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Supplements

GlyNAC

A glycine and N-acetylcysteine combination with promising but preliminary human data on glutathione and aging-related markers.

Emerging
Evidence rating
Evidence review

What the evidence says

GlyNAC combines glycine and N-acetylcysteine, two inputs used to make glutathione. The main longevity interest comes from a 16-week placebo-controlled trial in 24 older adults that reported changes in glutathione status, oxidative-stress markers, mitochondrial measures, inflammation, and several physical-function outcomes.[1]

A separate dose-ranging trial enrolled 114 healthy older adults for two weeks. It found that GlyNAC was well tolerated and suggested that some participants with higher oxidative stress and lower baseline glutathione might respond, but the brief duration and subgroup findings do not establish durable clinical benefit.[2]

Earlier evidence is weaker: a small open-label pilot in older adults and an eight-person open-label study in people with HIV reported broad biomarker and functional changes, but neither design can separate treatment effects from time, expectation, or regression to the mean.[3][4]

A 2026 review describes the program as proof of concept, but the core interventional studies come from the same research group and use biomarkers or exploratory outcomes. GlyNAC remains plausible and testable, not proven as a healthy-aging intervention; larger independent trials need clinically meaningful outcomes and longer follow-up.[1][2][5]

Potential benefits

  • May raise glutathione availability in older adults with higher oxidative stress or lower baseline status.[2]
  • A small controlled trial reported improvements across exploratory metabolic and physical-function measures.[1]

Side effects and cautions

  • The cited short trials described GlyNAC as safe and well tolerated.[1][2]
  • Long-term safety, ideal dosing, and interactions remain insufficiently characterized for a healthy-aging indication.[1][2]
How we scored it

Evidence breakdown

Small, short trials report biomarker and functional changes, but replication and clinically meaningful long-term outcomes are missing.

Clinical relevanceLow

Most reported outcomes are biomarkers or exploratory physical-function measures.

Study qualityLow

Key findings come from small samples and short interventions without broad replication.

Safety dataModerate

Short trials report good tolerability, but long-term combination data are limited.

References

Full source list

  1. Supplementing Glycine and N-Acetylcysteine in Older Adults Improves Glutathione Deficiency and Multiple Aging Hallmarks: A Randomized Clinical Trial

    The Journals of Gerontology: Series A · 2023

  2. 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

  3. Glycine and N-acetylcysteine supplementation in older adults improves glutathione deficiency and multiple aging-related measures: Results of a pilot clinical trial

    Clinical and Translational Medicine · 2021

  4. Supplementing Glycine and N-acetylcysteine in Aging HIV Patients: Results of an Open-Label Clinical Trial

    Biomedicines · 2020

  5. Glycine and N-acetylcysteine supplementation, with or without exercise, in brain health and functional aging

    Frontiers in Nutrition · 2026