Glycine is an amino acid used by the body to make proteins and several other important compounds. It is the smallest amino acid and is particularly prominent in collagen, where its size allows collagen’s three protein chains to fit closely together.
The body can normally produce glycine, and it is also available from protein-containing foods. Glycine supplements are sold separately, but they should not be confused with collagen peptides, which contain glycine as part of a much broader amino-acid profile.
This guide explains what glycine does, where it comes from and why it is so closely associated with collagen.
What Is Glycine?
Glycine is one of the amino acids used to build proteins. Amino acids join together to create chains called peptides. Longer chains can then fold into proteins with different structures and functions.
What makes glycine unusual is its very small and simple structure. Its side chain consists of a single hydrogen atom, making it smaller than the other amino acids commonly found in proteins.
This small size allows glycine to fit into tightly packed areas of certain protein structures. That is particularly important in collagen.
Is Glycine an Essential Amino Acid?
Glycine is generally classified as a non-essential amino acid because the body can make it from other compounds. It does not normally need to be obtained entirely through food.
In nutritional terminology, “non-essential” does not mean unnecessary. It simply means the body is capable of producing the amino acid. Glycine can also be described as conditionally essential in some scientific discussions. This means the body’s own production may not always match its requirements under certain physiological circumstances.
For most people, however, glycine is obtained through a combination of the body’s own production and an ordinary varied diet.
What Does Glycine Do in the Body?
Glycine has several established biochemical functions. It contributes to proteins and is also used when the body produces other compounds.
Glycine Helps Form Proteins
Glycine is incorporated into many different proteins. Its effect on a protein depends on where it appears within the amino-acid chain and how that chain folds. It is especially prominent in collagen but is not exclusive to it. Glycine can also be found in proteins obtained from meat, fish, dairy products, eggs and plant-based foods.
Glycine Is a Major Amino Acid in Collagen
Collagen has a distinctive repeating amino-acid sequence. Glycine appears at every third position, while the other positions are frequently occupied by proline and hydroxyproline.
This arrangement is commonly written as Gly-X-Y:
- Gly represents glycine
- X is frequently proline
- Y is frequently hydroxyproline
Three collagen protein chains wind together to create a triple helix. Glycine’s small size allows it to fit within the closely packed centre of this structure.
Scientific research into the collagen triple helix explains why glycine is required at every third position and why replacing it with a larger amino acid can disrupt the structure.
You can see how glycine compares with proline, hydroxyproline and the other amino acids in collagen’s amino-acid profile.
Glycine Contributes to Glutathione
Glycine is one of three amino acids used by the body to produce glutathione. The other two are cysteine and glutamate. Glutathione is involved in the body’s antioxidant systems. However, knowing that glycine contributes to glutathione does not prove that taking additional glycine automatically increases antioxidant protection or prevents disease.
The body’s production of glutathione depends on several biological and nutritional factors rather than one amino acid in isolation.
Glycine Contributes to Creatine
The body also uses glycine when producing creatine, alongside arginine and methionine. Creatine helps transfer energy within cells and is particularly relevant to tissues with changing energy demands. However, glycine should not be treated as equivalent to a finished creatine supplement.
Consuming one of creatine’s starting materials does not necessarily have the same effect as consuming creatine itself.
Glycine Acts as a Neurotransmitter
Glycine also functions as a neurotransmitter, meaning it participates in communication between nerve cells. It acts mainly as an inhibitory neurotransmitter in areas including the spinal cord and brainstem. Glycine is also involved in the activity of certain receptors elsewhere in the nervous system.
This is a complex biological role and should not be interpreted as evidence that a shop-bought glycine supplement can treat neurological or mental-health conditions.
Glycine Contributes to Other Compounds
The body uses glycine in several additional metabolic processes. These include the production of compounds involved in genetic material and haem, the iron-containing component of haemoglobin.
These functions demonstrate that glycine participates in normal human metabolism. They do not, on their own, establish a need for most people to take an isolated glycine supplement.
Why Is Glycine So Prominent in Collagen?
The importance of glycine in collagen comes from its size and repeated position within the collagen protein. A collagen chain follows a recurring pattern in which glycine occupies every third position. This allows three separate chains to wind tightly around one another.
Larger amino acids would take up too much space in the centre of the triple helix. Glycine’s single-hydrogen side chain allows the structure to pack together more closely. This is why collagen proteins typically have a higher proportion of glycine than many other dietary proteins.
The hydrolysed bovine collagen ingredient used in Beauvyn has a typical glycine value of 24.1g per 100g. This is a product-specific analytical value and should not be treated as a universal percentage for every collagen ingredient.
Which Foods Contain Glycine?
Glycine occurs in a wide variety of protein-containing foods.
Sources can include:
- Meat and poultry
- Fish
- Dairy products
- Eggs
- Soya products
- Beans and lentils
- Nuts and seeds
- Gelatine
- Collagen-containing foods
Animal connective tissues, gelatine and collagen are particularly associated with glycine because of collagen’s naturally glycine-rich structure.
Plant foods also contain glycine as part of their proteins, although their amino-acid profiles differ from those of collagen.
