Glycine

Glycine is an important part of collagen, the building block of skin and joints.

Glycine is the simplest amino acid and makes up a large share of collagen. FDA lists glycine as GRAS when used in animal feeds under good manufacturing or feeding practice (21 CFR 582.5049). Cats get glycine from meat and can also make it themselves. If your cat has kidney disease or another medical condition, its veterinarian can advise on the diet as a whole.

Source: govinfo.gov

Glycine is added mainly as a flavor and amino acid source. It has a mildly sweet taste and forms a large part of collagen, the protein in skin and connective tissue. The body also uses it to make glutathione, an antioxidant. Most of the glycine in cat food comes from meat, and the added form is a small extra.

Tufts veterinary nutritionists list taurine as an essential nutrient for cats, and glycine is not on their list of essential amino acids. That means a complete cat food has to supply taurine, and glycine does not count toward that need. How cats use each of these amino acids in bile and digestion is a physiology question your veterinarian can explain in more detail.

Source: sites.tufts.edu

No. Glycine is not on the list of essential amino acids for cats, because the body can make it. Tufts veterinary nutritionists list the essential ones as arginine, histidine, isoleucine, leucine, lysine, methionine, cystine, phenylalanine, threonine, tryptophan and valine, plus taurine for cats. AAFCO does not set a glycine minimum for cat food.

Source: sites.tufts.edu

Pettings gives glycine 4 out of 5 and lists it as an amino acid. It appears on 5 of the 149 dry cat foods we list. Few dry foods add it because meat already supplies plenty. Each food's page shows how it scores overall.