Glycine and N-Acetylcysteine (GlyNAC) in Aging Research
GlyNAC pairs glycine with N-acetylcysteine to raise glutathione. Small trials in older adults report biomarker gains, and a larger one did not meet its main goal. Evidence, funding and limits.
Content last updated . This page has not been medically reviewed.
Quick answer
GlyNAC is a combination of two substances: glycine (an amino acid) and N-acetylcysteine (NAC, a form of the amino acid cysteine). Both are building blocks of glutathione, a molecule cells use to handle oxidative stress. Small trials from one research group report that GlyNAC raised glutathione and improved many measures in older adults. A larger trial funded by a food company did not raise glutathione overall. No trial has shown that GlyNAC extends human life or prevents disease. Labels: promising but limited, mixed, preclinical (cells/animals only) for lifespan.
What the research claims
The idea: glutathione levels fall with age, and giving the two raw materials could restore them. A review by the main research group describes GlyNAC as improving glutathione deficiency, oxidative stress, mitochondrial function, inflammation, insulin resistance, strength and cognition, and calls its own findings in need of confirmation in a randomized trial. [1] A separate review notes that glutathione levels decline in aging, and that cysteine supply and its precursor NAC are limiting steps. [2]Human trials
| Trial | Design | Result |
|---|---|---|
| 2021 pilot | Open-label, 8 older adults and 8 younger adults, 24 weeks of GlyNAC then 12 weeks off | Many measures improved on GlyNAC; benefits declined after stopping. No placebo group. [3] |
| 2023 randomized trial | 24 older adults (12 on GlyNAC, 12 on placebo) for 16 weeks, plus 12 younger adults for 2 weeks | Reported improved glutathione, oxidative stress, inflammation and physical function with GlyNAC; described as safe and well tolerated. Small trial. [4] |
| 2022 randomized trial | 114 healthy volunteers, mean age 65, 2 weeks at three amounts | Glutathione did not rise overall (primary endpoint). A post hoc subgroup with high oxidative stress and low glutathione showed an increase. Safe and well tolerated. [5] |
Related guides
Ingredient profiles: glycine, N-acetylcysteine and glutathione. Wider context: mitochondria and oxidative stress in aging and antioxidant supplements and aging.Frequently asked questions
Does GlyNAC reverse aging?
No. The 2023 trial authors describe reversing age-associated abnormalities, but it had 12 older adults per arm and measured no outcome such as survival or disease. [4]
Did the largest trial work?
Not on its main goal. Glutathione did not rise overall in the 114-person trial; a post hoc subgroup did show a rise. [5]
Does GlyNAC extend lifespan?
In mice, one study reported 24% longer life. No human lifespan data exist. [6]
Is NAC allowed as a supplement in the US?
FDA says NAC is excluded from the supplement definition but has a 2022 enforcement discretion policy for certain products. [7]
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
How to read these results
- Results disagree. The 114-person trial missed its primary endpoint, and its subgroup finding was exploratory (post hoc). [5]
- Biomarkers dominate. Glutathione levels and oxidative-stress markers are laboratory values. Gait speed, muscle strength and a 6-minute walk test were also measured in the 2023 trial, but the sample sizes [4] of 8 to 12 per group leave wide uncertainty.
- Duration. The longest trial period was 24 weeks. No trial measured falls, disability, disease, or survival.
- Funding and conflicts. The 2022 trial's authors included employees of Nestlé research units; its record states that Nestlé Health Science holds patents and markets products for glycine and NAC. [5] The 2023 trial's record lists US National Institute on Aging grants; we did not read a conflict-of-interest statement for it. [4]
- Lifespan (mice only). A 2022 mouse study reported GlyNAC-fed C57BL/6J mice lived 24% longer than controls. It is a single mouse strain, and it cannot be assumed to apply to people. [6]
Regulation and quality of NAC
In the US, FDA's position is that NAC is excluded from the definition of a dietary supplement. A 2022 guidance says FDA intends to use enforcement discretion for certain NAC products labeled as dietary supplements that would otherwise be lawful. [7] That is not an approval of NAC for any use in aging. Rules in other countries were not verified. Laws change; this is not legal advice.
Safety
The trials above reported GlyNAC as safe and well tolerated in healthy older adults over weeks to months. [4][5] They do not establish long-term safety, safety in people with kidney or liver disease, or safety with other medicines. NAC is also used as a medicine in some settings; ask a pharmacist or clinician before adding it if you take prescription drugs. See medication interactions and talking with a health professional.
References
- GlyNAC Supplementation Improves Glutathione Deficiency, Oxidative Stress, Mitochondrial Dysfunction, Inflammation, Aging Hallmarks, Metabolic Defects, Muscle Strength, Cognitive Decline, and Body Composition: Implications for Healthy Aging. The Journal of nutrition, 2021. PubMed abstract. Read 2026-10-22.
- Glutathione and glutathione-dependent enzymes: From biochemistry to gerontology and successful aging. Ageing research reviews, 2023. PubMed abstract. Read 2026-10-22.
- 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. Clinical and translational medicine, 2021. PubMed abstract. Read 2026-10-22.
- 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, 2023. PubMed abstract. Read 2026-10-22.
- A Randomized Controlled Clinical Trial in Healthy Older Adults to Determine Efficacy of Glycine and N-Acetylcysteine Supplementation on Glutathione Redox Status and Oxidative Damage. Frontiers in aging, 2022. PubMed abstract. Read 2026-10-22.
- GlyNAC (Glycine and N-Acetylcysteine) Supplementation in Mice Increases Length of Life by Correcting Glutathione Deficiency, Oxidative Stress, Mitochondrial Dysfunction, Abnormalities in Mitophagy and Nutrient Sensing, and Genomic Damage. Nutrients, 2022. PubMed abstract. Read 2026-10-22.
- Policy Regarding N-acetyl-L-cysteine (FDA guidance, August 2022). U.S. Food and Drug Administration. Read 2026-10-22.
Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.