Six months of daily oral glutathione raised glutathione stores in healthy adults
This 2015 randomised, double-blind, placebo-controlled trial gave 54 non-smoking adults oral glutathione at 250 or 1,000 mg a day, or placebo, for six months. Glutathione rose in blood, red cells, plasma, white cells and cheek cells, by 30 to 35% in blood compartments on the higher dose, and fell back after a month off.
What they did
Researchers randomly assigned 54 non-smoking adults to oral glutathione at 250 mg or 1,000 mg a day, or to placebo, for six months. Neither the participants nor the researchers knew who was taking what.
They measured glutathione in whole blood, red blood cells, plasma, lymphocytes (a type of white blood cell) and cells gently scraped from the inside of the cheek, at 1, 3 and 6 months and after a one-month break. A subset also had immune markers measured.
What they found
Glutathione in blood rose at 1, 3 and 6 months compared with starting levels, on both doses. At six months on the higher dose, average glutathione was 30 to 35% higher in red cells, plasma and lymphocytes and 260% higher in cheek cells. On the lower dose, it was 17% higher in whole blood and 29% higher in red cells.
Most increases grew with dose and time, and levels returned to baseline after a one-month washout. In both dose groups the ratio of oxidised to reduced glutathione in whole blood fell after six months, a sign of lower oxidative stress. Natural killer cell activity, a measure of immune function, more than doubled on the higher dose compared with placebo at three months.
What it can't tell us
The participants were healthy adults and the abstract does not give their ages, so it cannot say whether older adults or people with joint problems respond the same way. Glutathione was measured in blood and cheek cells, not cartilage.
The abstract reports the glutathione rises against each group's starting levels; it does not set out the comparison with the placebo group for those measures. It also does not explain how glutathione got in, given the earlier view that it is broken down in the gut.
Why it matters
This trial challenged the long-held view, based on single-dose studies such as Witschi 1992, that oral glutathione is not absorbed. Its design differed: daily dosing for months rather than one dose, and glutathione measured in several blood compartments rather than plasma alone. The two studies do not cancel each other out; they answer different questions.
The paper
- Richie JP Jr, Nichenametla S, Neidig W et al. Randomized controlled trial of oral glutathione supplementation on body stores of glutathione. Eur J Nutr 2015.
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