GlyNAC (Glycine + N-Acetylcysteine)
Summary
GlyNAC pairs glycine with NAC to raise glutathione. One Baylor group reported that older adults had higher glutathione, less oxidative stress and better strength and walking speed after 16–24 weeks (grade C). A 114-person Nestlé trial found no rise in glutathione after 2 weeks at up to 7.2 g/day. Trials are small, and NAC has a special FDA status.
Key facts
- Glutathione and oxidative stress in older adults (mixed, C); physical function (D, one research group); insulin resistance in type 2 diabetes (D)[2][5][3][4]
- 2.4, 4.8 or 7.2 g/day (1:1) for 2 weeks in the largest trial; weight-based doses in the Baylor trials[5][2]
- FDA says NAC is excluded from the dietary supplement definition but is using enforcement discretion for most NAC supplements[1]
- The negative 2-week trial was run by Nestlé, which holds patents and licenses for glycine plus NAC and sells GlyNAC products[5]
- 6 graded human outcomes on this page
- October 10, 2026
How it works
ProposedGlutathione is made from glycine, cysteine and glutamate. NAC supplies cysteine; older adults in small studies had low red-cell glycine, cysteine and glutathione and slower glutathione synthesis, which supplementing glycine and cysteine raised.[6][2]
What the human research says
Human trials only, one row per outcome. The form column shows what each trial actually tested. Grades follow our evidence-grading policy.
At a glance: strongest evidence per outcome
| Outcome | Grade | Effect | Strongest evidence | Rows |
|---|---|---|---|---|
| Glutathione | Grade C | No effect | RCT · n = 114 · 2022 | 2 rows |
| Aging | Grade C | Improved | Pilot RCT · n = 36 · 2023 | 2 rows |
| Insulin sensitivity | Grade D | Improved | Open-label · n = 20 · 2022 | 1 row |
| HIV | Grade D | Improved | Open-label · n = 16 · 2020 | 1 row |
Every graded row
| Outcome | Effect | Grade | Best evidence | PMID |
|---|---|---|---|---|
| Blood glutathione in healthy older adults | No effect | Grade C | RCT · n = 114 · 2022 Healthy older adults (mean age 65) Form: Glycine plus N-acetylcysteine (1:1) · Dose: 2.4, 4.8 or 7.2 g/day · Duration: 2 weeks GlyNAC was safe and well tolerated but did not raise total glutathione (the primary endpoint) or the reduced-to-oxidized glutathione ratio compared with placebo; the abstract reports a post-hoc benefit only in a subgroup with higher oxidative stress or lower baseline glutathione. | 35821844 (opens PubMed)Source [5] |
| Glutathione, oxidative stress and physical function in older adults | Improved | Grade C | Pilot RCT · n = 36 · 2023 24 older adults randomized (GlyNAC or alanine placebo) plus 12 young adults Form: Glycine plus N-acetylcysteine · Dose: Dose not stated in the abstract · Duration: 16 weeks (young adults 2 weeks) GlyNAC, but not placebo, improved glutathione deficiency, oxidative stress, mitochondrial function, inflammation, insulin resistance, gait speed, strength, waist size and systolic blood pressure in older adults; it was safe and well tolerated. | 35975308 (opens PubMed)Source [2] |
| Insulin resistance and fat burning in type 2 diabetes | Improved | Grade D | Open-label trial · n = 20 · 2022 10 adults with type 2 diabetes and 10 unsupplemented controls Form: Glycine plus N-acetylcysteine · Dose: Dose not stated in the abstract · Duration: 14 days Before supplementation the diabetes group had lower mitochondrial fat oxidation and much higher insulin resistance; the authors report that 14 days of GlyNAC improved these measures. | 35052658 (opens PubMed)Source [4] |
| Glutathione, strength, gait speed and cognition | Improved | Grade D | Open-label trial · n = 16 · 2021 8 older adults and 8 young adults Form: Glycine plus N-acetylcysteine · Dose: Dose not stated in the abstract · Duration: 24 weeks, then 12 weeks off In older adults GlyNAC corrected red-cell glutathione deficiency and lowered oxidative stress, with reported gains in strength, gait speed, cognition and body composition; benefits declined after stopping for 12 weeks. | 33783984 (opens PubMed)Source [3] |
| Glutathione synthesis in older adults | Improved | Grade D | Open-label trial · n = 16 · 2011 8 older and 8 younger adults Form: Cysteine (as NAC) plus glycine · Dose: Dose not stated in the abstract · Duration: 2 weeks Supplementation raised red-cell glutathione concentration by 94.6% and its fractional synthesis rate by 78.8% in older adults, and lowered markers of oxidative stress to levels similar to younger adults. | 21795440 (opens PubMed)Source [6] |
| Oxidative stress and physical function in people with HIV | Improved | Grade D | Open-label trial · n = 16 · 2020 8 people with HIV and 8 uninfected controls Form: Glycine plus N-acetylcysteine · Dose: Dose not stated in the abstract · Duration: 12 weeks, then 8 weeks off The authors report improvements in oxidative stress, mitochondrial function, inflammation and other measures after 12 weeks in people with HIV. | 33007928 (opens PubMed)Source [7] |
Forms
| Form | Elemental % | Absorption (human data) | GI tolerance | Studied for |
|---|---|---|---|---|
| Glycine plus NAC, 1:1 by weight | Varies[5] | Did not raise blood glutathione over 2 weeks at up to 7.2 g/day in healthy older adults.[5] | Safe and well tolerated at 2.4–7.2 g/day for 2 weeks.[5] | Nestlé dose-ranging trial |
| Weight-based glycine plus NAC (Baylor protocol) | Varies[2][3] | Raised red-cell glutathione in older adults in the Baylor studies.[6][3] | Reported safe and well tolerated over 16 weeks.[2] | Aging, type 2 diabetes and HIV studies |
| Glycine and NAC bought separately | Varies[8][1] | No separate absorption data in our sources.[8] | No data for self-combined products in our sources.[8] | Not studied as a separate product |
Studied doses
Doses studied in human trials ranged from 2.4 to 7.2 g/day (1:1 glycine to NAC) for 2 weeks in the largest trial; the Baylor trials used weight-based doses for 2 to 24 weeks that are not stated in their abstracts.[5][2][3]
Interactions
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
Who should be careful
- People taking prescription NAC or nitroglycerin
- GlyNAC contains NAC, which is also a drug ingredient; check with a clinician before combining with prescription products.[1]
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.
