Cells constantly make reactive molecules and constantly neutralise them. Glutathione is the most abundant molecule doing the neutralising.
Glutathione · Endogenous redox tripeptide
Normal metabolism produces reactive molecules that can damage proteins, fats and DNA. Cells keep them in check with a system of small molecules and enzymes, and glutathione is the most plentiful of those small molecules. Researchers measure it as a marker of oxidative stress and ask whether supplying it from outside changes anything. Evidence spans a century of biochemistry and a small number of human trials of oral glutathione.
Glutathione is a tripeptide of three amino acids: glutamate, cysteine and glycine. Unlike most peptides it is not made on ribosomes but assembled by two dedicated enzymes, and it is present in essentially all cells, typically at concentrations far higher than signalling peptides (Meister and Anderson 1983).
Its chemistry centres on the sulfur-containing thiol group of cysteine. Redox, in plain terms, is the transfer of electrons between molecules: a molecule that gives up electrons is oxidised, one that gains them is reduced. Glutathione gives up electrons to neutralise reactive molecules and in doing so pairs up as oxidised glutathione (GSSG); an enzyme then uses NADPH to convert it back to the reduced form (GSH). Because that cycle runs continuously, the ratio of GSH to GSSG is widely used in cell biology as a readout of oxidative stress: reactive molecules outpacing the systems that keep them under control (Forman et al. 2009).
The foundational literature is biochemical: how glutathione is synthesised, transported and recycled, and how its concentration changes with disease, drugs and age (Meister and Anderson 1983; Forman et al. 2009). That work describes the molecule cells make for themselves. Whether glutathione supplied from outside reaches cells intact is a separate question, and the two should not be confused.
Human studies of supplied glutathione have mostly used the oral route. In seven healthy volunteers, a single large oral dose did not raise plasma glutathione, cysteine or glutamate, and the authors concluded that systemic availability was negligible because the molecule is broken down by intestinal and liver enzymes (Witschi et al. 1992). A later six-month randomised placebo-controlled trial in 54 non-smoking adults reported increases in glutathione in blood cells and plasma with daily oral glutathione, returning to baseline after washout (Richie et al. 2015). The two results differ in design, duration and what was measured, and neither examined clinical outcomes.
Other research raises glutathione indirectly by supplying its precursors, cysteine and glycine, rather than glutathione itself; that is a different intervention and its findings do not transfer to a supplied glutathione formulation.
The central unresolved point is delivery: how much of a supplied formulation reaches tissues as intact glutathione, and whether a change in blood glutathione translates into any change in cell function. The human trials are small, use the oral route, and measure concentrations rather than health outcomes.
Endogenous glutathione is essential; that does not establish that adding more is useful, harmless or necessary in a person with normal levels. Route, formulation and stability matter: glutathione oxidises readily in solution, so the form and handling of any supplied material affect what is actually present.
The glutathione supplied here is a research material and is not an approved medicine in Australia.
Sources and status checked 2026-09-22
Glutathione — sizes and pricing