Supplement · graded by use, two uses
GlyNAC (Glycine + N-Acetylcysteine)
Glutathione, oxidative stress and aging markers in older adults (originating group's trial).
Grade C: human trials exist, but they are small, mixed or not yet repeated. This is not a finding that it does not work. How to read a grade →
GlyNAC is glycine plus NAC, two building blocks the body uses to make a natural protective substance. The research group that first studied it reported better blood tests and signs of aging in older adults. But the one study run by an outside group found no change in healthy older adults. That outside study was paid for by a company that sells glycine.
The C belongs to one of the two uses graded on this record. The other one carries its own letter.
As studied, and the trials
This is the only trial of GlyNAC not run by the originating group and it missed its primary endpoint The one outcome a trial names in advance as its main test. Results on other outcomes carry less weight. in healthy older adults; it was sponsored by the product's commercial owner and used a lower dose for a shorter time.
As studied, and the trials
Kumar and Sekhar's one randomized placebo-controlled trial, in 24 older adults for 16 weeks (PMID PubMed ID: the permanent number the US National Library of Medicine gives a published paper. Each one links to that paper's record on PubMed. 35975308), reports benefit on glutathione and downstream aging markers; the 2021 older-adult study (PMID 33783984) and the group's HIV and type 2 diabetes studies are open-label Everyone in the trial knows which treatment they are receiving, so expectations can shape the results, especially for symptoms people report themselves. pilots. The trial randomized older adults, not people selected for high oxidative stress or low glutathione; the 'elevated demand' subgroup comes from the sponsor trial's post hoc analysis, not from how anyone was enrolled. The entire positive evidence base originates from a single investigator group at Baylor. The one trial by another group, in HEALTHY older adults at a lower dose for 2 weeks, was null on its primary endpoint The outcome a trial measures to decide whether the treatment worked, such as heart attacks, blood pressure or a symptom score. but found a signal post hoc in the subset with high oxidative stress and low baseline glutathione. The two results are compatible. That is why this use holds at C rather than dropping to D: the other trial did not contradict the effect at the originating group's dose and duration, which it did not test.
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A letter describes the human evidence, not the product, the manufacturer, or the ingredient's worth.
See the full evidence record →Funding: The single trial this Grade D for Glutathione redox status in healthy older adults rests on was funded by the maker of the product it tested. The funder's role in design and analysis is not stated here, because the full trial report could not be read. The letter is what the trial supports under the grading rules; the funding is stated here so it can be weighed alongside it. Investigators: The single trial this Grade D for Glutathione redox status in healthy older adults rests on was run by investigators employed by, founded by, or belonging to the organization that developed, sells or teaches the intervention (employees of the sponsor and its research institute). The funder may read non-commercial; the people who ran the trial are part of the organization whose intervention they tested, which is stated here so it can be weighed alongside the letter.
Glutathione and oxidative stress markers in older adults: positive in the originating group's trial, null in the one independent trial.
How this letter has changed · latest: October 2026 · Corrected
The healthy-older-adults use called Lizzo 2022 (PMID 35821844) an independent trial; its paper discloses that the sponsor holds and licenses patents on glycine plus N-acetylcysteine and markets the products, so it is a maker-funded null, which strengthens rather than weakens it, and its 2.4 to 7.2 g/day for 2 weeks is now set against the originating group's roughly 14 g/day for 16 weeks. The other use said 'randomized trials' in the plural; only Kumar 2023 (PMID 35975308) is randomized and placebo-controlled, the 2021 study (PMID 33783984) is an open-label pilot, and the note now says so. The 'populations with elevated demand' label described a post hoc subgroup from the sponsor trial rather than how Kumar 2023 enrolled people, so the use and title now name older adults. The unverifiable 'BMI above 27' entry criterion is removed. The 'sponsored' flag is replaced by a funding_basis block naming who sponsored which trial. Letters unchanged; the D versus C question on the healthy older adults use is on the decision sheet.PMID 35821844 PMID 35975308 PMID 33783984
Every change to a letter on this site is dated and published. The full evidence log →
Commercial disclosure
EBL earns no commission on any supplement it grades. A purchase made through the dispensary link below pays EBL nothing, the practitioner discount goes to you in full. The dispensary is Fullscript, a practitioner dispensary, and many of the professional-grade brands in it are sold mainly through practitioners rather than in health food stores. Grades are assigned by published rubric before any commercial relationship exists and are never influenced by one. Full disclosure.
Sekhar trials dosed glycine and NAC each at ~100 mg/kg/day (about 7 g of each per day for a 70 kg adult), split into two daily doses. Commercial GlyNAC products are often far lower than the Sekhar trial protocols.
GlyNAC can be delivered as glycine plus N-acetylcysteine, but match the doses to the regimen used in the supporting trial. A commercial combined capsule or a separate-product regimen is not equivalent to the trial simply because both substrates are present.
In the cited 14-day trial in healthy older adults, each day's amount was split into a morning and an evening dose (PMID 35821844). The other cited trial reports do not state a time (PMID 35975308, PMID 33783984).
Checked against the full report for 2 of the 3 cited studies, and the published summary for the rest. What the cited trials did, not a schedule. Every supplement, by trial timing →
How to buy this: quality criteria, not a brand
Weight-based per the Sekhar protocol. The trial effect depends on both the glycine and the NAC dose.
