L-glycine - 300 GramsL Glycine is a naturally occuring, non essential amino acid that can also be obtained from the diet, primarily in meat, fish and dairy. If you train, supplemental Glycine may be of particular benefit to you. Glycine is the primary amino acid in collagen, the most abundant protein in the human body. It is an integral part of connective tissue, such as bone, skin, ligaments, tendons and cartilage.