GlyNAC is an inexpensive daily pairing of glycine and N-acetylcysteine that supplies the building blocks for glutathione, the body's main internal antioxidant. Early, mostly single-group human studies link it to lower oxidative stress, better strength and thinking, but benefits fade after stopping and appear mainly in those starting out deficient. Promising but unproven. (Full Review)

Protocol

Standard Dose

~100 mg/kg/day each

Glycine + NAC, 1:1 ratio (~7 g + 7 g for a 70 kg adult)

Lower Alternative

2.4–7.2 g/day total

Fixed-dose 1:1 glycine:NAC; effect seen at medium and high doses

Schedule

Split into 2 doses

Take with food; start low and escalate over 1–2 weeks

Time to effect

Glutathione & Oxidative Stress

~2 weeks

Markers can shift within a couple of weeks

Strength & Gait Speed

Months

Functional gains assessed over months of continued use

Overall Trial Window

2–24 weeks

Range over which biomarker and functional changes were measured

Benefits

Medium: Restored glutathione & reduced oxidative stress; improved mitochondrial fuel oxidation & insulin sensitivity

Low: Muscle strength, gait speed & physical function; reduced inflammation & improved endothelial function; cognitive function

Speculative: Lifespan extension; slowed aging-hallmark progression

Contraindications

Pregnancy or breastfeeding (insufficient safety data)

Active asthma or history of bronchospasm with NAC

History of cysteine-related kidney stones

Nitrates or anticoagulants without medical supervision

Severe kidney impairment

Key Interactions

Nitroglycerin and other nitrates

Antiplatelet and anticoagulant drugs (aspirin, clopidogrel, warfarin, apixaban)

Activated charcoal

Other antioxidant supplements (high-dose vitamin C, vitamin E, alpha-lipoic acid, standalone NAC or glutathione)

Blood-pressure-lowering supplements and drugs (beetroot/nitrate products, magnesium, potassium)

Risk & Side Effects

Low: Gastrointestinal upset; theoretical reduction of exercise-training adaptations

Speculative: Sex-specific adverse response; excess antioxidant / reductive stress; pulmonary hypertension signal with NAC

Monitoring

Marker	Target	Why
Glutathione (GSH), RBC or whole-blood	Trend upward toward young-adult levels	Direct target of GlyNAC
hs-CRP	< 1.0 mg/L	General marker of systemic inflammation, expected to fall if effective
Fasting glucose	70–90 mg/dL	Tracks metabolic effect and insulin-sensitivity claims
Fasting insulin	2–6 µIU/mL	Reflects insulin resistance, a reported GlyNAC target
HbA1c	< 5.4%	Longer-term metabolic control
MDA	Lower within assay reference	Direct oxidative-damage readout used in GlyNAC trials
eGFR	> 60 mL/min/1.73m²	Safety check given high amino-acid load

Cadence: Baseline before starting, then at ~8–12 weeks, and every 6–12 months for long-term use

Qualitative Assessment

Energy levels and exercise tolerance through the day
Muscle strength and grip in daily tasks
Walking speed and physical endurance
Cognitive clarity, focus, and memory
Sleep quality, especially if glycine is taken in the evening
General sense of recovery after exertion

GlyNAC for Health & Longevity

Protocol

Benefits

Risk & Side Effects

Monitoring

Qualitative Assessment