GGT (Gamma-Glutamyl Transferase)
A liver and biliary enzyme that already sits inside most standard liver panels, sensitive to alcohol intake and hepatic oxidative stress. It rises with alcohol use, cholestasis and oxidative stress, and some cohort studies associate elevated GGT — even within the “normal” range — with cardiometabolic risk and all-cause mortality, plausibly as a marker of oxidative stress or of alcohol intake that was never disclosed.
Well validated as a component of a cholestatic liver injury workup and as an alcohol-use marker. The independent “longevity marker” association, beyond that established role in standard liver assessment, is observational, non-specific, and has not been incorporated into any major risk calculator or guideline as a standalone target.