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Research · Supplements

GlyNAC

Trials from one US group report that GlyNAC raised glutathione and improved oxidative stress, strength and gait speed in older adults, including a 16-week placebo-controlled trial of 24 people. A 2-week trial of 114 older adults by another group found no rise in glutathione over placebo. No trial measured lifespan. Trials reported GlyNAC as well tolerated.

Add to Bio HackChecked 2026-11-09
Status
Glycine and NAC are sold as dietary supplements in the US. NAC is also an FDA-approved prescription drug.
Also called
glycine and N-acetylcysteine, glycine plus NAC, glutathione precursors, cysteine and glycine
Taken for
slowing aging, longer life, glutathione, oxidative stress, mitochondria, muscle strength, walking speed, memory, insulin resistance

Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on

Shown to help3

Reported risks1

What people take it for, and what was found

Shown to help3

Limited

Strength, gait speed and walking

Small trials found better gait speed, strength and walking distance in older adults on GlyNAC, with gains fading after stopping.

The numbers and sources
Effect
In the 16-week trial, GlyNAC and not placebo improved gait speed, muscle strength and six-minute walk distance [3]. In an open-label pilot, 24 weeks of GlyNAC improved strength, gait speed and exercise capacity, and these gains declined 12 weeks after stopping [5].
Population
24 older adults [3]; 8 older adults [5].
Sources
[3], [5]
Caveats
The abstracts report no effect sizes. Both studies are from the same group, and [5] had no placebo.
Limited

Memory and cognition

Small trials without placebo found cognition improved in older adults and people with HIV, with benefits receding after stopping.

The numbers and sources
Effect
Cognition improved over 24 weeks in older adults [5] and over 12 weeks in people with HIV [6], with benefits receding after GlyNAC stopped.
Population
8 older adults [5]; 8 people with HIV and 8 uninfected controls who took no supplement [6].
Sources
[5], [6]
Caveats
Both studies were open-label with no placebo. The abstracts report no effect sizes.
Limited

Mitochondrial function and aging markers

Small trials found better mitochondrial, inflammation and insulin resistance markers in older adults on GlyNAC, all from one research group.

The numbers and sources
Effect
GlyNAC and not placebo improved mitochondrial fatty acid oxidation, inflammation, endothelial function, insulin resistance and multiple aging hallmarks over 16 weeks [3]. The open-label pilot reported similar changes plus lower genomic damage, body fat and waist size [5].
Population
24 older adults [3]; 8 older adults [5].
Sources
[3], [5]
Caveats
Markers measured by one group in small samples.

Mixed results1

Limited

Glutathione levels

Small trials found mixed results: GlyNAC restored glutathione in older adults in studies from one group, while a larger 2-week trial found no rise.

The numbers and sources
Effect
After 2 weeks of cysteine and glycine, older adults' red blood cell glutathione synthesis and concentration rose to levels seen in younger adults, and oxidative stress markers fell [1]. The same was found in adults with uncontrolled type 2 diabetes [2]. In a 16-week placebo-controlled trial, GlyNAC and not placebo corrected glutathione deficiency in older adults [3]. A separate trial found no rise in the glutathione ratio (12.65 against 12.49 on placebo at 7.2 g a day, p = 0.739) or total glutathione (959.6 against 903.5 mg/L, p = 0.278), its primary endpoints. A post-hoc subgroup with high oxidative stress and low baseline glutathione showed a rise [4].
Population
8 older and 8 younger adults [1]; 12 adults with diabetes and 12 controls [2]; 24 older adults randomized to GlyNAC or alanine placebo [3]; 114 healthy adults, mean age 65, at 2.4, 4.8 or 7.2 g a day for 2 weeks [4].
Sources
[1], [2], [3], [4]
Caveats
The sources disagree. Studies [1] to [3] come from one group and are small, and [1] and [2] had no placebo. Most authors of [4] were Nestlé employees.

Claimed, not studied in people1

Untested

Longer life

Not studied in people. In one study from the group behind the human trials, mice given GlyNAC lived 24% longer than control mice.

No study in people. This rests on animal studies.

