Glycine (high-dose) — The Sleep and Autophagy Amino Acid
Glycine is a non-essential amino acid that functions as an inhibitory neurotransmitter and a fundamental building block for collagen and glutathione. In longevity medicine, high-dose glycine is primarily utilized to improve sleep architecture, lower core body temperature, and support cellular detoxification and autophagy.
Mechanism of Action
Glycine acts as an inhibitory neurotransmitter in the central nervous system, binding to glycine receptors in the brainstem and spinal cord to promote relaxation and lower core body temperature, which facilitates sleep onset. Systemically, it is a crucial component of collagen and a rate-limiting precursor for the synthesis of glutathione, the body's primary endogenous antioxidant. In longevity models, glycine supplementation has been shown to extend lifespan by mimicking the metabolic effects of methionine restriction, activating autophagy, and reducing oxidative stress. It also modulates NMDA receptors, influencing cognitive function and neuroplasticity.
Human Trial Evidence
Multiple small randomized controlled trials have demonstrated that 3 grams of glycine before bed improves subjective sleep quality, reduces sleep onset latency, and enhances daytime cognitive performance in sleep-restricted individuals. A 2012 trial in Neuropsychopharmacology and earlier studies in Sleep and Biological Rhythms (2007) confirm these effects. In the context of aging, human trials combining glycine with N-acetylcysteine (GlyNAC) show improvements in glutathione levels, mitochondrial function, and physical strength in older adults, though isolated high-dose glycine longevity trials in humans are lacking.
Dosing Protocol
3 grams (3,000 mg) taken 1–2 hours before bedtime is the most studied dose for sleep enhancement in human trials. It is typically administered as a powder dissolved in water. For general longevity and metabolic support, some protocols use 3–5 grams daily. High-dose protocols (up to 15–60 grams daily) have been used in psychiatric research (e.g., schizophrenia) but are not standard for longevity.
Safety & Contraindications
Glycine is generally recognized as safe and well-tolerated at standard doses of 3–5 grams daily. Mild gastrointestinal distress (nausea, upset stomach) may occur at higher doses. High-dose glycine (e.g., >15 grams) is contraindicated in patients taking clozapine, as it may reduce the drug's antipsychotic efficacy. Caution is advised for individuals with severe kidney or liver impairment due to the nitrogen load.
Key Papers
Glycine ingestion improves subjective sleep quality in human volunteers, correlating with polysomnographic changes
Sleep and Biological Rhythms · 2007
The effects of glycine on subjective daytime performance in partially sleep-restricted healthy volunteers
Frontiers in Neurology · 2012
Glycine and aging: Evidence and mechanisms
Ageing Research Reviews · 2023