In a placebo-controlled trial, 16 weeks of GlyNAC corrected low glutathione in older adults
This 2023 randomised, placebo-controlled trial gave 24 older adults either GlyNAC, a combination of glycine and N-acetylcysteine, or a placebo for 16 weeks. GlyNAC, and not placebo, corrected glutathione deficiency and improved oxidative stress, inflammation, walking speed and muscle strength.
What they did
Twenty-four older adults were randomly assigned to GlyNAC (12 people) or a placebo of alanine, an amino acid matched for nitrogen content (12 people), for 16 weeks. Twelve young adults took GlyNAC for two weeks for comparison.
Everyone was studied before, after two weeks and after 16 weeks. The researchers measured glutathione, oxidative stress, mitochondrial fat-burning, inflammation, blood vessel function, insulin resistance, a set of biological markers of ageing, walking speed, muscle strength, a six-minute walk, body composition and blood pressure.
What they found
At the start, compared with the young adults, the older adults had glutathione deficiency, more oxidative stress, poorer mitochondrial function, more inflammation, poorer blood vessel function, insulin resistance, several markers of ageing, poorer physical function, larger waists and higher systolic blood pressure.
GlyNAC, but not placebo, improved or corrected these problems in the older adults. GlyNAC was safe and well tolerated over the 16 weeks.
What it can't tell us
The trial was small, 12 people per group, and the abstract does not give the dose, the participants' ages, whether it was blinded, or the size of each change. Glutathione was measured in blood, not cartilage, and the trial did not assess joints. Sixteen weeks says nothing about longer-term effects.
Why it matters
This is the strongest trial in this library for GlyNAC, because it had a placebo group and random allocation. It supports the earlier pilot findings (Kumar 2021) and the idea that supplying the building blocks of glutathione can raise glutathione in older adults who start low. A larger trial with a different design (Lizzo 2022) found a less clear-cut result, which is worth reading alongside it.
The paper
- Kumar P, Liu C, Suliburk J et al. 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. J Gerontol A Biol Sci Med Sci 2023.
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