From the Guidelines
Glycine does help prevent muscle loss, but the most recent and highest quality evidence suggests that other amino acids, such as glutamine and beta-hydroxy-beta-methylbutyrate (HMB), may be more effective in preventing muscle loss, especially in critically ill patients or those undergoing surgery. The ESPEN guidelines on parenteral nutrition in intensive care recommend the use of glutamine-containing dipeptides, such as alanyl-glutamine, to restore or enhance the content of parenteral nutrition amino acid solutions 1. Additionally, a study on perioperative nutrition found that HMB supplementation resulted in a significant reduction in muscle loss associated with bedrest and an increase in muscle mass gain during the rehabilitation phase 1. While glycine may have some benefits in preventing muscle loss, the evidence is not as strong as it is for other amino acids, and more research is needed to fully understand its effects. It is also important to note that adequate protein intake and regular resistance exercise remain the most important factors for muscle maintenance, and supplements should complement rather than replace these essential components of muscle health.
From the Research
Glycine and Muscle Loss Prevention
- Glycine supplementation has been shown to help prevent muscle loss in various studies 2, 3, 4.
- A study published in 2016 found that glycine supplementation during calorie restriction accelerated fat loss and protected against further muscle loss in obese mice 2.
- Another study published in 2024 suggested that glycine supplementation may enhance peak power output, reduce lactic acid accumulation during high-intensity exercise, and improve sleep quality and recovery 3.
- Glycine administration has also been shown to attenuate skeletal muscle wasting in a mouse model of cancer cachexia 4.
Mechanisms of Glycine's Effects
- Glycine may help prevent muscle loss by activating anabolic pathways and inhibiting proteolytic gene expression 3.
- It may also reduce inflammation and oxidative stress, which can contribute to muscle wasting 4.
- Additionally, glycine may help preserve muscle mass by reducing the expression of genes associated with muscle protein breakdown 4.
Comparison to Other Amino Acids
- Preliminary studies have shown that the protective effect of glycine on muscle wasting is specific to glycine, and not seen with isonitrogenous doses of alanine or citrulline 4.
- Another study found that glycine treated mice lost more whole-body fat mass and epididymal fat mass, and less lean mass, compared to mice treated with l-alanine 2.
Limitations and Future Research
- 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 3.
- High doses of glycine (>500 mg/kg of body mass) could induce cytotoxic effects and contribute to acute glutamate toxicity 3.