GlyNAC: NAC and Glycine Together, What the Studies Show

GlyNAC is the combination of glycine and N-acetylcysteine (NAC), two of the three building blocks your cells use to make glutathione, the body's main antioxidant. It has been studied mainly in older adults, where it raised low glutathione. In a 16-week randomized trial, older adults taking 100 mg per kg of body weight of each a day also improved gait speed and muscle strength compared with placebo.

Key Takeaways

• Glutathione is built from three amino acids: glutamate, cysteine and glycine. NAC supplies cysteine, and glycine is given as is (Kumar et al., 2023).
• In 8 older adults, 2 weeks of cysteine and glycine raised red blood cell glutathione by about 95 percent and lowered oxidative stress markers (Sekhar et al., 2011).
• In a randomized trial of 24 older adults, 16 weeks of GlyNAC improved glutathione, oxidative stress, mitochondrial function, gait speed and strength, while placebo did not (Kumar et al., 2023).
• A 2-week trial in 114 healthy older adults found the biggest glutathione response in people who started with low glutathione and high oxidative stress (Lizzo et al., 2022).
• The trials reported GlyNAC was safe and well tolerated, and the benefits in the pilot study faded after people stopped.

What Is GlyNAC?

GlyNAC is short for glycine plus N-acetylcysteine. The idea behind it is simple: glutathione is made inside cells from glutamate, cysteine and glycine, and older adults in these studies made less of it. The researchers behind GlyNAC found that low glutathione in older adults comes from impaired synthesis, and that older adults had less glycine and cysteine in their red blood cells, so they supplied those two building blocks (Sekhar et al., 2011; Kumar et al., 2023).

Building block	How GlyNAC supplies it
Glutamate	Not added in the trials
Cysteine	Given as NAC, a stable form that releases cysteine
Glycine	Given as glycine itself

For each partner on its own, see our guides to NAC benefits and glycine benefits, and for the finished molecule, glutathione benefits.

The GlyNAC Studies in Older Adults

2011: the first test of the idea

Researchers compared 8 older adults with 8 younger adults. The older group had lower red blood cell glutathione, slower glutathione synthesis and more oxidative stress. After 2 weeks of cysteine and glycine, their glutathione rose by about 95 percent, synthesis sped up, and oxidative stress markers fell to levels no different from the younger group (Sekhar et al., 2011).

2021: the 24-week pilot

In an open-label pilot, 8 older adults took GlyNAC for 24 weeks and were compared with 8 young adults. GlyNAC corrected low red blood cell glutathione and improved oxidative stress, mitochondrial function, strength, gait speed, exercise capacity and scores on cognitive tests. Most of these gains declined during 12 weeks off, and GlyNAC was well tolerated (Kumar et al., 2021).

2023: the randomized, placebo-controlled trial

This is the strongest GlyNAC study so far. Twenty-four adults aged 61 to 80 were randomly assigned to GlyNAC or a placebo of the amino acid alanine for 16 weeks, and 12 adults aged 21 to 40 took GlyNAC for 2 weeks. The older GlyNAC group improved glutathione, oxidative stress, mitochondrial function, inflammation markers and physical function. Gait speed rose to levels no different from the young adults, upper and lower body strength increased, and 6-minute walk distance trended upward. No improvements were seen with placebo, and the authors reported GlyNAC was safe and well tolerated (Kumar et al., 2023).

2022: a shorter trial in healthy older adults

A separate team gave 114 healthy older adults (average age 65) a placebo or glycine and NAC in a 1:1 ratio at 2.4, 4.8 or 7.2 g a day for 2 weeks. Across the whole group, glutathione did not change more than with placebo. In people who started with high oxidative stress and lower glutathione, the medium and high doses raised glutathione in a follow-up analysis. GlyNAC was safe and well tolerated (Lizzo et al., 2022).

Read together, the studies suggest GlyNAC does the most for people whose glutathione is low to begin with, and that changes in strength and walking speed were seen over months rather than days.

GlyNAC Dosage: What the Trials Used

Study	Who	Amount	How long
Sekhar, 2011	8 older adults	Cysteine and glycine	2 weeks
Kumar, 2021 (pilot)	8 older adults	Glycine and NAC	24 weeks, then 12 weeks off
Kumar, 2023 (randomized)	24 adults aged 61 to 80	100 mg per kg a day each of glycine and NAC	16 weeks
Lizzo, 2022	114 healthy older adults	2.4, 4.8 or 7.2 g a day, 1:1 ratio	2 weeks

At 100 mg per kg, a 70 kg (154 lb) adult would take about 7 g of glycine and 7 g of NAC a day, which is how the 2023 trial dosed it, in capsules. These are research amounts given under study supervision rather than a set recommendation, and there is no official GlyNAC dose.

