The truth behind Collagen peptides

Collagen is the most abundant insoluble protein in animals, it is found in the extracellular space of connective tissue, it comprises three peptide chains that bundle together forming the distinct triple left-handed helix shape of collagen. 
The triple chain, Tropocollagen, is a supercoil with a diameter of 1.4nm and made up of 3 helices, each helix comprises around 1000 amino acid residues.

The three amino acids characteristic in the repeating units of collagen helix are glycine, proline, and hydroxyproline. The triple-helix motif is Gly-Y-X, where Y can either be proline or hydroxyproline, and X can be any other amino acid. Each collagen unit has 3.3 residues per turn and 0.54nm distance per pitch. The three-stranded helices are held together by the hydrogen bond between NH glycine hydrogen and C=O of the adjacent polypeptide. The angle of C-N peptidyl-proline or peptidyl-hydroxyproline is fixed, which makes the three peptide chains fold into a helix (Lodish H, 2000). 

Cells and tissues in mammals are supported by collagen network; there are at least 16 types of collagen, about 80 to 90% of our body consists of three common types of collagen I, II and III collagen.

Type I collagen mostly found in bone (main component of the organic part of bone), dermis, tendon, ligaments and cornea. Type II collagen is found in cartilage, vitreous body, nucleus pulposus, and type III collagen found in tissues of the skin, vessel wall, reticular fibers of most tissues (lungs, liver, spleen, etc.) (Gelse, 2003).

Data in the figure obtained from (Buehler, 2006)

It is hard to study collagen metabolism; studies show that the triple-helical molecules are extracted by secretory vesicles from the Golgi compartment into the extracellular space. The triple helix is cleaved by proteases (N and C) according to the type of the produced collagen, both proteases (N and C), are Zn dependent. The process of cleavage requires the presence of copper and vitamin C as well, yet all data suggests that it is hard to study collagen metabolism because it turns over slowly (Gelse, 2003).

Aging decreases the amount of collagen that reaches the extracellular space, In addition the degradation of tropocollagen by extracellular proteases leaves behind N- and C- terminal fragments that accelerate the breaking down of collagen by metalloproteinases matrix (MMPs) (Rennie, 1999).

But can the oral intake of collagen peptide restore body collagen?

Exploring the extent of collagen consumption is essential to comprehend the possibilities of collagen to reach the extracellular space when orally consumed.

The main questions would be; does the collagen peptide consumed orally reaches skin and bone? Does the digestion process affect the integrity of the collagen peptide?

Skin collagen degrades by metalloproteinases matrix (MMPs), topically administration of collagen peptide (CH) delays aging, and treats the skin. The benefit of ingestion collagen peptide remains obscure, the clinical community agreed on the fact that ingestion of collagen in its hydrolyzed form suppresses the MMP2 activities leading to a reduction of wrinkles (Zague, 2011), still extensive studies were needed to establish concrete results.

Studies that investigated the integrity of the ingestion of peptide showed that collagen hydrolysate can cross the intestinal barrier reaching blood circulation, and becomes available for the metabolic process, and storage in the skin. In fact, the ingestion of a rich collagen diet promotes skin elasticity, reduces pain for people suffering from osteoarthritis, inhabit cardiovascular damage and collagen driven from fish has potent anti-oxidative effect. Collagen hydrolysate supplements proved to relieve joints pain due to heavy exercises in athletes. (Clark, 2008).

A double-blind placebo-controlled trial conducted on 69 women, aged between 35 and 55, for 8 weeks, showed that the oral intake of collagen hydrolysate enhances the skin elasticity, and acts as a skin moisturizer in the elderly women (Proksch, 2014).

An interesting study on rats showed that oral intake of collagen peptide in the presence and absence of calcium diet, both increase the bone mass in rats. The rates with high collagen intake exhibited hypertrophy in kidneys, without undesirable effects. The study provides another evidence on the benefit of collagen oral intake on reducing osteopenia that occurs with aging. (Wu, 2004). 

Why there are still some concerns?

In the manufacture of collagen, the heavy metal test allows levels not to exceed the approved human consumption. The effect of long collagen consumption is not completely investigated; the accumulation of heavy metals and contaminant effect would be seen after a long time, where most studies were performed for short periods.

Many other potential sources have been investigated, in Gómez-Guillén review (Gómez-Guillén, 2011). The review is considered to be a useful source for information on alternative sources.

A clear picture of the effect of collagen intake can be driven from the Japanese diet, the Japanese diet contains a large portion of collagen. But where collagen-rich diet is absent, collagen supplements are a very useful source of collagen. 

Till now collagen peptide supplement proved to be of a great benefit as long as the quality of the product is been monitored. 

References

Buehler, M. (2006). Nature designs tough collagen: explaining the nanostructure of collagen fibrils. Proceedings of the National Academy of Sciences, 103(33), 12285-12290.

Clark, K. S. (2008). 24-Week study on the use of collagen hydrolysate as a dietary supplement in athletes with activity-related joint pain. Current medical research and opinion, 25(5), 1485-1496.

Gelse, K. P. (2003). Collagens—structure, function, and biosynthesis. Advanced drug delivery, 55(12), 1531-1546.

Gómez-Guillén, M. G.-C. (2011). Functional and bioactive properties of collagen and gelatin from alternative sources: A review. Food hydrocolloids, 25(8), 1813-1827.

Lodish H, B. A. (2000). Collagen: The Fibrous Proteins of the Matrix. In B. A. Lodish H, Molecular Cell Biology. 4th edition. New York: W. H. Freeman. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK21582/

Proksch, E. S. (2014). Oral intake of specific bioactive collagen peptides reduces skin wrinkles and increases dermal matrix synthesis. Skin pharmacology and physiology, 27(3), 113-119.

Rennie, M. J. (1999). Teasing out the truth about collagen. The Journal of physiology, 521.

Wu, J. F. (2004). Assessment of effectiveness of oral administration of collagen peptide on bone metabolism in growing and mature rats. Journal of bone and mineral metabolism, 22(6), 547-553.

Zague, V. d.-S. (2011). Collagen hydrolysate intake increases skin collagen expression and suppresses matrix metalloproteinase 2 activity. Journal of medicinal food, 14(6), 618-624.