Older adults made glutathione more slowly; two weeks of cysteine and glycine restored it
This 2011 human study found that eight older adults had lower glutathione in their red blood cells and made it more slowly than eight younger adults. After two weeks of supplementing with cysteine and glycine, the two building blocks the study tested, the older group's red-cell glutathione was about 95% higher and markers of oxidative stress fell.
What they did
Eight older and eight younger adults received an infusion of glycine labelled with a stable, non-radioactive tracer. This let the researchers measure how fast red blood cells were making new glutathione. They also measured glutathione and its building blocks in red cells, and markers of oxidative stress and oxidant damage in plasma, the liquid part of blood, including F2-isoprostanes.
The older adults were then given cysteine and glycine as a dietary supplement for two weeks and studied again.
What they found
Compared with the younger adults, the older adults had markedly lower red-cell glycine (218.0 versus 486.7 µmol/L), cysteine (19.8 versus 26.2 µmol/L) and glutathione (1.12 versus 2.08 mmol/L of red cells). They made glutathione more slowly, at about a third of the younger group's absolute rate, and had higher plasma oxidative stress and F2-isoprostanes.
After two weeks of supplements, the older adults' glutathione was 94.6% higher, its fractional synthesis rate 78.8% higher and its absolute synthesis rate 230.9% higher, and both oxidative stress markers were significantly lower. On these measures the supplemented older adults no longer differed from the younger adults.
What it can't tell us
This was a small study, eight people per group, and the supplement phase had no placebo group: the older adults were compared with themselves before and after. The abstract does not give the amounts or form of cysteine and glycine used, or the ages of the participants.
Everything was measured in blood. The study does not show what happens to glutathione in cartilage, and two weeks is too short to show any lasting health effect.
Why it matters
This study is the basis for the idea that glutathione falls with age because the body makes it more slowly, not only because it is used up faster. It also showed in people that supplying the building blocks, cysteine and glycine, brought production back up in older adults. It led directly to the later GlyNAC trials in this library.
The paper
- 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.
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