Glycine
Amino acid that supports glutathione production with NAC and may deepen slow-wave sleep.
Summary
Debbie covers glycine in two roles: as a limiting building block (with cysteine) for glutathione, which declines with age, and as a bedtime supplement that may improve sleep quality and slow-wave sleep. Human studies she cites used 3 g before bed for sleep and glycine plus NAC for glutathione, cognition and physical function in older adults. She points to collagen, gelatin and bone broth as dietary sources.
Prefers glycine powder over capsules to avoid unneeded cellulose capsules and because it is cheaper per serving.From Glycine for Improving Slow-Wave Deep Sleep
The evidence
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Human trial
In a 6-month clinical trial in adults aged 70+, glycine plus NAC corrected glutathione deficiency and improved inflammation, insulin resistance, cognition, strength, walking speed and exercise capacity.
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Human trial
In elderly adults, glycine plus cysteine raised glutathione by 94.6% within two weeks, back in line with younger people.
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Human trial
In a human study, 3 g of glycine before bed improved sleep quality, sleep efficacy and how quickly participants reached slow-wave sleep.
Read the study Discussed in Glycine for Improving Slow-Wave Deep Sleep -
Human trial
In sleep-restricted human participants, 3 g of glycine significantly reduced next-day fatigue without affecting melatonin or core clock genes.
Read the study Discussed in Glycine for Improving Slow-Wave Deep Sleep -
Animal
In very old mice, glycine plus NAC reversed cognitive decline.
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Animal
In old mice, glycine plus cysteine improved heart function and lowered inflammatory markers.
Doses used in studies
Amounts reported in the research, not dosing recommendations.
| Dose | Context |
|---|---|
| 3 g before bed | Human sleep-quality and sleep-restriction studies |
| 1.33 mmol/kg/day (about 6 g/day for a 130 lb person, split into two doses) | Glycine + NAC studies in older adults |
| Up to 0.8 g/kg/day (split into 2-4 doses) or 15-30 g/day | Clinical trials in patients with schizophrenia, cited for safety at higher amounts |
Cautions
- Because glycine also acts with glutamate as an excitatory co-agonist, there is a limit to how much to take; sleep benefits are likely in the 3-5 g range.
- Glycine may inhibit wound healing by slowing blood vessel growth (which might also slow tumor growth).
- In rats the LD50 is 7,930 mg/kg: fairly safe, but there is a maximum dose.