Glycine
Glycine is the smallest amino acid and one of glutathione's three building blocks. It also makes up a third of the amino acids in collagen, so cartilage cells need it for both their antioxidant and their matrix.
Also called L-glycine, Gly.
The body makes glycine, mostly from another amino acid, serine. One analysis estimated that an adult makes about 3 g a day and gets 1.5 to 3 g from food, which may fall about 10 g a day short of all its uses, collagen included, and argued that glycine should be treated as semi-essential (Meléndez-Hevia 2009).
In cow cartilage cells in the lab, raising glycine above 1 mM increased type II collagen production by 60 to 75%, a larger and longer-lasting effect than proline or lysine (de Paz-Lugo 2018).
For glutathione, older adults had lower red-cell glycine than younger adults, and two weeks of glycine with cysteine restored their glutathione synthesis (Sekhar 2011). Glycine paired with NAC is the GlyNAC combination tested in later trials in older adults (Kumar 2021; Kumar 2023).
Sources
- Meléndez-Hevia E, De Paz-Lugo P, Cornish-Bowden A et al. A weak link in metabolism: the metabolic capacity for glycine biosynthesis does not satisfy the need for collagen synthesis. J Biosci 2009.
- de Paz-Lugo P, Lupiáñez JA, Meléndez-Hevia E. High glycine concentration increases collagen synthesis by articular chondrocytes in vitro: acute glycine deficiency could be an important cause of osteoarthritis. Amino Acids 2018.
- Sekhar RV, Patel SG, Guthikonda AP et al. Deficient synthesis of glutathione underlies oxidative stress in aging and can be corrected by dietary cysteine and glycine supplementation. Am J Clin Nutr 2011.
- Kumar P, Liu C, Hsu JW et al. Glycine and N-acetylcysteine (GlyNAC) supplementation in older adults improves glutathione deficiency, oxidative stress, mitochondrial dysfunction, inflammation, insulin resistance, endothelial dysfunction, genotoxicity, muscle strength, and cognition: Results of a pilot clinical trial. Clin Transl Med 2021.
- Kumar P, Liu C, Suliburk J et al. Supplementing Glycine and N-Acetylcysteine (GlyNAC) in Older Adults Improves Glutathione Deficiency, Oxidative Stress, Mitochondrial Dysfunction, Inflammation, Physical Function, and Aging Hallmarks: A Randomized Clinical Trial. J Gerontol A Biol Sci Med Sci 2023.
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