Supplement
GlyNAC (Glycine + NAC)
Amino acid · Glycine + N-acetylcysteine
GlyNAC is the combination of glycine and N-acetylcysteine, the two scarce building blocks of glutathione. The idea is not to swallow an antioxidant, but to give the aging cell back its raw materials. That the store fills up has been shown with muscle biopsy and placebo — everything beyond that comes from the lab that holds the patent.
In short
Glutathione is the cell’s most important antioxidant and consists of glutamate, cysteine and glycine. Older people have less glycine and cysteine and rebuild glutathione only about half as fast; if the building blocks are given, the store fills up again. This is supported by muscle biopsies and placebo. Everything else — strength, gait, thinking, lifespan — comes from the same lab, rests on 8 to 12 people per group and disappears after stopping. The only independent study was negative, though with less than half the dose.
The mechanism
Glutathione is a trio of glutamate, cysteine and glycine. Cysteine can be supplied as N-acetylcysteine, which has been a medicine for decades as a cough expectorant. GlyNAC is NAC plus glycine.
The basis is a 2011 measurement in 8 older and 8 younger people: the older ones had about half as much glutathione in their red blood cells, 1.12 versus 2.08 millimoles per liter, and rebuilt it half as fast, 45.8 versus 83.1 percent per day. After 2 weeks with both building blocks, their glutathione was 95 percent higher, at the level of the younger ones — open-label and without a control group.
Why not NAC alone
NAC alone is apparently not enough: in 2018, only the combination improved heart function in 30-month-old mice over 7 weeks. Glycine alone extended life by 4 to 6 percent in the Interventions Testing Program, and NAC alone worked at the Jackson Laboratory only in males, presumably because the animals ate less.
The mouse study with the 24 percent
The figure used in advertising comes from 2022: 32 lab mice, 16 with glycine and NAC in their feed from the 65th week of life, 16 without. The control animals lived 104.0 weeks on average, the treated ones 128.6 — about 24 percent longer, in both sexes.
One lab, a small study; the authors name the number of animals as a limitation. In addition: in other labs, around three quarters of the males of this strain are still alive at 24 months. The control group therefore died strikingly early. Whether GlyNAC extended life or the controls were unlucky, the study does not say.
A state, not a remodeling
The 2021 pilot study has an instructive design: 8 older people between 70 and 80 years took GlyNAC for 24 weeks, then stopped for 12 weeks. Gait speed rose from 1.0 to 1.5 meters per second, faster than the 1.4 of the young comparison group, and grip strength from 27.0 to 30.9 kilograms.
After the washout phase, gait was at 1.2 and grip strength at 27.3, and glutathione almost back to baseline. A 2020 study in HIV patients showed the same: benefits gone 8 weeks after stopping. A good sign for the mechanism, a bad one for the word anti-aging.
Houston versus Nestlé
The largest study does not come from Houston but from Nestlé: 114 healthy older people, on average 65 years old, randomized against placebo, 2 weeks. For the primary endpoint, glutathione in the blood, there was no difference, p equal to 0.278.
This does not settle the matter cleanly. The highest Nestlé dose was less than half the Houston amount, the duration was shorter, the participants were younger, and measurements were taken in the blood instead of the muscle. They do not contradict each other cleanly; they measure something different. All positive human data come from the lab with the 2013 patent.
What is well supported
The hard finding is the 2023 randomized study: 24 older people between 61 and 80 years, randomly assigned to two groups of 12 each, GlyNAC or alanine as placebo, over 16 weeks, plus 12 young people for comparison. Measurements were taken by muscle biopsy. Muscle glutathione was 7.0 in the young and 2.4 in the older people before the start; after 16 weeks of GlyNAC it was 6.3 and thus statistically no longer distinguishable from the young, while under placebo it remained unchanged at 2.4. Markers of oxidative stress fell by 72 percent.
What the studies show
Randomized study 2023 — 24 older people, 16 weeks, with muscle biopsy
Randomized, placebo-controlled, funded by the US National Institute on Aging and registered. 24 older people between 61 and 80 years, 12 each on GlyNAC or alanine as placebo, over 16 weeks. In the GlyNAC group, gait speed rose from 1.13 to 1.34 meters per second, grip strength from 32.3 to 36.7 kilograms, and systolic blood pressure fell by 8 points. Under placebo there was no improvement.
Pilot study 2021 — 8 older people, with washout phase
Open-label and without a control group: 8 older people between 70 and 80 years, 24 weeks of intake, then 12 weeks without. Gait speed 1.0, then 1.5, then 1.2 meters per second, young comparison group 1.4; grip strength 27.0, then 30.9, then 27.3 kilograms.
Nestlé study 2022 — 114 healthy older people
The only independent study: 114 healthy older people with an average age of 65, randomized and controlled, three dose levels over 2 weeks. The primary endpoint was total glutathione in the blood; there, no difference from placebo, p equal to 0.278. Only a subgroup formed after the fact, with high oxidative stress and a low baseline value, showed an increase.
Where the data stop
What is supported is the replenishment of glutathione; everything else is thinner. Gait speed, grip strength and blood pressure come from before-and-after comparisons within the groups. The direct comparison between GlyNAC and placebo after 16 weeks is announced in the methods section but not reported in the accessible results table; with 12 people per arm, there is no saying that it would hold.
Then there is the structure of the evidence. All positive human data come from the lab whose university holds the patent; the only independent study was negative on its primary endpoint. And the formula of reversing aging does not hold, because the benefits disappear after stopping. Until someone else repeats this with the full dose, GlyNAC is a good finding and not an anti-aging agent.
