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Amino acid

Glycine

Glycine is the simplest amino acid. The body can make it itself, and it is abundant in collagen and other protein-rich foods.

Also listed as 2-Aminoacetic acid, L-Glycine

SleepLongevityOrgan FunctionCognitionCardiovascular

Could glycine help with sleep?

A systematic review found small studies using 3 g before bed for only a few nights. Some sleep measures improved, but small samples and high risk of bias limit confidence. The promising question is whether these early benefits persist in larger, longer trials. 1

Sleep qualityToo little evidence

Short studies suggest benefit; dependable estimates of the size and durability of improvement are still lacking. 1

What happened after a shortened night?

In a crossover experiment, seven healthy men completed testing after restricting sleep by 25%. They received 3 g of glycine or placebo before bed for three nights. Fatigue improved on day one but not day three; vigilance-test performance improved on both tested days. Several authors worked for the manufacturer Ajinomoto. 2

Mental EnergyToo little evidence

An early finding under experimental sleep restriction, not evidence that glycine replaces adequate sleep. 2

Does it improve concentration?

A small crossover trial in young and middle-aged adults found better retrieval of episodic memories. Focused and divided attention did not improve; sustained attention improved only in the middle-aged group. These different results deserve more precision than a general claim of sharper thinking. 3

MemoryToo little evidence

An encouraging memory-test result from a small trial needs replication. 3

Why is GlyNAC being studied in aging?

A 16-week randomized trial enrolled 24 older adults and tested glycine plus N-acetylcysteine, called GlyNAC. Oxidative-stress markers and physical function improved, while reported health-related quality of life did not. This is a useful early signal for the combination; the trial neither isolated glycine’s contribution nor measured lifespan. 4

Oxidative stressToo little evidence

Early combination evidence; plain glycine requires separate testing. 4

What about liver and metabolic health?

A metabolism review describes benefits in rodent fatty-liver models. Those experiments justify further research, but do not establish treatment effects in people. 5

Effects by health goal

Open an effect to see the studies behind its rating. Bars show the size of the effect; the letter grades the evidence.

All studies

13 publications are linked to Glycine, newest first.

The effect of glycine administration on the characteristics of physiological systems in human adults: A systematic review2023Supplementing Glycine and N-Acetylcysteine (GlyNAC) in Older Adults Improves Glutathione Deficiency, Oxidative Stress, Mitochondrial Dysfunction, Inflammation, Physical Function, and Aging Hallmarks: A Randomized Clinical Trial.2022Nutritional Modulation of Sleep Latency, Duration, and Efficiency: A Randomized, Repeated-Measures, Double-Blind Deception Study2022Glycine and N‐acetylcysteine (GlyNAC) supplementation in older adults improves glutathione deficiency, oxidative stress, mitochondrial dysfunction, inflammation, insulin resistance, endothelial dysfunction, genotoxicity, muscle strength, and cognition: Results of a pilot clinical trial2021Glycine Metabolism and Its Alterations in Obesity and Metabolic Diseases2019New therapeutic strategy for amino acid medicine: glycine improves the quality of sleep.2012Does Glycine max leaves or Garcinia Cambogia promote weight-loss or lower plasma cholesterol in overweight individuals: a randomized control trial2011Glycine ingestion improves subjective sleep quality in human volunteers, correlating with polysomnographic changes2007Subjective effects of glycine ingestion before bedtime on sleep quality2006L-Glycine: a novel antiinflammatory, immunomodulatory, and cytoprotective agent2003Beneficial effects of glycine (bioglycin) on memory and attention in young and middle-aged adults.1999New therapeutic strategy for amino acid medicine: glycine improves the quality of sleepBeneficial effects of glycine (bioglycin) on memory and attention in young and middle-aged adults

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