What glutathione is, and what the trial that actually tested it found

Glutathione is a tripeptide — glutamate, cysteine and glycine — that the body synthesises itself and that is the most abundant endogenous antioxidant. Unlike NAD+, with which it is often sold, this one really is a peptide and fits a peptide catalogue without strain.

The trial that tested it, and it must be read in full

A randomised, double-blind, placebo-controlled trial followed 54 non-smoking adults for six months on oral glutathione supplementation, measuring levels in blood, erythrocytes, plasma, lymphocytes and buccal mucosal cells [1].

• It rose. At six months, mean levels increased by 30 to 35% in erythrocytes, plasma and lymphocytes in the high-dose group, and by 260% in buccal cells. In the low-dose group they rose 17% in blood and 29% in erythrocytes [1].
• With less oxidative stress. The ratio of oxidised to reduced glutathione in whole blood fell at six months in both groups [1].
• And here is the detail almost nobody cites: after a one-month washout without supplementation, levels returned to baseline [1].

That last point does not invalidate the result, it defines it. What the trial shows is that supplementation maintains higher levels while it lasts, not that it refills a store that then stays full.

And a point of form that matters: that trial was oral. A vial to be prepared and given another way does not automatically share its results.

The other trials commonly cited are not of glutathione

Two recent trials in older adults describe improvements in glutathione deficiency, oxidative stress, mitochondrial dysfunction, inflammation, physical function and ageing markers [2][3].

They are good studies and are often cited to sell glutathione. But what they supplement is glycine and N-acetylcysteine, two precursors, so the body makes its own. They do not administer the tripeptide. It is the same confusion as with NAD+, and it is worth flagging because whoever makes it almost always makes it in their own favour.

What there is not

There is no approved indication for glutathione as a medicine in the European Union or the United States.

This page describes published literature. It is not medical information, it does not describe a therapeutic use, and it does not replace any healthcare professional.

What to look at when comparing suppliers

• Reduced or oxidised form, stated explicitly. The antioxidant activity belongs to the reduced form, and both exist.
• Purity for the specific batch, with a certificate you can read before buying.
• Storage. It is a compound that oxidises readily; how it travelled and how it is kept matters as much as what the analysis said.