Short answer: GlyNAC is a combination of glycine and N-acetylcysteine (NAC), two building blocks your body uses to make the antioxidant glutathione. A small 16-week trial in older adults found improvements in glutathione, inflammation markers and physical function. A larger two-week trial missed its main goal. The trial doses were also much higher than most supplements provide. Promising, but not yet proven.
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| Quick facts |
|
| What it is |
Glycine + N-acetylcysteine (NAC) |
| Why |
Both are needed to make glutathione, which tends to fall with age |
| Best human evidence |
One small 16-week RCT in 24 older adults (Kumar et al., 2023) |
| Trial dose |
100mg/kg of each per day (about 7g of each for a 70kg adult) |
| Typical supplement dose |
2g glycine + 2g NAC per day |
| Safety |
Generally well tolerated; NAC has a strong sulphur smell |
What Is GlyNAC?
Glutathione is one of the body’s main antioxidants. Levels tend to fall with age, and supplementing glutathione directly isn’t well absorbed. GlyNAC supplies two of its three building blocks: glycine, and cysteine from NAC. The idea, developed by researchers at Baylor College of Medicine, is that older adults run short of these and that topping them up restores glutathione production.
What Does the Research Show?
In a 2023 randomised, placebo-controlled trial, 24 older adults aged 61–80 took GlyNAC or placebo for 16 weeks. The GlyNAC group showed improvements in glutathione levels, oxidative stress, mitochondrial function, inflammation, insulin resistance, gait speed, muscle strength and 6-minute walk distance. 12 younger adults also took GlyNAC for two weeks for comparison.
That’s a broad and impressive list, but the trial was very small, all participants had a BMI over 27, and it came from a single research group. Aeternum’s own product page also mentions a larger two-week trial that didn’t improve its primary glutathione outcome overall. Treat GlyNAC as promising, not proven.
Dose matters: the trial used 100mg per kg of body weight of each ingredient. For a 70kg adult that’s roughly 7g of glycine plus 7g of NAC a day. Aeternum’s labelled serving is 2g of each, about a third of the trial dose. Don’t raise your dose to trial levels without medical advice.
GlyNAC Side Effects and Safety
Glycine and NAC have long safety records as individual supplements. NAC can cause nausea, digestive upset and, rarely, allergic reactions, and it has a strong sulphur smell and taste. NAC may interact with nitroglycerin and some blood pressure medicines.
Speak with a healthcare professional first if you:
- take nitroglycerin, blood pressure medicines or blood thinners
- have asthma (NAC can rarely trigger bronchospasm)
- are pregnant or breastfeeding
- have kidney disease
Where to Buy GlyNAC
Aeternum sells GlyNAC Powder: 120g (30 servings of 2g glycine + 2g NAC) for £27, about £0.90 a day. That’s a UK display price on 14 November 2026. Subscribers get 20% off. Aeternum’s GlyNAC capsules are sold out until around December 2026.
What Glutathione Does and Why It Falls With Age
Glutathione is made inside your cells from three amino acids: glycine, cysteine and glutamate. It neutralises reactive molecules that damage cells, helps recycle other antioxidants such as vitamins C and E, and supports the liver’s detox pathways. It also matters for mitochondrial health.
Studies from the Baylor research group found that older adults tended to have lower glutathione levels, along with low levels of glycine and cysteine. Their argument is that the shortage comes from a lack of raw materials, not the body’s ability to make it. If that’s right, supplying the missing building blocks should restore production. That’s the theory GlyNAC tests.
The Baylor Trial in More Detail
The 2023 trial compared three groups: older adults on GlyNAC, older adults on placebo (the amino acid alanine), and younger adults who took GlyNAC for two weeks as a reference group. Measurements were taken at the start, at two weeks and at 16 weeks.
| What was measured |
Result in the older GlyNAC group |
| Red blood cell glutathione |
Increased toward young-adult levels |
| Oxidative stress markers |
Decreased |
| Inflammation markers (e.g. IL-6, TNF-α, CRP) |
Decreased |
| Insulin resistance |
Improved |
| Gait speed, muscle strength, 6-minute walk |
Improved |
| Waist circumference, blood pressure |
Improved |
The list is impressive, but the trial had only 24 older adults, all with a BMI over 27, and came from a single lab. Independent replication in larger, more varied groups is the missing piece.
GlyNAC Dose by Body Weight
The trial dose was 100mg per kg of body weight of each ingredient, every day. This table shows what that means in practice, and how it compares with one Aeternum serving (2g + 2g). It isn’t a recommendation to take trial doses. Discuss high doses with your doctor first.
| Body weight |
Trial dose: glycine |
Trial dose: NAC |
Aeternum servings to match |
| 60kg |
6g |
6g |
3 |
| 70kg |
7g |
7g |
3.5 |
| 80kg |
8g |
8g |
4 |
| 90kg |
9g |
9g |
4.5 |
GlyNAC vs NAC Alone vs Liposomal Glutathione
|
GlyNAC |
NAC alone |
Liposomal glutathione |
| What it supplies |
Glycine + cysteine |
Cysteine only |
Glutathione itself |
| Ageing trial evidence |
Small 16-week RCT |
None specific to ageing |
Limited |
| Absorption |
Good (amino acids) |
Good |
Better than plain oral glutathione, but data is limited |
| Typical cost |
Low–moderate |
Low |
Higher |
The Baylor group argues that glycine is also in short supply in older adults, so NAC on its own may not be enough. That’s a reasonable argument, but it hasn’t been tested head-to-head.
Tips for Taking GlyNAC
- Taste: NAC smells and tastes of sulphur. Mix the powder into juice or a smoothie, or wait for capsules.
- Split the dose: taking half in the morning and half in the evening may reduce stomach upset.
- Separate from charcoal and minerals: take NAC at least two hours apart from activated charcoal, zinc or copper supplements.
- Give it time: the positive trial ran for 16 weeks. Judge it over months, not days.
GlyNAC targets a different pathway from NAD+ precursors and Urolithin A, so people sometimes combine them. No trial has tested those combinations. Read our NMN vs NR and Urolithin A guides for the evidence behind each.
Related HealthyPa longevity guides
GlyNAC FAQ
Can I just take glycine and NAC separately?
Yes. GlyNAC is simply the two together, and buying them separately can be cheaper.
Does GlyNAC raise glutathione?
In the 16-week trial in older adults, yes. A larger two-week trial didn’t show an overall effect.
How long does GlyNAC take to work?
The positive trial ran for 16 weeks.
Is GlyNAC the same as taking glutathione?
No. Oral glutathione is poorly absorbed; GlyNAC supplies the building blocks instead.
Does GlyNAC taste bad?
NAC has a strong sulphur smell and taste. Capsules avoid this.
HealthyPa’s Verdict
GlyNAC has one of the more interesting small human trials in the longevity space, and the ingredients are cheap and familiar. But the evidence base is thin, and most supplements, including Aeternum’s, use a much lower dose than the trial. It’s worth considering for older adults who understand those limits.
Medical disclaimer: This article is general information and does not replace medical advice, diagnosis or treatment. Supplements can cause side effects and interact with medicines. Speak with a qualified healthcare professional about your circumstances.
