Glycine

What is it?

It is a cellular specific micronutrient. The most abundant amino acid intracellularly, it is a limiting precursor of glutathione (GSH), collagen and neurotransmitters (glycine inhibits NMDA).

Supplementation forms

It is available on the market mainly in three forms: free glycine in powder or capsules, hydrolyzed collagen or collagen peptides, and gelatin.

Physiological functions

Glycine acts as a key structural component of collagen, where approximately every third waste product is glycine. This allows triple-helix packing and gives resistance and flexibility to skin, tendons, bones, cartilage, and extracellular matrix.

In addition to its structural role, glycine is a precursor of essential molecules such as glutathione (extracellular antioxidant), creatine (muscle and brain function), hemoglobin (oxygen transport), purines (DNA/RNA), and conjugated bile salts (lipid digestion).

In the central nervous system, it acts as an inhibitory neurotransmitter and NMDA receptor coagonist, and various clinical trials have observed that ingesting glycine before going to sleep can improve the subjective perception of sleep quality and reduce daytime drowsiness.

Foods

Glycine is present in nearly all protein foods, but its content is especially high in those rich in collagen and gelatin.

Meat cuts with connective tissue, poultry skin, fish and shellfish, as well as broths and products derived from bones and cartilage. Dairy products, eggs and legumes also supply glycine.