Status, approval and legal
In Germany, N-acetylcysteine is an over-the-counter medicine from the pharmacy. In 2022, the US Food and Drug Administration found that NAC had been approved as a drug before it was sold as a supplement and therefore should not actually be one — but it explicitly tolerates its sale. In Germany, the Berlin Regional Court prohibited an NAC powder as a dietary supplement as early as 2010; capsules with gram amounts are a gray area. The 2013 patent is held by Baylor College of Medicine, licensed to Nestlé Health Science and marketed as Celltrient.
Safety
In the Houston studies, no side effects were reported and liver and kidney values remained unremarkable — though in only a few dozen people. Two further points. First, NAC accelerated tumor growth in mice with induced lung cancer; antioxidants also protect cells one does not want to protect. For smokers this is not a side issue. Second, a related 2025 study in 21-month-old mice over 12 weeks found the heart benefit only in males — the females even fared worse under GlyNAC.
BK-Score Hype far ahead of evidence
| Human evidence | 3 | |
|---|---|---|
| Mechanism | 6 | |
| Safety data | 3 | |
| Hype gap | 2 | |
| Track record of use | 3 |
The claim that GlyNAC reverses features of aging goes back to a study with 24 older adults over 16 weeks (Kumar et al., J Gerontol A 2023) – from a single research group, without independent replication. Improvements were seen in glutathione status, oxidative stress, mitochondrial function as well as gait speed and grip strength – the latter, however, as before-and-after comparisons within the groups. That glycine and cysteine feed glutathione synthesis is established human biochemistry; the leap from there to the hallmarks of aging is not. Hard endpoints are missing, as are long-term data beyond 16 weeks.
The score rates the state of knowledge, not the substance. “Safety data 9” means well studied – not harmless.
Subjective assessment by Biohacking Kompakt based on published scoring rules – not a scientific rating and not a medical recommendation. Rules and all ratings (German)
Frequently asked questions about GlyNAC (Glycine + NAC)
What exactly is GlyNAC?
The combination of glycine and N-acetylcysteine. Both are building blocks of glutathione, the cell’s most important antioxidant. The idea is not to supply the finished antioxidant, but the two raw materials that become scarce in old age.
Is it proven that GlyNAC replenishes glutathione?
Yes, that is the hard part of the evidence. In a randomized study over 16 weeks, muscle glutathione in the older people rose from 2.4 to 6.3 and was thus no longer distinguishable from the values of the young at 7.0. Under placebo it remained unchanged at 2.4.
Does GlyNAC also work on strength and walking speed?
The numbers look good but are thinly supported. Gait speed and grip strength rose in the GlyNAC group, but not under placebo. However, these are before-and-after comparisons within the groups with 12 people per arm; the direct group comparison after 16 weeks is not reported in the accessible table.
Does the effect last after stopping?
No. In the pilot study, after 12 weeks without intake, gait speed fell from 1.5 to 1.2 and grip strength from 30.9 to 27.3 kilograms, and glutathione almost to baseline. In an HIV study, the benefits had disappeared 8 weeks after stopping. A deficiency is corrected for as long as one keeps topping up.
Why do the Baylor and Nestlé studies contradict each other?
They do not measure the same thing. The Nestlé study with 114 participants ran for 2 weeks, tested a dose of less than half, included younger participants and measured glutathione in the blood instead of the muscle. Its primary endpoint was negative, with a p-value of 0.278. It remains notable that all positive data come from the lab with the patent.
Are there risks?
Three should be mentioned. No side effects were reported in the studies, though in only a few dozen people. NAC accelerated tumor growth in mice with induced lung cancer, which is relevant above all for smokers. And in a 2025 mouse study only the males benefited, while the females fared worse under GlyNAC.
The podcast episode (in German)
Episode 65
Glutathione: the master antioxidant fact-checked
The podcast by Paul Höser (Episode 65) · with Paul & Paula. The GlyNAC study in detail: glutathione in older people back to youthful levels, less oxidative stress, better mitochondria and walking speed (Sekhar, Baylor College). Information only, no dosage or usage recommendation.
Related
- Works together withGlycine
- Works together withNAC (N-acetylcysteine)
- Works together withAlpha-Lipoic Acid (ALA)
- Same categoryAcetyl-L-carnitine (ALCAR)
- Same categoryAmino acids (EAA & BCAA)
- Same categoryTaurine
- Same goal: anti-aging / longevityNMN
- Same goal: anti-aging / longevityGlutathione
- Same goal: anti-aging / longevityAstragalus & Cycloastragenol (TA-65)
- Same goal: anti-aging / longevityCa-AKG (calcium alpha-ketoglutarate)
- Same goal: anti-aging / longevityPQQ
- Same goal: anti-aging / longevityErgothioneine
Sources
- Sekhar et al., Am J Clin Nutr 2011
- Kumar et al., Clin Transl Med 2021 (pilot study with washout phase)
- Kumar et al., J Gerontol A 2023 (randomized study with muscle biopsy)
- Kumar et al., Nutrients 2022 (lifespan in mice)
- Lizzo et al., Front Aging 2022 (independent study)
- Miller et al., Aging Cell 2019 (glycine in the ITP)
- Sayin et al., Sci Transl Med 2014 (antioxidants and lung cancer)
- Angelini et al., J Gerontol A 2025 (sex difference in the heart)
Open in the database – with search, filters and comparison (German app)
Information only, not medical advice and not a usage or dosage recommendation. Prescription-only and unapproved substances belong in the hands of a physician. Last updated: 2026-09-13.