The term “collagen” is used as a generic term for the proteins that make up the characteristic triple helix of the three polypeptide chains, and all members of the collagen family form specific structures in the extracellular matrix, although they can vary widely in size, function, and tissue distribution.
Collagen is an insoluble protein that is a crucial structural component of connective tissue, including skin, bones, tendons, and cartilage. There are 29 types of collagen, and 80–90% of them are types 1, 2, and 3. Collagen makes up 25–30% of all proteins in the body. In the skin, collagen constitutes up to 75% of its total mass, and it is a component of the extracellular matrix.
The primary function of collagen:
- provides mechanical support,
- in combination with hyaluronic acid and other matrix fibers – reticulin and elastin, collagen forms a support network for fibroblasts, keratinocytes, melanocytes, and specialized cells of the skin’s immune system.
Other functions:
- creates a specific pericellular microenvironment that provides cells with a specific physiological microenvironment, protecting them from harmful mechanical influences, and also mediating mechanically-induced signal transmission,
- contributes to the local storage and delivery of growth factors and cytokines – thus, it plays an essential role in the development of organs, wound healing and tissue repair,
- non-collagen fragments of collagen IV, XV, and XVIII influence angiogenesis and oncogenesis.
With age, the skin’s network of collagen fibers becomes “fragmented” (the fibers are shorter and less organized, accumulating as fragments of degraded collagen). The aging process is also associated with the production of metalloproteinases – enzymes that break down collagen fibers, thus reducing the synthesis of new extracellular matrix components.
As a result of the overlapping of internal and external aging, structural and functional changes occur in the dermis:
- volume reduction,
- elasticity loss,
- thinning of the epidermis,
- wrinkles,
- reduction of the skin’s ability to retain moisture (degradation of hyaluronic acid, which is responsible for water retention in skin structures).
Collagen supplements are available in: powders, capsules, tablets, gummies, liquid forms, and as an ingredient of various cosmetic products. Derived from animal sources, they are in the form of proteins, peptides, gelatin, or hydrolyzate. After denaturation under heat, collagen turns into gelatin. Further hydrolysis results in collagen (CH) hydrolysates, which are water-soluble, non-gelled peptides. Most collagen supplements are CH, which dissolve easily in hot or cold liquids and can be added to food. Vegan collagen is synthesized from genetically modified yeast and bacteria.
Hydrolyzed Collagen (HC), as one of the newest and promising anti-aging supplements, has shown functional and beneficial effects on the skin in several scientific studies. It has been shown to improve the clinical signs of skin aging. Some studies have shown that the oral administration of bioactive collagen peptides can reverse the age-related reduction in collagen synthesis.
Collagen peptides are obtained by enzymatic hydrolysis of natural collagen. After digestion, they are metabolized into dipeptides and tripeptides in the gastrointestinal tract and then transported through the bloodstream and accumulated in the skin to form new collagen fibers.
HC supplements are rich in amino acids:
- hydroxyproline,
- proline,
- glycine.
Among the mentioned proteins, only hydroxyproline is a component of collagen.
Several studies show that prolylhydroxyproline (Pro-Hyp) and hydroxyprolylglycine (Hyp-Gly) are absorbed after ingestion not as amino acids but as dipeptides that are deposited in the skin. Dipeptides increase the bioactivity of skin fibroblasts by increasing collagen synthesis, thus affecting hydration, elasticity, and reduction of wrinkles.
The results of the meta-analysis (de Miranda et al. 2021)
Hydrolyzed collagen supplements or collagen peptides can delay and improve the signs of skin aging by:
- reducting of mimic wrinkles,
- improving hydration,
- improving skin elasticity,
while supplementing. The time of supplementation required to obtain the above benefits is 90 days, and the duration of the effects is 4 weeks after the end of supply. Consuming supplements appears to be effective and safe as no side effects were reported in any analyzed studies. However, more research is needed to evaluate the long-term use of HC peptides. The analyzes so far concerned a maximum of 90 days of supplementation, and the evaluation of the effects lasted 120 days. It is also necessary to thoroughly evaluate the impact of the carrier and other substances administered simultaneously with collagen, mainly vitamins, and coenzyme Q10, which may act synergistically with collagen.
While there are many different types of objective research, it is unclear how supplementation translates into an improvement in clinical appearance or why collagen supplements affected them. Nor is there any credible evidence to suggest that orally digested collagen is preferentially located in the dermis instead of other parts of the body. Some studies argue that the amino acids required for collagen synthesis can be consumed from a standard protein diet, negating the need for additional collagen supplementation. Besides collagen, many other important proteins influence the appearance and properties of the skin.
