Natural Factors Glycine - Natural Factors Glycine is a source of a non-essential amino acid involved in muscle protein synthesis. Each vegetarian capsule contains 500 mg of glycine, providing 1000 mg daily. Although the body can synthesize some glycine, it is most effective when taken as a free-form amino acid. This formula contains glycine made through natural fermentation. It is non-GMO and suitable for vegetarians and vegans.