Evidence supporting the use of: L-glycine
For the health condition: Exercise

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Synopsis

Source of validity: Scientific
Rating (out of 5): 2

L-glycine is a non-essential amino acid that plays several roles in human physiology, including as a building block for proteins, a precursor for biosynthesis of key biological compounds (such as creatine and glutathione), and as an inhibitory neurotransmitter. Its use in supporting or treating exercise performance and recovery has some scientific basis, though the evidence is still emerging and not robust.

Research suggests glycine supplementation may help reduce inflammation and oxidative stress related to intense exercise, potentially improving recovery. For example, animal studies have demonstrated that glycine can mitigate muscle damage and oxidative markers following exhaustive exercise. A few small human studies indicate that glycine, often in combination with other amino acids, could lower markers of muscle damage and support immune function post-exercise. Additionally, glycine’s role as a precursor to creatine and glutathione may theoretically benefit exercise performance and recovery, as both compounds are known to support energy metabolism and cellular defense mechanisms in active muscles.

However, the direct evidence for glycine alone enhancing exercise performance, endurance, or muscle growth in humans is limited and not as strong as for other amino acids like leucine or creatine. Most available studies are small, preliminary, or use multi-ingredient formulas. Therefore, while there is some scientific rationale and emerging evidence, the overall strength of evidence supporting glycine specifically for exercise support is modest and warrants further research.

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