Glycine and Muscle Loss
Very few studies exist on supplementation with the amino acid glycine in humans. In rats it appears to prevent muscle loss when compared to alanine, another amino acid. It is unclear if this effect is relevant in humans, or if it exists when already supplementing with other protein supplements. Maria Ekblom gives us the details below!
Glycine is a non-essential amino acid, meaning the body can produce it on its own, and therefore not essential to the human diet. It serves as a neurotransmitter and is used for treating diseases like schizophrenia and stroke. It appears to exert several protective effects, and some studies indicate that it could be an effective anti-inflammatory agent. Its use as a supplement has increased rapidly the last decade and retailers claim glycine to be involved in muscle growth etc.
What can be said about glycine is that there are very few studies on human subjects. Current scientific evidence comes mostly from studies on rats and pigs.
Mice Given Glycine In a Caloric Deficit
A study performed on mice presented glycine as a potential protector against cancer-induced muscle loss and muscle protein breakdown. The study also concluded that these effects were glycine-specific (1).
Mice supplemented with glycine during calorie restriction had reduced fat-mass and a larger preservation of muscle mass compared to mice supplemented with alanine (2). A newly published review demonstrated the same result, that supplemental glycine effectively protected the muscle in a variety of wasting models, like reduced caloric intake (3).
Limiting Inflammation?
The mechanism by which glycine exerts its protective effects on the muscle during calorie restriction is not clear but it is likely to include reduced inflammatory cell activation and subsequent production of cytokines and free radicals.
Thus, glycine supplementation appears to improve loss of fat mass and reduce loss of skeletal muscle during calorie restriction. As mentioned, the evidence is largely based on animal model studies.
Since the underlying mechanisms responsible for the effects of glycine remain unclear, future research is needed to provide insight in glycine’s true potential. Further questions that need to be answered are if glycine is more effective than any other supplement and can its potentially preserving effects of skeletal muscle be counted on when combined with other supplements?
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Article by Maria Eklbom. Licensed physiotherapist and personal trainer.
Sources:
- Ham D, Murphy K, Chee A, Lynch G, Koopman R. Glycine administration attenuates skeletal muscle wasting in a mouse model of cancer cachexia. Clinical Nutrition. 2014;33(3):448-458.
- Caldow M, Ham D, Godeassi D, Chee A, Lynch G, Koopman R. Glycine supplementation during calorie restriction accelerates fat loss and protects against further muscle loss in obese mice. Clinical Nutrition. 2016;35(5):1118-1126.
- Koopman R, Caldow M, Ham D, Lynch G. Glycine metabolism in skeletal muscle. Current Opinion in Clinical Nutrition and Metabolic Care. 2017;20(4):237-242.
