GlyNAC: A Two-Supplement Combination That Fixed 7 Aging Hallmarks in a Double-Blind Trial
Key Takeaways
- A double-blind, placebo-controlled Baylor trial gave older adults GlyNAC (glycine + N-acetylcysteine) for 16 to 24 weeks and found improvements across 11 aging markers
- Glutathione deficiency corrected by 164%; oxidative stress, mitochondrial dysfunction, inflammation, insulin resistance, and endothelial dysfunction all improved
- Physical function improved significantly: gait speed, grip strength, and 6-minute walk distance
- Cognitive function improved; genomic damage markers decreased
- Benefits reversed within 12 weeks of stopping supplementation
- Important caveat: 24 older adults is a small trial — replication in larger populations is needed
The Problem GlyNAC Targets
Aging is not one thing. It is a collection of biological changes that accumulate simultaneously across multiple systems. Most supplements target one or two of these hallmarks. None of the common longevity compounds have been shown in a single randomized trial to address a large fraction of them simultaneously.
That is what makes the GlyNAC research from Baylor College of Medicine unusual. The compound is not exotic. GlyNAC is simply two amino acids taken together: glycine and N-acetylcysteine (NAC). Both are available over the counter. Both are inexpensive. And both target a specific aging vulnerability that most people have never heard of: glutathione deficiency.
What Glutathione Does and Why It Falls With Age
Glutathione is often called the body’s master antioxidant. Your liver synthesizes it, and virtually every cell in your body uses it to neutralize reactive oxygen species, support mitochondrial function, regulate inflammation, and protect DNA from oxidative damage.
In young adults, glutathione levels are high and tightly regulated. Starting in the 40s, levels begin to decline. By the time someone is in their 70s, glutathione levels in blood and tissues are typically 30 to 50 percent lower than in young adults. The reason is not that the body stops caring about glutathione. It is that production slows because two key building block amino acids become limiting: glycine and cysteine.
Glycine production declines with age. Cysteine is conditionally essential and often inadequate in the diets of older adults. Without sufficient glycine and cysteine, the body cannot produce enough glutathione, regardless of how well everything else is working.
Here is the counterintuitive part: you cannot fix glutathione deficiency by taking glutathione supplements. Oral glutathione is poorly absorbed — the digestive system breaks it down before it can enter circulation intact. The way to raise cellular glutathione is to give the body the raw materials to make more of it. That is exactly what GlyNAC does.
The Baylor Trial
Rajagopal Sekhar and colleagues at Baylor College of Medicine conducted a randomized, double-blind, placebo-controlled study enrolling 24 older adults (average age 74) and 12 young adults (average age 24) for comparison. Older adults received either GlyNAC or placebo for 16 weeks, then supplementation continued for 24 weeks in total for a subset. Published in the Journal of Gerontology, the trial measured 11 different markers of aging at baseline, 2 weeks, 16 weeks, 24 weeks, and after a 12-week washout.
The dose was body-weight-based: glycine at 1.33 millimoles per kilogram per day and NAC at 1.33 millimoles per kilogram per day. For a 70 kg adult, this is approximately 7 to 9 grams of glycine and 6 to 8 grams of NAC per day.
What the Trial Found
Glutathione: Corrected by 121% above baseline at 2 weeks, reaching 164% improvement at 16 weeks. In practical terms, glutathione levels in older participants approached those of the young adult comparison group.
Oxidative stress: Markers of oxidative damage to lipids and DNA decreased significantly. Mitochondrial function: Muscle mitochondrial fatty acid oxidation improved — the measure of how efficiently cells produce energy, which declines substantially with age.
Inflammation: Circulating levels of pro-inflammatory cytokines including TNF-alpha and IL-6 improved. Insulin resistance: Measured by HOMA-IR, insulin resistance improved significantly relative to placebo. Endothelial dysfunction: Flow-mediated dilation improved, indicating better blood vessel function.
Physical function: Gait speed, grip strength, and 6-minute walk distance all improved in the GlyNAC group. These are validated clinical measures of functional aging used to predict falls, disability, and mortality.
Cognitive function: The GlyNAC group showed improvements on cognitive testing. Genomic damage: Markers of DNA strand breaks decreased. Body composition: Waist circumference decreased.
When participants stopped taking GlyNAC, the benefits began reversing within 12 weeks. This suggests the effects are dependent on continued supplementation, not a permanent correction.
Why This Combination Works
The research from Baylor proposes a cascade mechanism: aging causes glycine and cysteine to become deficient, which causes glutathione deficiency, which causes oxidative stress, which damages mitochondria, which impairs energy production, which accelerates inflammation, insulin resistance, physical decline, and cellular aging.
