Glycine is made in three main ways: your body synthesizes it from other amino acids, factories produce it through chemical reactions, and it can be extracted from animal proteins like collagen. The method depends on whether we’re talking about the glycine circulating in your bloodstream right now or the white powder sold as a supplement or food additive.
How Your Body Makes Glycine
Your body produces roughly 3 grams of glycine per day, accounting for about 35% of all the glycine available to you. The rest comes from food. The primary route is a conversion from serine, another amino acid, using an enzyme called serine hydroxymethyltransferase (SHMT). This enzyme strips a single carbon atom from serine and attaches it to a helper molecule in the folate cycle, leaving glycine behind. The reaction happens in both the main body of cells and in the mitochondria, the energy-producing compartments inside them.
This conversion is reversible, meaning the enzyme can also turn glycine back into serine when the body needs it. The direction the reaction runs depends on what the cell needs at that moment. When levels of certain folate-related molecules drop, the enzyme shifts toward producing more glycine. A downstream product in the folate cycle can also act as a brake, inhibiting the enzyme to prevent overproduction. This feedback system keeps glycine levels in a functional range without conscious effort on your part.
About 87% of endogenously produced glycine comes through this serine pathway. A smaller share comes from other routes. The amino acid threonine can be split into glycine and a two-carbon fragment by a different enzyme. Glyoxylate, a small molecule generated during normal metabolism, can also be converted to glycine by swapping an amino group from alanine onto it, a reaction that requires vitamin B6 as a helper.
The Main Industrial Process
Most commercially available glycine is manufactured by reacting chloroacetic acid with ammonia. In this process, a large excess of aqueous ammonia is mixed with chloroacetic acid, the acid dissolves, and the mixture sits at room temperature for about 48 hours. During that time, the ammonia displaces the chlorine atom on the acid molecule and takes its place, forming glycine. The long reaction time and mild temperature make this a relatively straightforward process at industrial scale, though it requires careful handling of the corrosive starting materials and generates ammonium chloride as a byproduct that must be separated out.
The resulting glycine is then purified and graded. Food-grade glycine (FCC standard) and pharmaceutical-grade glycine (USP standard) both require purity levels of 99% or higher, measured on an anhydrous basis. These strict standards ensure the product is safe for use in supplements, foods, and medications.
The Strecker Synthesis
A second industrial method, the Strecker reaction, has been used since 1850. It starts with formaldehyde, ammonium chloride, and a cyanide source (typically potassium cyanide). The formaldehyde and ammonia combine first, then react with cyanide to form an intermediate called an alpha-aminonitrile. That intermediate is then broken apart with a strong base like sodium hydroxide, yielding glycine. The reaction is efficient but involves hydrogen cyanide or cyanide salts, which are extremely toxic, so it demands rigorous safety controls and is less commonly used today for food-grade production than the chloroacetic acid method.
Extraction From Animal Protein
Glycine can also be obtained by breaking down collagen, the most abundant protein in animal bodies. Collagen is unusually rich in glycine: roughly every third amino acid in its chain is glycine. When collagen from animal skin, bones, or connective tissue is hydrolyzed (broken into its component amino acids using heat, acid, or enzymes), the resulting mixture contains about 27% glycine by amino acid content. Gelatin, the partially broken-down form of collagen used in food products, retains this high glycine proportion.
Extraction from bovine skin, for example, can be enhanced with enzyme pretreatment and ultrasound at 60°C over several hours, which increases both yield and quality. While this method produces glycine mixed with many other amino acids rather than in pure form, it’s the basis for collagen and gelatin supplements that deliver glycine as part of a broader amino acid profile.
Why the Source Matters
If you’re buying glycine as a supplement, it almost certainly comes from the chloroacetic acid process. It’s the cheapest and most scalable method, and the final product is chemically identical to the glycine your body makes. Collagen-derived glycine arrives bundled with other amino acids, which may or may not be what you want depending on your goal. Your body’s own production, while substantial at 3 grams daily, may not fully cover demand during periods of high collagen turnover, wound healing, or intense physical activity, which is one reason glycine supplementation has drawn interest in sports nutrition and recovery research.
Regardless of the source, all glycine ends up as the same molecule: the smallest amino acid, with just two carbon atoms, one nitrogen, and no side chain to speak of. The differences between sources are about purity, cost, and what else comes along for the ride.