GlyNAC pilot: 24 weeks raised glutathione in older adults, and gains faded after stopping
This 2021 open-label pilot trial gave eight older adults GlyNAC, a combination of glycine and N-acetylcysteine (NAC), for 24 weeks. It corrected their red-cell glutathione deficiency and oxidative stress and improved a range of measures including strength and walking speed. The benefits declined within 12 weeks of stopping.
What they did
This was a 36-week open-label trial, meaning everyone knew what they were taking and there was no placebo. Eight older adults and eight young adults were studied at the start. The young adults then left the study.
The older adults took GlyNAC for 24 weeks and were studied again, then stopped for 12 weeks and were studied a third time. Measurements included red-cell glutathione, how well mitochondria burned fuel, blood markers of oxidative stress and inflammation, blood vessel function, blood sugar and insulin, walking speed, grip strength, a six-minute walk, thinking tests, DNA damage and body composition.
What they found
After 24 weeks, GlyNAC corrected the older adults' red-cell glutathione deficiency, oxidative stress and mitochondrial fuel-burning problems. It also improved inflammation, blood vessel function, insulin resistance, DNA damage, thinking test scores, strength, walking speed and exercise capacity, and lowered body fat and waist size. GlyNAC was well tolerated.
The benefits declined after 12 weeks off GlyNAC.
What it can't tell us
With only eight older adults and no placebo group, this pilot cannot rule out chance or the effect of simply being in a study. The abstract does not give the dose, the participants' ages or the size of any change. Glutathione was measured in red blood cells, not cartilage, and the trial did not look at joints.
Why it matters
This pilot extended the earlier two-week result (Sekhar 2011) to six months and to whole-body measures such as strength and walking speed. The fall-off after stopping suggests the effect depends on continued supply. It set up the larger placebo-controlled trial (Kumar 2023) that followed.
The paper
- Kumar P, Liu C, Hsu JW et al. Glycine and N-acetylcysteine (GlyNAC) supplementation in older adults improves glutathione deficiency, oxidative stress, mitochondrial dysfunction, inflammation, insulin resistance, endothelial dysfunction, genotoxicity, muscle strength, and cognition: Results of a pilot clinical trial. Clin Transl Med 2021.
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