Safety
GlyNAC was reported safe and well tolerated in trials of 2 to 24 weeks.
- Tolerance
- Both the Baylor 16-week trial and the 2-week Nestlé trial reported GlyNAC as safe and well tolerated.[2][5]
- Trial size
- The longest controlled trial gave GlyNAC to only 12 older adults.[2]
- Regulatory
- NAC sold as a supplement sits under FDA enforcement discretion rather than full dietary supplement status.[1]
How to read the label
- Label dose vs clinical doseThe largest trial tested 2.4–7.2 g/day of combined glycine and NAC; check how much of each a product contains.[5]
- NAC statusFDA does not consider NAC a lawful dietary ingredient but is not acting against most NAC supplements under its 2022 enforcement policy.[1]
- Brand claimsMarketing often cites the Baylor trials; the Nestlé trial in 114 people did not confirm a glutathione rise.[2][5]
Cost per studied dose, without the sales pitch
Compare any product you already have by the amount it delivers, not by capsule count or front-of-pack weight.
Cost per studied dose
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Frequently asked questions
Does GlyNAC raise glutathione?
The Baylor studies reported large rises in red-cell glutathione in older adults, but a 114-person Nestlé trial found no rise in blood glutathione after 2 weeks.[6][2][5]
Does GlyNAC slow aging?
A 16-week trial in 24 older adults reported improvements in many aging markers, strength and walking speed, but only 12 people took GlyNAC.[2]
What dose of GlyNAC was studied?
The largest trial tested 2.4, 4.8 and 7.2 g/day of glycine and NAC in a 1:1 ratio.[5]
Is NAC legal in supplements?
FDA says NAC is excluded from the dietary supplement definition but is exercising enforcement discretion for most NAC supplements.[1]
Sources
- [1]Guidance for Industry: Policy Regarding N-acetyl-L-cysteine (final, August 2022). U.S. Food and Drug Administration, 2022. guideline
- [2]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. pilot-RCT
- [3]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. open-label
- [4]GlyNAC (Glycine and N-Acetylcysteine) Supplementation Improves Impaired Mitochondrial Fuel Oxidation and Lowers Insulin Resistance in Patients with Type 2 Diabetes: Results of a Pilot Study.. Antioxidants (Basel), 2022. open-label
- [5]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. RCT
- [6]Deficient synthesis of glutathione underlies oxidative stress in aging and can be corrected by dietary cysteine and glycine supplementation.. Am J Clin Nutr, 2011. open-label
- [7]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. open-label
- [8]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.. J Nutr, 2021. review
What changed
- First draft. Every PMID checked against NCBI E-utilities esummary (title and year taken from the record) and abstracts read for the cited rows.
- Adversarial review pass: every evidence row re-read against its PubMed abstract. Official source opened before citing: FDA Guidance for Industry: Policy Regarding N-acetyl-L-cysteine (final, August 2022; page content current as of 08/01/2022). No NIH ODS, NCCIH or EFSA monograph covers GlyNAC. Industry ties: the Nestlé dose-ranging trial (Nestlé employees; Nestlé Health Science holds patents and licenses for glycine plus NAC; Profil received Nestlé funding); Baylor trials funded by the NIA and a McNair Foundation gift, with authors reporting no conflicts. Animal studies (mouse lifespan, brain) were not used for claims. Retraction, expression-of-concern, erratum and withdrawn checks on all 7 PMIDs: none flagged. Page set indexable. Independent browser review (4 parallel reviewers, every evidence row checked against its abstract and official sources on the Vercel preview) found issues that were fixed: evidence direction now follows the site convention (up = improved, down = worsened), plus wording and disclosure corrections listed in the batch-14 PR review comment.