Glutathione precursor
A glutathione precursor is a nutrient that cells use to make glutathione themselves, such as cysteine (often given as NAC), glycine, or glutamine as a source of glutamate. Precursors support the cell's own production rather than supplying finished glutathione.
Also called glutathione building block.
The case for precursors starts with what happens to glutathione itself when swallowed. Enzymes in the gut and liver break it down, and a single 3 g dose did not raise blood glutathione in seven healthy volunteers (Witschi 1992). Longer daily dosing has told a different story: six months of oral glutathione raised blood levels in a trial in 54 adults (Richie 2015), and liposomal glutathione raised them in a one-month pilot (Sinha 2018).
Precursors work on the cell's own production line, which is controlled mainly by cysteine supply and the activity of glutamate cysteine ligase (Lu 2013). In older adults who made glutathione slowly, two weeks of cysteine and glycine brought synthesis back to the level of younger adults (Sekhar 2011).
In cartilage cells in the lab, the protective effect of NAC disappeared when glutathione synthesis was blocked, showing that a precursor's effect runs through the cell's own glutathione production (Nakagawa 2010).
Sources
- Witschi A, Reddy S, Stofer B et al. The systemic availability of oral glutathione. Eur J Clin Pharmacol 1992.
- 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.
- Sinha R, Sinha I, Calcagnotto A et al. Oral supplementation with liposomal glutathione elevates body stores of glutathione and markers of immune function. Eur J Clin Nutr 2018.
- Lu SC. Glutathione synthesis. Biochim Biophys Acta 2013.
- Sekhar RV, Patel SG, Guthikonda AP et al. Deficient synthesis of glutathione underlies oxidative stress in aging and can be corrected by dietary cysteine and glycine supplementation. Am J Clin Nutr 2011.
- Nakagawa S, Arai Y, Mazda O et al. N-acetylcysteine prevents nitric oxide-induced chondrocyte apoptosis and cartilage degeneration in an experimental model of osteoarthritis. J Orthop Res 2010.
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