Glycine is the simplest amino acid. The body makes it, so it is not an essential nutrient, and it also acts as a signaling molecule in the brain and spinal cord.
Also known as: aminoacetic acid.
Glycine has no Recommended Dietary Allowance or upper limit, because it is a non-essential amino acid. Supplements are usually sold as powder or capsules.
It is sold in the US as a dietary supplement. Under the 1994 dietary supplement law (DSHEA), FDA does not approve dietary supplements before they are marketed, and the maker, not FDA, is responsible for safety and labeling. In food, FDA regulates glycine as a food additive (21 CFR 172.812) for limited technical uses, such as masking the aftertaste of saccharin in drinks at no more than 0.2%. The FDA-approved drug form is 1.5% glycine irrigation solution, used to rinse the bladder during prostate surgery, not a pill.
In a small study of healthy people, 1 mmol per kg of lean body mass of glycine taken with 25 g of glucose cut the rise in blood sugar by more than half compared with glucose alone (Gannon 2002). This is a single physiology study, not evidence of a treatment effect.
The only human half-life we found comes from glycine given by vein or absorbed during surgery (Hahn 1993): it ranged tenfold, from 26 to 245 minutes, and rose with the amount given. There is no published time to peak for glycine taken by mouth that we could confirm. Because the half-life depends so strongly on dose and route, we do not list the app's 1-hour and 30-minute modeling values.