Benefits of Glycine and Collagen

Benefits of Glycine and Collagen

Glycine is involved in the synthesis of collagen. Despite being a non-essential amino acid, the research has shown how its intake can improve the production of collagen

Importance of non-essential amino acids

As you may already know, proteins are made up of amino acids.

Traditionally, we have used different criteria to classify them. Apart from their structural differences, amino acids are different in terms of their function on the organism.

Therefore, we can distinguish between:

  • Essential amino acids (EAA’s): those that we CANNOT synthesize and which have to be obtained from the diet.
  • Non-essential amino acids (NEAA’s): those that our body cannot produce on its own.
  • Conditionally essential amino acids (CEAA’s): those that we have to obtain from the diet due to specific physiological conditions or stages.

Usually, we tend to give more importance to the intake of EAA’s, either through food or supplementation. But, what about non-essential amino acids?


Without any doubt, the fact that our body can produce them has made them look less important when it comes to their intake through the diet

Yes, we do have ways of synthesizing them and a low intake will not threaten our survival. However, do we really produce enough quantities of these amino acids in order to meet our demands?

Functions of the NEAA’s

Recently, there have been some studies that talk about the “dietary essentiality” of non-essential amino acids.

This current relies on different research lines that show the lack of efficiency of the endogenous synthesis. Or at least, an inability to produce enough amounts to support all the metabolic functions.

Functions of non essential amino acids

As we can see in the image, these amino acids are involved in many pathways and bodily functions

In fact, some have considered classifying amino acids according to their functional necessities. Therefore, we would not take into account if they are synthesized in the organism or not.

In other words, we would not see “synthesizable amino acids” as “nutritionally non-essential amino acids”.

Example: Amino Acid Arginine

For example, in the 40s, a study proved that following a low-arginine diet reduced the motility and number of spermatozoa in a 90%.

Arginine is a non-essential amino acids. So, if we were capable of producing enough amounts, we would not experience such complications.

This alteration was corrected with supplementation of said amino acid

All in all, what we are trying to defend is that the dietary requirements of amino acids should not only consider if they are synthesized endogenously or no. In fact, it  should take into account its metabolic requirements

The importance of glycine

This amino acid makes up a third part of the structure of collagen, which is the most abundant protein in our organism.

Glycine is another of the NEAA’s which has gotten more attention in the last few years

Apart from its structural functionality (protein synthesis), glycine is a neurotransmitter or precursor of molecules. For instance, some of these molecules are creatine, glutathione or nucleic acids, to name a few.

Glycine deficiency

According to the studies, our body does not produce enough glycine in order to meet all the requirements. This imbalance remains even when we take into account the amount of glycine we can take from the diet.

In a study published by Meléndez-Hevia et al. in 2009, the endogenous synthesis of this amino acid is around 3 grams a day. However, the common supply through the diet is around 2.5g a day.

If we take into account that our body spends around 14.5g a day for the synthesis of metabolites, collagen and other proteins… we would have a deficiency of 8.5g – 10g of glycine every day

Glycine and collagen production

These authors emphasize that even though a glycine deficiency is not lethal or compromises our survival, it is necessary for a proper collagen synthesis.

In fact, the authors defend that a lower amount of glycine in the diet would slow down its regeneration

A relevant aspect that we have observed in some studies is that the intravenous administration of amino acids (glycine) can stimulate the collagen synthesis.

If glycine were not so important, the collagen production should be invariable because we would only used the glycine that our body produces.

Although we produce some amino acids, increasing their availability can improve both the synthesis of proteins and metabolites

Collagen regeneration

The collagen regeneration is one of the most important aspects to treat osteoarthritis.

Supplying the amino acids that make it up (glycine, proline and lysine) can be key when it comes to recovering and preventing this disease

Healthy hip joint vs osteoarthritis

In fact, a study in vitro (Paz-Lugo et al., 2018) concluded that by increasing the availability of glycine, lysine and proline, the chondrocytes (cartilage cells) increased the production of type II collagen fibers.

When they administered other control amino acids (isoleucine and aspartic acid), the collagen synthesis remained stable. Consequently, they concluded that glycine, lysine and proline are absolutely necessary to stimulate its production

Collagen as source of amino acids and peptides

When we take hydrolyzed collagen supplements, our body does not only absorb its constituent amino acids. In fact, only specific di and tripeptides (bonds of 2 or 3 amino acids) enter the bloodstream.

From all of them, the dipeptide Pro-Hyp (proline – hydroxyproline) seems to protect the cartilage. Moreover, it stimulates the cell proliferation and growth or the synthesis of hyaluronic acid depending on the study.

Even the dipeptide Hyp-Gly (hydroxyproline-glycine) from collagen seems to have positive effects.

From what we know, the blood levels of these peptides increase in proportion to the dose. Consequently, we can reach a maximum peak after 2 hours, going back to basal values 6 hours after being consumed.

It is possible that many of the beneficial effects of taking hydrolyzed collagen may be due to these polypeptides, as well as the extra glycine.

Apart from dietary factors, physical exercise can also stimulate the collagen synthesis

Benefits of collagen for athletes

A study observed how taking gelatin (collagenwith vitamin C increased the glycine levels. Moreover, it also increased the constituents of collagen in the blood (proline, hydroxylysine and hydroxyproline).

