nac is a precursor to glutathione biosynthetic scheme. N-acetyl-L-cysteine (NAC) can supply Glutathione vs. NAC: An Expert

This mechanism successfully restrains the proliferation and inflammatory reactions of RA-FLS, markedly reduces joint injury in RA model rats, and clearly exhibits the anti-inflammatory properties of HDAC4 ( However, certain isoforms exhibit pro-inflammatory effects

Your liver produces it to neutralise free radicals, support immune function, and maintain cellular health

Effect of supplementation with a cysteine donor on muscular performance

Topical collagen products often contain large collagen molecules that are not easily absorbed by the skin, meaning they mostly stay on the surface rather than penetrating into deeper layers

Busse PJ, Schofield B, Birmingham N, Yang N, Wen M, Zhang T, et al