https://aminoacids.substack.com/p/antio ... amino-acid
TLDR:
GlyNAC is 2 amino acids that may help the body to produce more glutathione, an antioxidant that helps a lot, including to help generate other antioxidants in the body, especially in older adults and vegans/vegetarians. Instead of taking "exogenous" antioxidants, taking precursors that help the body do its thing may be "antioxidant 3.0".