Does taking glutathione make sense, or does it get broken down in your gut?

Glutathione is indeed partially broken down in the gastrointestinal tract, but it does not disappear entirely. A well-designed study in 54 healthy adults showed that taking 250 to 1000 mg of glutathione daily for 6 months measurably raised glutathione levels in blood, red blood cells, and immune cells. At the highest dose (1000 mg per day), the increases were 30-35% in blood and immune cells, and as much as 260% in cheek lining cells. There is therefore genuine absorption, even if it is limited.

There is an important caveat to those results: once you stop taking the supplement, levels return to their original baseline within a month. The supplement therefore only raises levels for as long as you keep taking it. Whether higher glutathione levels in the blood also mean that your body genuinely benefits from them is a separate question that the studies do not answer.

For the skin, the evidence is thinner. A summary of four small studies found a modest brightening effect of 500 mg per day on sun-exposed skin. Effects on wrinkles and elasticity were not demonstrated in a statistically convincing way. The researchers themselves concluded that the evidence is too limited for firm conclusions.

Building up glutathione in the brain is a different matter altogether. Even a very high dose of a glutathione building block (N-acetylcysteine, 6000 mg per day for 28 days) did not measurably raise glutathione levels in the brains of a small group of Parkinson's patients. This suggests that with oral supplements you cannot reach hard-to-access organs such as the brain by this route. In three of the five patients, side effects also occurred at that high dose.