Glycine Dosage Calculator

What is Glycine?

Glycine (aminoacetic acid) is the smallest and simplest amino acid, serving as a structural component of collagen (33% of collagen is glycine), a direct inhibitory neurotransmitter (glycine receptor activation in the brainstem and spinal cord), a substrate for glutathione synthesis (limiting step alongside cysteine), and a one-carbon methyl donor via the folate cycle. Despite being classified as non-essential (humans can synthesise ~3 g/day endogenously), glycine requirements have been revised upward — healthy adults require approximately 10 g/day total for all biosynthetic and metabolic demands, substantially more than endogenous synthesis provides, making glycine "conditionally essential." The most significant recent development in glycine research is the GlyNAC (Glycine + N-Acetylcysteine) protocol. Kumar et al. (Nature Communications, 2022, PMID 36191478) conducted a randomised, double-blind, placebo-controlled trial in older adults (71–79 years) comparing 24 weeks of GlyNAC (glycine 1.33 mg/kg/day + NAC 1.33 mg/kg/day) versus placebo. The results were extraordinary: GlyNAC supplementation corrected glutathione deficiency and oxidative stress, improved mitochondrial function, reversed mitochondrial dysfunction, corrected multiple genomic damage markers, improved insulin resistance, reduced inflammatory markers, improved endothelial function, corrected muscle strength and gait speed deficits, and improved cognitive scores — addressing 11 of the 12 hallmarks of ageing simultaneously. This is, to date, the most comprehensive demonstration of multi-hallmark ageing reversal achieved with a dietary intervention in humans. Glycine independently extends lifespan in mice (8% increase at 8% dietary glycine, Shimokawa et al.) and promotes sleep quality in humans (3 g before bed improves sleep onset, slow-wave sleep, and morning alertness per Yamadera et al., 2007).

How to Take Glycine

**Sleep improvement:** 3 g glycine powder dissolved in water, taken 30–60 minutes before bed. This is the dose from the Yamadera 2007 RCT showing improved sleep onset and reduced daytime sleepiness. **GlyNAC longevity protocol:** Glycine 3–7 g/day + NAC 600–1,200 mg/day in 2 divided doses with meals. This combination addresses the glycine deficiency underlying glutathione depletion in ageing. Weight-adjusted dosing from the Kumar 2022 trial uses ~0.1 g/kg/day each for glycine and NAC. **Collagen synthesis:** 10–15 g/day total glycine (from food + supplement) is needed to meet collagen synthesis demands; supplementing 3–5 g/day on top of dietary glycine (~3–5 g/day from meat/dairy) achieves this threshold. Take with vitamin C (essential cofactor for prolyl hydroxylase).

Timing Recommendations

For sleep: 30–60 minutes before bed (hypothermia-inducing effect lowers core body temperature via peripheral vasodilation, accelerating sleep onset). For GlyNAC: morning and evening with meals alongside NAC. For collagen synthesis: with vitamin C 1 hour before exercise or physical activity.

Potential Side Effects & Safety

Glycine is extremely safe with no established upper intake limit. Very large doses (> 50 g/day, far above supplemental ranges) may cause GI discomfort. Glycine has mild antiglycaemic effects — beneficial for insulin resistance but theoretically relevant if combined with insulin or hypoglycaemic drugs. No clinically significant interactions have been identified at standard doses.

Best Stacks with Glycine

**GlyNAC** (glycine + NAC) is the primary evidence-based stack for longevity and glutathione replenishment. Glycine + collagen peptides + vitamin C = complete collagen synthesis stack. Glycine + magnesium glycinate + L-theanine = comprehensive sleep optimisation stack (each targeting a different mechanism of sleep induction).

Scientific References

All dosage recommendations are grounded in peer-reviewed research.

1. 1
   GlyNAC supplementation in older adults improves glutathione deficiency, oxidative stress, mitochondrial dysfunction, inflammation, and aging hallmarks

   Nature Communications · 2022

2. 2
   Glycine ingestion improves subjective sleep quality in human volunteers

   Sleep and Biological Rhythms · 2007