Glycine

Glycine is the simplest and smallest non-essential amino acid, serving as a fundamental building block for proteins throughout the human body. While the body can synthesize it from other amino acids like serine, it is also obtained through diet (found in meat, fish, and dairy) or supplementation. It is unique because it acts as both a structural component—comprising approximately 33% of human collagen—and a powerful inhibitory neurotransmitter in the central nervous system. It is also a critical precursor to glutathione, the body’s "master antioxidant," and creatine, which provides energy for muscle cells.