GlyNAC interrupts this cascade at the root. By restoring the building blocks for glutathione synthesis, the rest of the downstream effects partially correct themselves. This is different from taking individual antioxidants like vitamin C or E, which scavenge reactive oxygen species after they are produced. GlyNAC corrects the upstream production failure that allows oxidative stress to accumulate in the first place.
The Caveats
The trial enrolled 24 older adults. This is a small sample by the standards of clinical medicine. The results across 11 markers are striking, but replication in larger, independent trials is essential before drawing firm conclusions.
The dose used in the trial is higher than what many commercial GlyNAC products contain. The body-weight-based dose translates to roughly 7 to 9 grams of glycine and 6 to 8 grams of NAC per day for an average adult. Some commercially available products contain significantly less.
The trial tracked surrogate biomarkers of aging, not disease outcomes or mortality. We do not yet know whether correcting glutathione deficiency with GlyNAC reduces rates of heart disease, cancer, dementia, or all-cause mortality over long periods. NAC at high doses has been associated with gastrointestinal side effects in some individuals.
On the positive side: the USC Longevity Institute ran an independent double-blind RCT in 2025 that appears to have confirmed the core GlyNAC findings in a broader older-adult population. Across three independent human trials, the same core findings replicate: GlyNAC corrects glutathione deficiency, reduces oxidative stress, and improves mitochondrial function in older adults. That is more replication than most longevity supplements have.
What You Can Realistically Do Now
GlyNAC is genuinely unusual in the supplement world because it targets a specific, measurable, age-related deficiency rather than claiming a general benefit. Glutathione deficiency in older adults is real, measurable, and consistently documented across studies. The mechanism by which GlyNAC corrects it is well understood.
If you are over 60 and interested in trying GlyNAC based on this evidence: take glycine and NAC together — separately or as a combined product. The trial dose was approximately 7 to 9 grams of glycine and 6 to 8 grams of NAC per day. Lower doses may still provide partial benefit. Starting with 1 to 3 grams of glycine and 600 to 1,200 mg of NAC is a more conservative starting point. Both compounds are generally well tolerated. Glycine is cheap, mildly sweet, and dissolves easily in water. NAC is widely sold in 600 mg capsules.
The Bottom Line
A double-blind, placebo-controlled trial at Baylor College of Medicine found that GlyNAC supplementation in older adults corrected glutathione deficiency and improved 11 different markers of biological aging over 24 weeks, including mitochondrial function, inflammation, physical performance, cognitive function, and DNA integrity. The effects reversed after stopping supplementation. The trial was small. Larger replication trials are ongoing. But the mechanism is sound, the compounds are safe and inexpensive, and no other simple supplement combination has shown this breadth of biological effect in a controlled human trial.
FAQ
What is GlyNAC made of?
GlyNAC is a combination of glycine (a non-essential amino acid) and N-acetylcysteine (NAC, a form of the amino acid cysteine). Together they provide the two key precursors the body needs to synthesize glutathione.
Can I take NAC without glycine?
You can, but the research on aging hallmarks specifically studied the combination. NAC alone provides cysteine but not glycine, and older adults are typically deficient in both. The combination is theorized to be more effective at raising glutathione than either alone.
Is GlyNAC the same as taking glutathione?
No. Oral glutathione supplements have poor bioavailability because the digestive system breaks them down. GlyNAC provides the building blocks for your body to synthesize glutathione itself, which is more effective at raising intracellular levels.
What dose should I take?
The Baylor trial used body-weight-based dosing equating to roughly 7 to 9 grams of glycine and 6 to 8 grams of NAC per day for a 70 kg adult. Many commercial products contain less. Starting with 1 to 3 grams of glycine and 600 to 1,200 mg of NAC is a more conservative starting point.
Are there any side effects?
NAC at high doses above 1,800 mg per day has caused nausea and GI discomfort in some studies. Glycine is generally extremely well tolerated. The Baylor trial reported GlyNAC to be safe and well tolerated throughout the study period.
How quickly do you see effects?
The Baylor trial showed significant glutathione correction within 2 weeks. Physical performance improvements were measured at 16 weeks. Benefits begin to reverse within 12 weeks of stopping.
References
- Sekhar RV, 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 Jan 26;78(1):75-89. PMID: 35975308. pubmed.ncbi.nlm.nih.gov/35975308
- 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, Insulin Resistance, Endothelial Dysfunction, Genotoxicity, Muscle Strength, and Cognitive Decline. Clin Transl Med. 2021 Mar;11(3):e372. PMID: 33783984. pubmed.ncbi.nlm.nih.gov/33783984
- Lopez-Otin C, Blasco MA, Partridge L, et al. Hallmarks of aging: An expanding universe. Cell. 2023 Jan 19;186(2):243-278. PMID: 36599349. pubmed.ncbi.nlm.nih.gov/36599349
