Glycine and NAC supplement in older adults
What it found
In 24 older adults, a supplement of glycine plus N-acetylcysteine improved markers of aging over 16 weeks.
The authors say it was well tolerated.
What they found
Studies in people
Glutathione levels
Older adults had 66% lower muscle glutathione than young adults at baseline. GlyNAC raised muscle glutathione by 121% after 2 weeks and 164% after 16 weeks, reaching levels similar to young adults. No improvement occurred with placebo.
Oxidative stress markers
Older adults had much higher levels of oxidative stress markers (TBARS 424% higher, F2-isoprostanes 301% higher) than young adults. GlyNAC lowered TBARS by 72% and F2-isoprostanes by 72% after 16 weeks, to levels similar to young adults. Placebo had no effect.
Mitochondrial function
Older adults had impaired mitochondrial fatty-acid oxidation and higher glucose oxidation. GlyNAC improved these measures after 2 and 16 weeks, while placebo did not.
Physical function
Older adults had slower gait speed and shorter 6-minute walk distance than young adults. GlyNAC increased gait speed and muscle strength after 16 weeks, but placebo did not.
Inflammation and insulin resistance
Older adults had higher levels of inflammatory markers and insulin resistance. GlyNAC lowered these markers and improved insulin sensitivity after 16 weeks, while placebo did not.
Aging hallmarks
GlyNAC improved seven aging hallmarks, including mitochondrial dysfunction, inflammation, insulin resistance, and cellular senescence. Placebo had no effect.
What the authors conclude
“GlyNAC supplementation in OA for 16-weeks was safe and well-tolerated.”
Also in their conclusions
- They conclude that GlyNAC supplementation in older adults improves glutathione deficiency, oxidative stress, mitochondrial dysfunction, inflammation, insulin resistance, endothelial dysfunction, physical function, and multiple aging hallmarks.
- They state that GlyNAC supplementation was safe and well-tolerated.
- They suggest that GlyNAC is an effective nutritional supplement that improves and reverses multiple age-associated abnormalities to promote health in aging humans.
How it was done
The authors wanted to test whether supplementing older adults with glycine and N-acetylcysteine could improve glutathione deficiency, oxidative stress, mitochondrial dysfunction, insulin resistance, physical function, and aging hallmarks.
They studied 24 older adults (aged 61-80) and 12 young adults (aged 21-40). Older adults were randomly assigned to receive either GlyNAC (glycine plus N-acetylcysteine) or a placebo (alanine) for 16 weeks; young adults received GlyNAC for 2 weeks. Participants were assessed before, after 2 weeks, and after 16 weeks.
What it can’t tell you
- This trial included a small number of older adults who were relatively healthy, so the results may not apply to all older people or those with multiple health conditions.
- The study lasted only 16 weeks, so it cannot show whether the benefits last longer or whether they lead to improved long-term health outcomes.
- The trial cannot prove that GlyNAC prevents disease or extends life in humans.
Who paid
- Funding
- Funded by NIA NIH HHS (from the PubMed record).
- Authors work at
- Baylor College of Medicine, USA
The paper
- Title
- Supplementing Glycine and N-Acetylcysteine (GlyNAC) in Older Adults Improves Glutathione Deficiency, Oxidative Stress, Mitochondrial Dysfunction, Inflammation, Physical Function, and Aging Hallmarks: A Randomized Clinical Trial
- Type
- Randomised controlled trial
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Kumar P, Liu C, Suliburk J, et al (2023). Supplementing Glycine and N-Acetylcysteine (GlyNAC) in Older Adults Improves Glutathione Deficiency, Oxidative Stress, Mitochondrial Dysfunction, Inflammation, Physical Function, and Aging Hallmarks: A Randomized Clinical Trial. The journals of gerontology. Series A, Biological sciences and medical sciences. doi:10.1093/gerona/glac135Free full textPubMed 35975308DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error