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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

What it is studied for

The strongest rated effects first. Bars show the size of the effect, the letter grades the evidence, and each rating lists the studies behind it.

Sleep qualitySleepModerateB3 studies
Oxidative stressLongevityModerateB2 studies
Liver healthOrgan FunctionModerateB2 studies
Sleep DurationSleepSmallB2 studies
Sleep OnsetSleepSmallB2 studies
Mental EnergyCognitionSmallC2 studies
All 10 rated effectsGrouped by health goal, with the publications behind each rating

Why study an amino acid the body already makes?

Glycine contributes to proteins and glutathione, a substance involved in antioxidant defenses. Lower circulating levels have been observed in obesity and metabolic disease. That association has prompted research, but it does not establish that low glycine causes those conditions or that everyone needs a supplement. 1

Key studies

The most recent publications linked to Glycine's ratings.

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 Diseases2019
All 13 studiesEvery publication linked to Glycine

Why people take it

Essential Health19.1%
Energy14.1%
Fitness12.6%
Immune Support12.3%
Cognition6.6%
Gut Health5.8%

SuppCo community snapshot, 2026-09-28. Reasons for use are not evidence that it works.

Questions people ask

Is glycine an essential amino acid?

The body can make glycine, including from serine; its metabolic importance does not by itself establish a need for supplementation. 1

How much was used in sleep studies?

Several short trials used 3 g before bedtime. That describes research, not a personal dose or a long-term safety limit. 2

Does glycine make up for too little sleep?

The small sleep-restriction experiment measured selected daytime outcomes over three nights; it did not establish that the health consequences of sleep loss were prevented. 3

Are collagen sleep benefits caused by glycine?

That is a plausible explanation discussed in the scoping review, but direct mediation studies have not established it. 4

Can glycine improve every type of attention?

No such conclusion follows from the memory trial: focused and divided attention did not improve. 5

Sources