Glutathione

Glutathione (GSH) is a small protein-like molecule (a tripeptide) that cells build from three amino acids — glutamate, cysteine, and glycine. It is the main antioxidant working inside cells, neutralising reactive oxygen species and helping recycle other antioxidants such as vitamins C and E.

It works as the cell's redox buffer: the sulfur-containing (–SH) group on its cysteine donates electrons to neutralise free radicals, turning into an oxidised form (GSSG) that enzymes then regenerate back to GSH using NADPH. Glutathione also tags toxins and drugs for elimination as part of the liver's phase-II detoxification.

A practical catch: swallowed glutathione is largely broken down in the gut, so oral absorption is limited, and cysteine availability often caps how much the body can make (which is why precursors like NAC are used). Evidence that systemic supplementation delivers the marketed benefits is mixed, intravenous use is off-label, and it is not an approved therapeutic for most of those claims.