Food Sources of the Building Blocks

All three building blocks of glutathione are amino acids, so protein foods such as eggs, poultry, fish, meat, dairy and legumes supply them. The 2011 study described its approach as dietary cysteine and glycine supplementation (Sekhar et al., 2011). Our guide to glutathione foods covers which foods help most.

Taking NAC and Glycine Together

Most people tolerate NAC and glycine well, and every GlyNAC trial above reported the combination as safe and well tolerated. A few practical points:

• Consistency matters: the strength and walking results came after 16 to 24 weeks, and the pilot's gains faded after stopping.
• Timing: NAC can be taken any time of day. Glycine is often taken in the evening, since it is also studied for sleep; see glycine for sleep.
• Smell: NAC contains sulfur, so a mild sulfur smell is normal.
• Check first: if you take prescription medicine or are pregnant or breastfeeding, talk with your clinician before starting.

Who Might Choose Which

• NAC on its own: for daytime antioxidant support through glutathione.
• Glycine on its own: for an evening routine, since glycine is also studied for sleep quality.
• NAC and glycine together: for people who want to supply both building blocks the GlyNAC trials used, such as NAC in the morning and glycine at night.

Where Our NAC Nasal Spray Fits

Our NAC Nasal Spray gives 50 mg of N-acetylcysteine in every 2-spray serving, with alkaline water as the only other ingredient, made with third-party tested ingredients. It is absorbed through the lining of the nose, so some of each dose skips digestion, and it has no sulfur-tasting capsules to swallow. It is a measured daily amount rather than a copy of the gram doses in the trials, and it is part of our Focus Stack. Benefits build with consistent daily use: months 1 to 2 can bring early changes, and 3 months and beyond is where the full benefit builds.

For the glycine side, our Melatonin-Free Sleep Powder is coming soon. It will give 3 g of glycine with tart cherry, 200 mg of magnesium, myo-inositol and apigenin, mixed in water 30 to 60 minutes before bed, with no added melatonin. Join the waitlist to hear when it launches. Learn more on our NAC ingredient page, our glycine ingredient page and our cellular energy guide.

Frequently Asked Questions

What is GlyNAC?

GlyNAC is glycine plus N-acetylcysteine (NAC), two of the three building blocks of glutathione. It has been studied mainly in older adults with low glutathione.

What are the benefits of NAC and glycine together?

In older adults, GlyNAC raised low glutathione and lowered oxidative stress. In a 16-week randomized trial it also improved gait speed and muscle strength compared with placebo.

What is the GlyNAC dosage used in studies?

The 2023 randomized trial used 100 mg per kg of body weight a day of each, about 7 g of each for a 70 kg adult. A 2022 trial used 2.4 to 7.2 g a day in total, in a 1:1 ratio.

Can I take NAC with glycine?

Yes. That is exactly what the GlyNAC trials tested, and they reported the combination as safe and well tolerated. Check with your clinician first if you take prescription medicine.

When should I take NAC and glycine?

NAC works any time of day. Many people take glycine in the evening because it is also studied for sleep.

How long does GlyNAC take to work?

Glutathione rose within 2 weeks in the first study, while strength and walking changes were measured after 16 to 24 weeks. In the pilot, the benefits faded after 12 weeks off.

Is GlyNAC the same as glutathione?

No. GlyNAC supplies two building blocks so your cells can make more of their own glutathione. See NAC vs glutathione for the difference.

Does GlyNAC work for younger people?

The trials focused on older adults. A 2022 trial found the biggest glutathione response in people who started with low glutathione and high oxidative stress.

Sources

• 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. American Journal of Clinical Nutrition, 2011. https://pubmed.ncbi.nlm.nih.gov/21795440/
• 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://pubmed.ncbi.nlm.nih.gov/33783984/
• 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. Journals of Gerontology Series A, 2023. https://pubmed.ncbi.nlm.nih.gov/35975308/
• 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

These statements have not been evaluated by the Food and Drug Administration. This content is for education and is not medical advice. Our products are not intended to diagnose, treat, cure or prevent any disease. Talk with a healthcare provider before starting a new supplement if you are pregnant, breastfeeding or taking medication.