Glycine and N-acetylcysteine supplement in older adults over 16 weeks
What it found
Taking a combination of glycine and N-acetylcysteine for 16 weeks improved markers of cell stress, muscle strength, and blood pressure in older people.
The placebo group saw no such changes.
What they found
Studies in people
Cell protection and stress
Before the trial, older adults had much less glutathione than younger ones. After 16 weeks on glycine and N-acetylcysteine, their glutathione levels rose by 164% in muscle. Markers of cell damage dropped by 72%.
Muscle strength and walking
Older adults taking the supplement walked faster after 16 weeks, matching the speed of younger adults at the start. Their arm and leg strength also increased. The dummy pill group did not improve.
Blood pressure and waist size
After 16 weeks, the top blood pressure number fell in the supplement group. Their waist size also shrank. No changes happened in the dummy pill group or the younger adults.
Inflammation markers
Markers of inflammation in the blood were very high in older adults before the trial. Taking glycine and N-acetylcysteine for 16 weeks lowered several of these markers by up to 78%. A protective marker rose by 94%.
How the body uses fuel
Older adults had trouble burning fat for energy in their cells. After 16 weeks on the supplement, their ability to burn fat rose by 78%. This matched the levels seen in younger adults before the trial.
What the authors conclude
- They conclude that combining glycine and N-acetylcysteine is an effective way to improve many age-related problems in older adults.
- Their results show that benefits begin within 2 weeks but grow larger over 16 weeks.
- They suggest this combination works better than taking either ingredient alone because it supports the body's own cell protection system.
How it was done
Older adults often have lower levels of a key cell protector called glutathione, along with more inflammation and weaker muscles. Earlier work in mice showed that giving glycine together with N-acetylcysteine helped fix these problems, so the authors wanted to test this in people.
The researchers studied 24 older adults aged 61 to 80 and 12 younger adults aged 21 to 40. The older adults were split into two groups: one took capsules of glycine and N-acetylcysteine daily, and the other took a dummy capsule of alanine for 16 weeks. The younger adults took the active capsules for 2 weeks.
What it can’t tell you
- This trial only included 24 older adults who were generally healthy, so the results might differ in a larger or sicker group.
- The study lasted 16 weeks, so it cannot show whether these improvements last for years or affect how long people live.
- Because the supplement combined glycine with another ingredient, this trial alone cannot separate out what glycine does by itself.
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 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error