Supplement analysis backed by scientific evidence · PT

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Limited evidenceLongevity & antioxidants

GlyNAC

GlyNAC — glycine plus N-acetylcysteine — restores glutathione in older adults, which is not in dispute. What is in dispute is whether that translates into better function: one research group reports broad improvements, while an independent, larger trial found restored glutathione and little else.

What the science says

  • Reliably corrects glutathione deficiency in older adults Moderate evidence

    Both the Baylor trials and an independent randomized controlled trial in healthy older adults found that supplying the two rate-limiting glutathione precursors restores red blood cell glutathione toward young-adult levels within 2-16 weeks. This is the most consistently replicated GlyNAC finding across laboratories.

  • Broad functional benefits reported by a single group Limited evidence

    In a randomized clinical trial of 24 older adults taking glycine and NAC at roughly 100 mg/kg/day each for 16 weeks, the investigators reported improvements in oxidative stress, mitochondrial fuel oxidation, inflammation, insulin resistance, endothelial function, gait speed, muscle strength, cognition, blood pressure and waist circumference. The sample was very small and single-centre, and effectively all positive GlyNAC outcome data come from one research team — an unusual concentration of evidence for such wide-ranging claims.

  • An independent trial did not reproduce the functional effects Moderate evidence

    A separate randomized controlled trial in healthy older adults found that glycine and NAC supplementation restored glutathione redox status but did not significantly reduce markers of oxidative damage or improve the functional outcomes assessed. This is the single most important fact about GlyNAC and it is rarely mentioned in marketing: biomarker correction happened, downstream benefit did not.

  • Consumer products are dosed far below the trials Limited evidence

    The studied dose is weight-based — about 100 mg/kg/day of each compound, meaning roughly 7 g glycine plus 7 g NAC daily for a 70 kg adult. Typical retail GlyNAC capsules supply 1-2 g total per day, a fifth or less of the trial dose, and there is no evidence that a fractional dose produces any of the reported effects.

Dosage & safety

Studied doseTrials used glycine 1.33 mmol/kg/day and NAC 0.81 mmol/kg/day, approximately 100 mg/kg/day of each, for 16 weeks — about 6-8 g of glycine and 6-8 g of NAC daily for a 70 kg adult, split across meals. That is a powder dose, not a capsule dose. Glycine is sweet and mixes easily; NAC is sulfurous and best taken with food to limit nausea. There is no established maintenance dose and no long-term safety data beyond roughly 16-24 weeks at these amounts.
SafetyNAC commonly causes nausea, vomiting, diarrhea and a sulfur taste, especially at multi-gram doses; rare hypersensitivity and bronchospasm occur. NAC has vasodilatory and antiplatelet properties — caution with nitroglycerin (severe hypotension and headache) and with anticoagulants or antiplatelets. Regulatory status is unsettled: the FDA has asserted NAC was approved as a drug before being marketed as a supplement and currently exercises enforcement discretion for supplement sales, but that can change and availability differs by country. Glycine at multi-gram doses can cause GI upset and mild sedation and should be used cautiously with clozapine, whose effect it may reduce. Neither compound is banned in sport. Avoid in pregnancy and breastfeeding without medical advice, and discuss with a clinician if you have asthma, kidney disease or take nitrates. Treat GlyNAC as an interesting hypothesis still under test, not an established anti-aging intervention.

Scientific references

Where to buy

Nutri, Glynac-ET, 60 Vegan Capsules

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