NAC and Glycine Together: What the Research Can—and Cannot—Tell Us
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What does the research on NAC and glycine actually show?
NAC and glycine are two amino-acid-related compounds the body uses to make glutathione, its main internal antioxidant. A few trials in older adults have tested them together at gram-scale doses with mixed results: one larger trial did not raise glutathione across the whole group, and the studied doses were far higher than the amounts in most daily supplements, including RENEW.
NAC, glycine, and glutathione in plain English
NAC, short for N-acetyl-cysteine, is a compound used in supplements. The body can use it as a source of cysteine, an amino acid needed to make glutathione.
Glycine is also an amino acid and another building block of glutathione. Glutathione is an antioxidant the body makes. Antioxidants help maintain normal defenses against oxidative stress, a form of cell stress that occurs during ordinary metabolism.
Researchers sometimes call the combination of glycine and NAC “GlyNAC.” That shorthand describes the two ingredients together. It does not mean every product with NAC and glycine matches the formula, dose, or setting used in a clinical trial.
The larger trial did not confirm a whole-group benefit
A 2022 randomized dose-finding trial included 114 healthy older adults, whose average age was about 65, along with a younger reference group. The older adults took combined glycine and NAC in a 1:1 ratio at 2.4, 4.8, or 7.2 grams per day for two weeks.
The trial did not meet its primary endpoint: GlyNAC did not raise glutathione measures across the full group. A post-hoc analysis—an analysis selected after the main results were known—found increases only in a subset of participants who began with both high oxidative stress and low glutathione and took the medium or high dose. The researchers reported that the tested doses were safe and well tolerated during the study.
These findings came from 2.4 to 7.2 grams per day of combined GlyNAC. RENEW provides 225 mg of NAC and 200 mg of glycine per serving, or about 0.425 gram combined. The trial doses were many times larger, so even the subset finding cannot be treated as a result that RENEW will produce.
A small 16-week trial was encouraging, but limited
A 2022 randomized controlled trial studied only 24 older adults: 12 received GlyNAC and 12 received a placebo, with a younger group included for reference. Each participant in the treatment group received 100 mg per kilogram of body weight per day of glycine and the same amount of NAC for 16 weeks. For an adult weighing about 70 kilograms, that works out to roughly 7 grams of each ingredient, or about 14 grams combined each day.
The researchers reported improvements in glutathione, measures related to mitochondria—the structures within cells that help produce energy—and some measures of physical function. Those results occurred at roughly 14 grams per day for a typical adult, not at RENEW's 0.425 gram combined serving, so they cannot be transferred to RENEW.
The authors also described important limits. The trial was small and enrolled healthier older adults to focus on aging itself. They said larger studies in more typical older adults were needed. The reported gains were lost after supplementation stopped. Again, those observations belong to a 16-week trial using about 14 grams per day for a 70-kilogram adult—many times the amount in RENEW—not to RENEW or to every NAC and glycine supplement.
Taken together, the research is encouraging in places but small and unsettled overall. The larger dose-finding trial did not find its intended whole-group result, while the positive 16-week trial included only 24 older adults.
The dose reality matters
Milligrams and grams can look deceptively similar on a label. One gram equals 1,000 milligrams. RENEW contains 225 mg of NAC plus 200 mg of glycine per serving: 425 mg, or about 0.425 gram, combined.
By comparison, the dose-finding trial used 2.4, 4.8, or 7.2 grams combined each day. The 16-week trial used 100 mg per kilogram per day of each ingredient, which is roughly 14 grams combined for a 70-kilogram adult. Both trials therefore tested amounts many times larger than RENEW's amounts. RENEW is not the studied dose.
Dose is only one difference. Study length, participant selection, and what researchers measured also shape what a trial can tell us. A supplement label and a study abstract should be compared ingredient by ingredient and amount by amount.
How this relates to RENEW — and how it doesn't
RENEW includes NAC and glycine as part of a broader formula that supports the body's normal antioxidant defenses. You can see the disclosed amount of every ingredient on the RENEW ingredients page.
RENEW provides 225 mg of NAC and 200 mg of glycine per serving. Those amounts are far below the gram-scale doses used in both trials: 2.4–7.2 grams combined per day in the dose-finding study and roughly 14 grams combined per day for a typical adult in the 16-week study. The trial results cannot be transferred to RENEW, and no particular outcome or timeframe is promised.
RENEW also pairs these ingredients with vitamin D3. See our guide to how much vitamin D3 older adults need for the dose questions worth asking.
Questions to ask your doctor or pharmacist
Your health history, medicines, and other supplements can affect whether a product fits your situation. Consider taking the full label to your doctor or pharmacist and asking:
- Could NAC, glycine, or another ingredient interact with any medicine or supplement I use?
- Are 225 mg of NAC and 200 mg of glycine appropriate for my situation?
- Does any health condition change whether I should use this product?
- Is there anything you would want to monitor if I take it?
- How should I compare this serving with other products that also contain NAC or glycine?
These questions support an informed conversation. They are not a substitute for individual medical advice.
Written by The Novera Team. Last reviewed: 2026-07-19.
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.