The quantity supplied depends on the food, portion size and preparation method. A varied diet contributes multiple amino acids rather than supplying only glycine.
A separate guide to glycine-rich foods will examine animal, plant and vegetarian sources in greater detail.
Does the Body Make Glycine?
Yes. The body can synthesise glycine through several metabolic pathways.
One important route involves the conversion of the amino acid serine into glycine. Other substances can also contribute to its production.
Because the body can make glycine, no standard daily dietary requirement has been established for healthy adults in the same way as it has for essential amino acids.
Individual requirements and production may nevertheless vary with factors such as age, diet and health. This does not mean everyone needs to take additional glycine.
Glycine Supplements and Collagen Peptides
Glycine supplements and collagen peptides are not the same thing.
An isolated glycine supplement normally contains free-form glycine as its main active ingredient. Collagen peptides contain numerous amino acids joined together in short chains.
Collagen peptides characteristically contain:
- Glycine
- Proline
- Hydroxyproline
- Alanine
- Arginine
- Glutamic acid
- Aspartic acid
- Several other amino acids in smaller amounts
During digestion, collagen peptides are broken down further. Research indicates that collagen hydrolysate can be absorbed as free amino acids as well as certain small peptides. A review of collagen protein digestion and absorption discusses the available evidence.
Beauvyn is therefore not an isolated glycine supplement. It contains hydrolysed bovine collagen peptides with the broader amino-acid profile naturally associated with collagen.
What Are the Potential Benefits of Glycine Supplements?
Glycine supplements have been investigated in relation to areas including sleep, metabolism and antioxidant production. However, the strength of the evidence varies considerably.
Some small human studies have examined glycine before bedtime, but limited participant numbers and short study periods make it difficult to draw broad conclusions. Research into metabolic effects has also used specific doses and controlled conditions that should not be generalised to ordinary food or collagen consumption.
Reviews of glycine metabolism and supplementation discuss a wide range of possible applications, but many proposed effects are based on laboratory studies, animal research or limited human evidence.
It is therefore more accurate to distinguish between:
- Glycine’s established functions in normal human biochemistry
- Associations observed in research
- Benefits proven to result from taking an isolated supplement
These are not necessarily the same thing.
Do You Need a Glycine Supplement?
Most people obtain glycine through a combination of dietary protein and the body’s own production.
Whether an isolated supplement is appropriate depends on individual circumstances. A balanced diet normally supplies a range of essential and non-essential amino acids rather than focusing on one compound.
Anyone considering high-dose glycine because of a health condition, medication or suspected nutritional deficiency should speak with a qualified healthcare professional.
Pregnant or breastfeeding people and those receiving medical treatment should also obtain individual advice before introducing a concentrated amino-acid supplement.
Is Glycine Safe?
Glycine consumed as part of an ordinary balanced diet is a normal dietary amino acid.
Supplement products provide more concentrated amounts and may not be appropriate for everyone. Reported digestive effects can include nausea, stomach discomfort or loose stools, particularly at larger doses.
The absence of serious effects in a small or short study does not establish the safety of every dose for every person. Follow the product instructions and seek professional advice when individual health circumstances may affect suitability.
Frequently Asked Questions
What is glycine good for?
Glycine is used by the body to form proteins and compounds including collagen, glutathione, creatine and haem.
These established functions do not mean that taking additional glycine has been proven to produce a particular health benefit in every person.
Is glycine an amino acid?
Yes. Glycine is the smallest amino acid commonly incorporated into proteins.
Is glycine essential?
Glycine is normally classified as non-essential because the body can produce it. It may be described as conditionally essential in certain physiological circumstances.
Is glycine found in collagen?
Yes. Glycine is one of collagen’s most prominent amino acids and appears at every third position in its characteristic protein sequence.
Is glycine the same as collagen?
No. Glycine is one individual amino acid. Collagen is a protein containing glycine alongside proline, hydroxyproline and numerous other amino acids.
Does collagen powder contain glycine?
Yes. Hydrolysed collagen powder naturally contains glycine within its peptide chains. The precise amount varies between collagen sources and ingredients.
What is the difference between glycine and a glycine supplement?
Glycine is the amino acid itself. A glycine supplement is a concentrated product designed to provide isolated or free-form glycine.
Can vegetarians get glycine?
Yes. Dairy products, eggs, soya, beans, lentils, nuts, seeds and grains can all contribute glycine. People following a vegan diet can obtain it from plant-based protein sources.
Is glycine a BCAA?
No. The three branched-chain amino acids are leucine, isoleucine and valine. Glycine has a different chemical structure and is not a BCAA.
The Final Say
Glycine is a small amino acid with several established functions. The body uses it when forming proteins and compounds including collagen, glutathione and creatine.
Its particularly high concentration in collagen is not accidental. Glycine’s small structure enables collagen’s three protein chains to fit closely together in their characteristic triple helix.
However, glycine’s biological importance should not be confused with proof that everyone needs an isolated supplement. Most people obtain glycine through food and the body’s own production, while collagen peptides provide glycine as part of a much wider amino-acid profile.