The numbers and sources
Effect
C57BL/6J mice given GlyNAC lived 24% longer than mice given placebo, with improved glutathione, oxidative stress, mitochondrial and DNA damage measures in heart, liver and kidney [7].
Population
C57BL/6J mice [7].
Sources
[7]
Caveats
One mouse study by the same research group that ran most of the human trials [7][3]. Lifespan has not been measured in people, and the study has not been repeated by another lab.

Doses studied

A placebo-controlled trial compared 2.4, 4.8 and 7.2 g a day of glycine and NAC in a 1:1 ratio for 2 weeks [4]. The other trials gave GlyNAC for 2 weeks [1][2], 12 weeks [6], 16 weeks [3] and 24 weeks [5].

Risks

Mixed results1

LimitedHow often is not known

Long-term use

Mixed results for NAC, one half of GlyNAC: long-term use was linked to lower cancer risk in people with COPD, while in mice with lung tumors it sped tumor growth.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
In a Taiwanese cohort of 91,546 matched people with COPD, long-term NAC use was linked to lower cancer risk than non-use (adjusted HR 0.69, 95% CI 0.66 to 0.72) [8]. In mouse models of lung cancer, NAC in the diet markedly increased tumor progression and shortened survival, by lowering reactive oxygen species, DNA damage and p53 in tumor cells [9]. No study of glycine and NAC together beyond 24 weeks was located.
Population
Adults with COPD in Taiwan's national insurance database [8]. Mice with B-RAF or K-RAS driven lung cancer [9].
Sources
[8], [9]
Caveats
The cohort is observational, so people who took NAC may differ in ways the matching missed [8]. The mouse finding applies to existing tumors and has not been tested in people [9]. Neither study tested glycine.

Checked, no increase found1

Limited

Adverse effects in trials

Limited evidence: GlyNAC was reported as well tolerated for up to 24 weeks in small trials, which gave no adverse event counts.

The numbers and sources
Effect
GlyNAC was reported as well tolerated over 16 weeks [3] and 24 weeks [5]. In the 2-week dose trial, it was well tolerated at up to 7.2 g a day [4].
Population
24 older adults [3]; 8 older adults [5]; 114 healthy older adults [4].
Sources
[3], [5], [4]
Caveats
The abstracts give no adverse event counts. Trials were small and short. Risks of NAC itself are covered on the NAC page.

Claims tested and not found

  1. That GlyNAC raises glutathione in healthy older adults. A 2-week trial of up to 7.2 g a day found no rise in glutathione over placebo in 114 healthy older adults [4].

Sources

  1. Sekhar RV, Patel SG, Guthikonda AP, et al. Deficient synthesis of glutathione underlies oxidative stress in aging and can be corrected by dietary cysteine and glycine supplementation. The American Journal of Clinical Nutrition. 2011. https://doi.org/10.3945/ajcn.110.003483
  2. Sekhar RV, McKay SV, Patel SG, et al. Glutathione synthesis is diminished in patients with uncontrolled diabetes and restored by dietary supplementation with cysteine and glycine. Diabetes Care. 2010. https://doi.org/10.2337/dc10-1006
  3. 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. The Journals of Gerontology: Series A. 2022. https://doi.org/10.1093/gerona/glac135
  4. Lizzo G, Migliavacca E, Lamers D, et al. 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. https://doi.org/10.3389/fragi.2022.852569
  5. 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. Clinical and Translational Medicine. 2021. https://doi.org/10.1002/ctm2.372
  6. Kumar P, Liu C, Suliburk JW, et al. Supplementing Glycine and N-acetylcysteine (GlyNAC) in Aging HIV Patients Improves Oxidative Stress, Mitochondrial Dysfunction, Inflammation, Endothelial Dysfunction, Insulin Resistance, Genotoxicity, Strength, and Cognition: Results of an Open-Label Clinical Trial. Biomedicines. 2020. https://doi.org/10.3390/biomedicines8100390
  7. Kumar P, Osahon OW, Sekhar RV. 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. https://doi.org/10.3390/nu14051114
  8. Yang CC, Chen WM, Shia BC, Wu SY. Impact of long-term N-acetylcysteine use on cancer risk. American Journal of Cancer Research. 2025. https://doi.org/10.62347/vcdj1296
  9. Sayin VI, Ibrahim MX, Larsson E, et al. Antioxidants accelerate lung cancer progression in mice. Science Translational Medicine. 2014. https://doi.org/10.1126/scitranslmed.3007653

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