Glycine supplements for athletic performance and recovery
What it found
Glycine supplements may help muscle strength, recovery and sleep, but most evidence comes from lab and animal studies.
Human trials are still scarce.
What they found
Studies in people
Muscle strength in people
In a randomized trial, older adults took glycine and N-acetylcysteine for 24 weeks. They had less inflammation, better strength and exercise capacity, and lower body fat. These benefits faded after stopping for 12 weeks.
Marathon runners
In a randomized study, marathon runners took 10 g of glycine three times a day for 14 days before a race. Muscle tissue injury after the race and 48 hours later was similar with or without glycine.
Sleep quality
Human studies found that 3 g of glycine before bedtime improved sleep quality, daytime sleepiness and fatigue in healthy men and people with difficulty sleeping.
Animal and lab studies
Muscle wasting in animals
Animal studies suggest glycine may protect against muscle wasting during high-stress conditions like cancer cachexia and sepsis. It activates anabolic pathways and inhibits proteolytic gene expression.
Collagen in lab tests
In cultured bovine chondrocytes, high glycine concentrations increased type 2 collagen synthesis by 2.5 times. This suggests a potential role in muscle repair after injury or strenuous exercise.
High-dose risks
High doses of glycine (more than 500 mg per kg of body mass) may cause kidney and liver cell damage and contribute to acute toxicity in the brain, leading to neuronal death.
What the authors conclude
“It is concluded that more randomized controlled clinical trials in humans are needed to confirm glycine's potential as a dietary supplement to support muscle function, recovery, and overall athletic performance as an ergogenic aid and to establish nutritional recommendations for athletic performance.”
Also in their conclusions
- They conclude that more randomized controlled clinical trials in humans are needed to confirm glycine's potential as a dietary supplement to support muscle function, recovery, and overall athletic performance.
- They call on the scientific community to prioritize well-designed, randomized, controlled trials investigating the effects of glycine supplementation on physical performance, muscle strength, recovery, and sleep quality in the human population.
- They advise that high doses (>500 mg/kg of body mass) could induce cytotoxic effects and contribute to acute glutamate toxicity.
How it was done
Athletes often take glycine supplements, but there are no statistics on how much is consumed or how it affects athletic performance. The authors wanted to see if the gap between lab findings and real-world effects could be bridged.
The authors reviewed published studies on glycine supplementation, including cell, animal and human research. They looked at effects on muscle strength, regeneration, endurance, sleep and recovery.
What it can’t tell you
- Most of the effects described come from animal models, isolated cells, and tissues, so they may not apply to people.
- There is not enough evidence to establish dietary recommendations for athletic performance.
- Human studies are scarce and often combine glycine with other supplements, making it hard to isolate its effects.
Who paid
- Funding
- Funded by Asociación Universitaria Iberoamericana de Postgrado; Consorcio de Universidades Mexicanas (CUMex) (from the PubMed record).
- Conflicts
- The authors declare no conflicts of interest.
- Authors work at
- Conahcyt National Laboratory of Body Composition and Energetic Metabolism (LaNCoCoME), Mexico; Autonomous University of Ciudad Juarez, Mexico; Autonomous University of Chihuahua, Mexico
The paper
- Title
- An Update of the Promise of Glycine Supplementation for Enhancing Physical Performance and Recovery
- Type
- ReviewThe authors read earlier studies and describe what they found. It isn’t a new study.
- Evidence
- Studies in people · animals · lab
- Summarised from
- Full text
- Cite
- Ramos-Jiménez A, Hernández-Torres RP, Hernández-Ontiveros DA, et al (2024). An Update of the Promise of Glycine Supplementation for Enhancing Physical Performance and Recovery. Sports (Basel, Switzerland). doi:10.3390/sports12100265Free full textPubMed 39453231DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error