for about two Have you heard of NAC?? NAC (n acetyl cysteine) is a supplementation form of cysteine, a conditionally essential amino acid that helps replenish glutathione. It offers benefits for both fertility and pregnancy (like NAC Supplement (N Acetyl Cysteine) Amino Acid Capsules Metagenics UK