Glycine is an amino that is produced through a chemical synthesis. It is the simplest amino with only a single hydrogen atom. The body uses glycine to create proteins, which help with the growth and maintenance, and it also has a function in producing hormones and enzymes. Glycine does not have much nutritional value, so is rarely taken as a supplement. However there is research to suggest that it can help with sleep. It's widest use with in food and pet food is as a flavouring as it has a mildly sweet note.