The glycine+NAC combination is what was studied; single-component data differs.
Both component doses printed; third-party tested.
Products that don’t state both doses; assuming glycine-alone or NAC-alone equals the combo.
The grade and these criteria are set only from human trials. Any purchase link is convenience and does not affect the grade.
Asthma, on the NAC component and its bronchospasm risk. Pregnancy. The glycine component carries the clozapine caution described on the glycine entry, which is easy to miss in a combination product.
Everything on the NAC entry and everything on the glycine entry applies here, which is the honest headline for any combination product: nitroglycerin potentiation, antiplatelet activity, the chemotherapy question, and clozapine. No interaction study has been done on the combination itself.
Mechanism-based, no human interaction study located. The drug interactions described for GlyNAC (Glycine + N-Acetylcysteine) are mechanism-based. A PubMed search for human interaction, pharmacokinetic or co-administration studies pairing it with antiplatelet, chemotherapy, clozapine returned no results in August 2026. The caution stands on pharmacology, not on a trial, and is labeled as such. Basis: pharmacological mechanism, not a human study. Searched PubMed in August 2026: 3 queries, 0 human results.
The trials measured clinical outcomes relevant to the indication, including grip strength, walking performance and glycemic measures.
Primary evidenceThree papers, each linked to its PubMed record.
Kumar, Sekhar et al. (J Gerontol A Biol Sci Med Sci, 2023; PMID 35975308): 24 older adults randomized to GlyNAC or isonitrogenous alanine placebo An inactive substitute made to look like the real treatment, so participants cannot tell which one they received. for 16 weeks, NIH-funded; GlyNAC and not placebo corrected glutathione deficiency in red blood cells, lowered oxidative stress, improved mitochondrial fuel oxidation, lowered insulin resistance and inflammation, improved endothelial markers and systolic blood pressure, and increased gait speed and grip strength. The abstract does not state a BMI entry criterion. The Grade C rests on this trial. Kumar et al. (Clin Transl Med, 2021; PMID 33783984) is a 24-week open-label pilot in 8 older adults with no placebo group; supporting context that does not carry the grade. Lizzo et al. (Front Aging, 2022; PMID 35821844): randomized controlled trial People are assigned to the treatment or a comparison by chance, so the groups differ only in what they received. It is the design that can show cause and effect., 114 healthy older adults, 2.4, 4.8 or 7.2 g/day total for 2 weeks; no change in the reduced-to-oxidized glutathione ratio or total glutathione, the primary endpoint; run and sponsored by a company that holds and licenses patents on glycine plus N-acetylcysteine and markets the products, so the null result came from the product's commercial owner. Its dose (2.4 to 7.2 g/day) and duration (2 weeks) are far below the originating group's protocol of about 100 mg/kg/day of each amino acid, roughly 14 g/day total, for 16 weeks.
Every positive GlyNAC trial to date comes from one research group (Sekhar, Baylor College of Medicine). The only independent randomized trial (Lizzo et al., Front Aging 2022; PMID 35821844, n=114 healthy older adults) did not meet its primary endpoint of raising total glutathione. It tested roughly half the dose for one eighth the duration in a population without baseline glutathione deficiency, so it does not refute the studied protocol, but no independent replication of that protocol exists. The aging hallmark findings in PMID 35975308 were added as exploratory outcomes after trial completion and rest on Western blots from 3 participants per group; they do not carry the grade.
Educational use only · Not medical advice · Starting, stopping or changing any supplement or medication is a decision for your physician
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. The grade on this page describes the strength of published human trial evidence in the populations studied. It is not a recommendation for any individual and is not medical advice. Starting, stopping or changing any supplement or medication is a decision for your physician.
Trials report an average. This box says whether any trial on this record looked at who the result applies to, and what it found.
For Glutathione, oxidative stress and aging markers in older adults (originating group's trial), Grade C · Subgroup tested, effect differedThe trials randomized older adults, not people selected for high oxidative stress or low glutathione. The 'elevated demand' subgroup comes from an analysis of the originating group's trial (PMID 35975308) done after the results were in, and the trial by another group in healthy older adults (PMID 35821844) found a signal only in the same kind of after-the-fact analysis, in people with high oxidative stress and low baseline glutathione. A subgroup result shows who the effect appeared in within these trials. It does not change the letter. This subgroup was identified after the results were in and has not been confirmed in a trial designed to test it.
This page carries a letter. EBL takes no commission, referral fee or payment of any kind on anything it grades. No letter has been bought and none is for sale.
How this is enforced
That is not a promise, it is a build condition. Two checks run on every deploy: one refuses to publish if a commission is claimed on anything graded, the other refuses if a page names a commercial relationship that is not declared in the register. If either fails, this page does not go live. You can read how the checks work, and what they do not cover, on the evidence integrity page.
How EBL searched for the trials (1 search)
The search that was run, what it returned, and what was left out and why, so the absence of evidence can be checked as well as its presence.
("glycine and N-acetylcysteine"[tiab] OR GlyNAC[tiab]) AND humans[mesh]Grades move when new trials publish. A free monthly email lists every grade EBL moved, with the reason and the trial behind it: the sign-up is on the Evidence Log →