Glycine: A simple amino acid with an important role in creatine synthesis. Does supplementation make sense for athletic performance?

Glycine is a non-essential amino acid and, in terms of chemical structure, the simplest of all 20 amino acids commonly found in proteins. Although the body can synthesise it on its own, it plays several specific roles in an athlete's body. But does supplementing it matter for sports performance?

Key functions in metabolism

Glycine is an essential building block for the synthesis of other substances that directly influence muscle energy metabolism:

Manufacturers' claims vs scientific evidence

In the sports supplement segment, glycine is credited with increasing phosphocreatine synthesis, improving sprint performance and boosting maximal strength. These claims, however, rest on very weak foundations:

Conclusion for athletes

Although glycine is indispensable for the natural production of creatine and for protecting cells, supplementing it in isolated form demonstrably does not lead to better sports results. Athletes are better off focusing on a sufficient intake of proteins with a complete amino acid profile, which naturally contain glycine. If the goal is greater strength and explosiveness, the more scientifically supported choice is direct creatine supplementation.

1. Jeukendrup A, Gleeson M. (2025). Sport nutrition (4th ed.). Human Kinetics.