Increasing the concentrations of these components stimulated the collagen synthesis. In turn, it was also enhanced after doing physical exercise after taking the gelatin.

This could have positive implications in order to improve the post-workout recovery

Study on Athletes

On the other hand, a study conducted on 2008 gathered a group of 147 university athletes (97 completed the study) who usually suffered joint pain and discomfort.

Above all, the objective of the study was to assess the effectiveness of 10g of collagen a day for 24 weeks or a placebo.

Joint Pain Walking or Standing

As we can see, the group that took collagen improved their perception of pain while walking or standing


According to the authors, the group that took collagen supplementation suffered less pain when transporting or lifting objects.

Moreover, they suggested that we will experience its effects after a while, which is why it is so important to take them regularly.

There are other studies that suggest that the relief from collagen has reduced the intake of analgesics

Collagen and benefits for the skin

Collagen and elastin fibers weaken with the passing of time. Consequently, this results in the onset of expression lines and wrinkles. In addition, we also lose glycosaminoglycans and hyaluronic acid, making our skin less hydrated.

Therefore, an extra collagen supply and other nutrients could counter these symptoms associated with aging

Symptoms of aging

It is not secret that age affects the connective tissue, both from the cartilage as well as the skin

Recent study

A double blind, placebo controlled study (Czajka et al., 2018) used a combination of: hydrolyzed collagen, glucosamine, hyaluronic acid, chondroitin sulfate and other active ingredients, vitamins and minerals.

Above all, they assessed its effects on the health and aspect of the skin:

Test product vs placebo

For 90 days, the group that took the supplementation have a more elastic skin, which did not happen to the placebo group


Moreover, they authors also highlighted a better joint health, which resulted in less joint pain, more flexibility and motility and less rigidity.

Elasticity chart

The participants also pointed out a better feeling of well-being and vitality when taking the supplement but not the placebo

However, the biggest limitation of this study was the source of funding. Although we should not give less importance to the results just because of that.


Traditionally, we have not given enough important to those amino acids that we can produce, known as non-essential amino acids.

Several studies have proven that the fact the our body can synthesize them does not mean that we can meet the requirements completely.

One of the most common cases is that of glycine, which is involved in many vital functions, the most important being the collagen synthesis

A glycine deficiency has been related to motor and growth problems. Its intake through the diet has proven to be effective to stimulate the collagen synthesis.

Proline and hydroxyproline is another of the amino acids that make up the collagen molecules. Moreover, it also plays important functions in the organism.

Taking collagen provides many benefits for joint health, both for athletes and the general population

Joint pain

It could even help us reduce the consumption of painkillers

There is much left to investigate and many of the studies that support collagen have a important conflicts of interest. However, due to the safety of these supplements and their potential benefits, they are a great choice when it comes to improve the joint and skin health.

Beyond collagen and glycine, due to the importance of non-essential amino acids, we should reformulate the concept of complete protein, which has been exclusively connected to essential amino acids up until now


  1. Clark et al., 2008. 24-week study on the use of collagen hydrolysate as a dietary supplement in athletes with activity-related joint pain.
  2. Czajka et al., 2018. Daily oral supplementation with collagen peptides combined with vitamins and other bioactive compounds improves skin elasticity and has a beneficial effect on joint and general wellbeing.
  3. Daneault et al., (2015). Biological effect of hydrolyzed collagen on bone metabolism.
  4. Hou et al., (2015). Dietary essentiality of “nutritionally non-essential amino acids” for animals and humans.
  5. Meléndez-Hevia et al., (2009). A weak link in metabolism: the matabolic capacity for glycine biosinthesis does not satisfy the need for collagen synthesis.
  6. Moskowitz (2000). Role of collagen hydrolysate in bone and joint disease.
  7. Paz-Lugo (2018). High glycine concentration increases collagen synthesis by articular chondrocytes in vitro: acute glycine deficiency could be an important cause of osteoarthritis.
  8. Razak et al., (2017). Multifarious beneficial effect of nonessential amino acid, Glycine: a review.
  9. Shaw et al., (2017). Vitamin C-enriched gelatin supplementation before intermittent activity augments collagen synthesis.
  10. Shigemura et al., (2014). Dose-dependent changes in the levels of free and peptide forms of hydroxyproline in human plasma after collagen hydrolysate ingestion.
  11. Wang et al., (2013). Glycine metabolism in animals and humans: implications for nutrition and health.
  12. Wu et al., (2013). Dietary requirements of “nutritionally non-essential amino acids” by animals and humans.

Related Entries

  • Read more about hydrolyzed collagen.
  • Physical exercise and collagen – Read this article
  • Tips to take collagen, find out more
  • Click here to find out more about collagen and magnesium
  • Click here to learn about the different types of collagen
  • Do you know everything about collagen? Read this post to learn about its uses
Collagen and Glycine

Supporting the Collagen Production - 100%

Supporting Joint Health - 100%

Improving the Collagen Synthesis - 99%

Taking Glycine is Essential - 100%


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About Carlos Sánchez
Carlos Sánchez
Carlos Sánchez has a degree in Human Nutrition and Dietetics, and therefore all his actions are rigorously backed by science.
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