Glycine
Simple amino acid supporting collagen, sleep, glutathione synthesis, and methionine balance.
Evidence Summary
Glycine is best supported when paired with N-acetylcysteine as "GlyNAC," a combination that replenishes the body's master antioxidant, glutathione. In a 16-week randomized, placebo-controlled trial in older adults (The Journals of Gerontology: Series A, 2023; 100 mg/kg/day each of glycine and NAC), GlyNAC raised red-blood-cell glutathione by about 225% and muscle glutathione by about 164%, lowered oxidative-stress markers (plasma TBARS and F2-isoprostanes) by about 72%, and reduced inflammatory markers (interleukin-6 by ~78%, TNF-alpha by ~54%, hs-CRP by ~41%) versus placebo, with parallel improvements reported in mitochondrial function, insulin sensitivity, gait speed, muscle strength and cognition. A 2024 pilot clinical trial extended these findings toward brain aging, reporting improved cognition, mitochondrial function and BDNF after 24 weeks. Glycine on its own supports sleep quality and, in a small 2025 exploratory study in people with severe obesity (2 weeks, 100 mg/kg/day), lowered triglycerides and liver enzymes (ALT/AST), though glutathione, glucose and weight were unchanged over that short window. Glycine remains simple, inexpensive and well tolerated. Benefits are most pronounced when glutathione is depleted; these are mostly small, short trials, and glycine/GlyNAC is an adjunct to, not a replacement for, medical care. Educational information, not medical advice.
Evidence Scale
Mechanism of Action
Glycine is an inhibitory neurotransmitter, a collagen building block, and one of the three amino acids used to synthesize glutathione, the body's principal intracellular antioxidant. Combined with N-acetylcysteine (which supplies cysteine, the rate-limiting glutathione precursor), glycine helps restore glutathione synthesis that declines with age — improving redox balance, mitochondrial fuel oxidation and inflammatory tone. Glycine may also partly mimic methionine-restriction signaling relevant to longevity.
Who Is This For?
Sleep improvement, collagen support, glutathione production, longevity (methionine balance).
Protocol & Dosing
Dose
3-5g before bed for sleep. 10-15g daily for collagen/longevity benefits.
Frequency
Daily
Duration
Ongoing
Protocol Summary
Oral powder. For sleep, 3 g dissolved in water before bed; higher intakes (10-15 g/day) are used for collagen and longevity support. For the glutathione (GlyNAC) protocol, glycine is combined with N-acetylcysteine and dosed by body weight under clinician supervision, with biomarker monitoring. Introduce gradually to limit any GI upset.
Latest Evidence
2023–2025: GlyNAC restores glutathione, plus brain-aging & metabolic signals
Glycine's strongest longevity evidence comes when it is paired with N-acetylcysteine as “GlyNAC.” In a 16-week randomized, placebo-controlled trial in older adults (100 mg/kg/day of each), GlyNAC raised red-blood-cell glutathione by roughly 225% and muscle glutathione by about 164%, cut oxidative-stress markers (plasma TBARS and F2-isoprostanes) by about 72%, and lowered inflammatory markers (IL-6 ~78%, TNF-α ~54%, hs-CRP ~41%) versus placebo — with parallel improvements reported in mitochondrial function, insulin sensitivity, gait speed, muscle strength and cognition. A 2024 pilot trial extended these findings toward brain aging, reporting improved cognition, mitochondrial function and BDNF. Glycine on its own supports sleep quality, and a small 2025 exploratory study in severe obesity found lower triglycerides and liver enzymes after two weeks, while glutathione, glucose and weight were unchanged over that short window.
These are mostly small, short trials, and combination effects (GlyNAC) cannot be attributed to glycine alone. Glycine and GlyNAC are adjuncts, not substitutes for medical care; benefit is greatest when glutathione is depleted. Introduce gradually to limit GI upset and use under qualified clinician supervision with biomarker monitoring. Educational information, not medical advice.
Randomized placebo-controlled trial · 16 weeks · 2023
GlyNAC vs placebo: glutathione up, oxidative stress & inflammation down
Mean change vs placebo after 16 weeks of GlyNAC (glycine + N-acetylcysteine, 100 mg/kg/day each) in older adults. Source: Kumar et al., The Journals of Gerontology: Series A (2023).
Related on Peak Human
Glycine (Supplement)
The paired supplement monograph: forms, dosing and quality.
NAC (N-Acetyl Cysteine)
Glycine’s partner in GlyNAC for glutathione synthesis.
Sleep
Glycine (~3 g at night) supports sleep quality and onset.
Longevity
Glutathione restoration is a core healthy-aging lever.
Diagnostic Testing
Track glutathione status, oxidative stress and inflammation.
Peak Human Shop
Practitioner-grade glycine and glutathione support.
Key references: GlyNAC in older adults: randomized clinical trial — J. Gerontol. A Biol. Sci. Med. Sci. (2023) · GlyNAC, glutathione, mitochondria & cognition: pilot trial in aging — Innovation in Aging (2024) · Dietary glycine supplementation in severe obesity — Scientific Reports (2025)
Interactions & Precautions
Contraindications
- None established
Potential Risks
- •None significant
Potential Side Effects
Practitioner Notes
Clinical annotations from Dr. Goel
Simple, cheap and well tolerated. For glutathione restoration, pair glycine with NAC (the GlyNAC combination used in trials was ~100 mg/kg/day of each) and monitor inflammatory and oxidative-stress markers. For sleep, 3 g at night is often sufficient. Sweet taste makes compliance easy.
Dr. Sanjeev Goel
Chief Medical Officer, Peak Human
Cost & Access
Cost Range
$
Accessibility
Availability varies by location
Sample member
Longevity Operator
One number for your longevity journey.
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- Metabolic
- Hormonal
- Cardiovascular
- Brain / Cognitive
- Sleep
- Musculoskeletal
- Gut
- Immunity / Inflammation