GlyNAC: Benefits, Dosage and What Trials Show

Quick answer

GlyNAC, in short: GlyNAC is simply two supplements taken together, glycine and NAC (N-acetylcysteine). A larger trial of 114 healthy older adults missed its main goal: it did not raise the main glutathione measure [1]. The more positive results come from two small trials by one research group, with 8 and 24 older adults [2][3]. We rate the evidence D: small trials with mixed signals, and nothing yet that shows it helps people live longer or stay healthier.

What is GlyNAC?

Glycine is an amino acid, and NAC is a form of the amino acid cysteine. The body needs glycine and cysteine to make glutathione, an antioxidant [1]. The researchers behind GlyNAC suggest that low glutathione may play a role in aging [3]. “GlyNAC” is the name researchers gave to the pair. You can read about each part in our glycine and NAC entries.

GlyNAC benefits: what might it help with?

Possible benefit	Rating	In plain words
Raising glutathione in healthy older adults	Mixed	The larger 114-person trial missed its main goal. A later subgroup analysis, chosen after the results were in, looked positive [1]
Markers of oxidative stress, inflammation and mitochondria (cell energy)	Early	Small trials from one group reported improvements. These are lab markers, not health results [2][3]
Strength, walking speed and fitness in older adults	Early	Reported in two small trials from the same group [2][3]. Needs testing by independent teams
Living longer	Early (animal or lab only)	Mice given GlyNAC lived about 24% longer. No human trial has tested this [4]

Ratings describe how good the research is, not a promise that it will work for you.

What the research says

• The larger trial that missed its main goal (114 healthy older adults, 2 weeks). People took 2.4, 4.8 or 7.2 g a day of GlyNAC, or a placebo, for 2 weeks. The main goal was to raise glutathione, and it did not (p = 0.278 for total glutathione). The authors then ran post hoc analyses (done after the main result was known). In a subset with high oxidative stress and low glutathione to begin with, the medium and high doses were linked to more glutathione being made. That subgroup result is exploratory. Most of the authors work for Nestlé, and its health-science arm holds patents on, and sells, glycine and NAC products [1]. PubMed · DOI
• 24 older adults, 16 weeks. In a randomized trial, 12 older adults took GlyNAC and 12 took a placebo. The authors reported improvements in glutathione, oxidative stress, inflammation, physical function and other markers, and said GlyNAC was safe and well tolerated [3]. It is small, and the authors are the same group as the 2021 pilot below. PubMed · DOI
• 2021 pilot (8 older adults). This open-label trial had no placebo group. GlyNAC was taken for 24 weeks and then stopped for 12. The authors reported improvements while on it, but the benefits declined after stopping [2]. PubMed · DOI
• Mouse study. In mice, GlyNAC was linked to a 24% longer life [4]. This is animal research, and it does not tell us what happens in people. PubMed · DOI
• 2026 review. It calls GlyNAC a “proof-of-concept” and notes that NAC’s effects depend on a person’s starting glutathione level, with inconsistent results in healthy people [5]. PubMed · DOI

The main limits: the positive human trials are tiny and come from one research group, and the biggest trial was run with company involvement and did not meet its main goal.

Amounts and how people take it

These are amounts used in studies, not recommendations.

• Larger trial: 2.4, 4.8 or 7.2 g a day (glycine and NAC in a 1:1 ratio) for 2 weeks, in healthy adults with an average age of 65 [1].
• 2021 pilot: doses were set by body weight, 1.33 mmol/kg/day of glycine and 0.81 mmol/kg/day of cysteine given as NAC, for 24 weeks [2].
• 16-week trial: we did not verify the dose, because the abstract doesn’t state it [3].

GlyNAC dosage for seniors

All the human trials we found were in older adults, so the doses above are the ones studied in that group. We can’t recommend a dose, and we found no trial that tested which dose works best.

GlyNAC vs NAC alone

We found no trial that compared GlyNAC with NAC alone, so we can’t say whether adding glycine makes a difference. A 2026 review notes that NAC on its own had inconsistent results in healthy people [5]. See our NAC entry for NAC’s own side effects and cautions.

Side effects, interactions and who should check first

The authors of the larger trial and of the 16-week trial reported that GlyNAC was safe and well tolerated [1][3]. These trials were short and small, so rare or long-term problems could be missed.

Who should check with a doctor or pharmacist first

Check with a doctor or pharmacist first if you:

• take any regular medicine, because we found no interaction data for the combination
• are pregnant or breastfeeding, or planning to be, because we found no safety data for this group
• have a long-term condition, especially kidney or liver problems, because the trials were in generally healthy older adults
• are thinking of more than the amounts used in studies

Where to buy

Look for a label that lists the amount of glycine and of NAC in grams or milligrams per serving, and a stated third-party testing certificate you can check. Work out the price per daily dose rather than comparing pack prices. Because the trial doses are in grams, a product with a small serving may supply far less than the trials used.

FAQ

What is GlyNAC?

GlyNAC is the combination of glycine and N-acetylcysteine (NAC), two building blocks the body uses to make the antioxidant glutathione [3]. It isn’t a single new ingredient: it is two supplements taken together, and the name was given to the pair by the researchers who tested it.

Does GlyNAC work?

The evidence is mixed. Two small trials from one group reported improvements in older adults [2][3], but a larger trial of 114 healthy older adults missed its main goal [1]. We rate the evidence D, so it is not proven to help.

What GlyNAC dosage do studies use, including for seniors?

The human trials we found were all in older adults. The larger trial, with an average age of 65, tested 2.4, 4.8 and 7.2 g a day for 2 weeks [1], and the 2021 pilot set doses by body weight [2]. These are amounts used in studies, not recommendations.

What are the side effects of GlyNAC?

The authors of the larger trial and the 16-week trial reported it was safe and well tolerated [1][3]. The trials were small and short, so rare or long-term effects are unknown. Our NAC entry lists NAC’s own cautions, and a doctor or pharmacist can advise if you take medicine.

GlyNAC vs NAC: what is the difference?

NAC is one half of GlyNAC. GlyNAC adds glycine, the other building block of glutathione. We found no trial comparing GlyNAC with NAC alone, so we can’t say whether the combination does more [5].

Related pages

• Glycine
• NAC (N-acetylcysteine)
• Our glycine buying guide
• Ergothioneine: another compound studied in aging research
• Longevity supplements for beginners: where this fits in a beginner’s routine
• All supplements A-Z

Talk to your doctor

This page is for general information and is not medical advice. Speak to a doctor or pharmacist before starting any supplement, especially if you are pregnant or breastfeeding, take any medicine, or have a health condition.

References

We cite only studies and official pages we checked against PubMed, the publisher or the agency’s own site. The A to E evidence grades are explained in our editorial policy. See also our medical disclaimer and affiliate disclosure.

1. 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. Front Aging. 2022. PubMed · DOI
2. 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. Clin Transl Med. 2021. PubMed · DOI
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. J Gerontol A Biol Sci Med Sci. 2023. PubMed · DOI
4. 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. PubMed · DOI
5. Wang X, Hou R, Chen Z, et al. Glycine and N-acetylcysteine supplementation, with or without exercise, in brain health and functional aging: implications for sarcopenia and frailty in older adults. Front Nutr. 2026. PubMed · DOI