Collagen: the benefits for hair.

Collagen is a protein naturally found in the body. Synthesised by fibroblasts, it provides mechanical resistance to stretching and structure to many connective tissues. This is why collagen is present in the skin, muscles, bones, ligaments, tendons, and even hair. This active ingredient is also found in cosmetic formulations, where it is particularly used to create hair care products.

To date, there are no clinical trials on the benefits of collagen in hair applications.

It can nevertheless be assumed that collagen could provide hydration to the hair. Indeed, it has been shown that this compound forms a film on the skin, allowing it to be protected and to limit insensible water loss. A similar mechanism can be assumed on hair fibres, where collagen could act in support of the hydrolipidic film, synthesized at the scalp level and enveloping the hair.

Furthermore, some researchers have shown that collagen possesses anti-radical properties and can protect skin cells. It is possible that this antioxidant activity also occurs at the level of hair follicles, which are located at the root of the hair and are sensitive to attacks from free radicals. The repeated action of these unstable molecules can disrupt the process of melanogenesis and accelerate the appearance of grey hair. Additionally, free radicals can interfere with the hair cycle and precipitate hair loss. It can thus be hypothesised that collagen could potentially help prevent these issues and protect the scalp and hair fibres.

Better documented but also more controversial, collagen supplementation could help in hair care. A double-blind study conducted over 52 weeks with 54 participants divided into two groups (an "active substance" group and a "placebo" group) examined the effects of daily collagen intake. The results of this study are presented in the following table and seem to show hydrating effects of collagen, although the underlying mechanism has not been specified.

Furthermore, other studies conducted ex vivo and in vivo in mice reveal that collagen could stimulate hair growth. Indeed, it appears that this active ingredient can prolong the growth phase of the hair follicle, also known as the anagen phase, by inducing the expression of Ki67, a growth factor for hair fibres. This property was later demonstrated in a clinical trial where collagen and amino acid supplementation allowed individuals suffering from alopecia to see their hair density increase.

However, this is only a single study. More scientific evidence is needed to assert that collagen-based dietary supplements can stimulate hair growth.

Finally, another study suggests that collagen supplementation could increase the thickness of hair fibres. Conducted over 16 weeks, this study involved 44 women who took 2.5 g of collagen peptides or a placebo daily. An increase of 1.93 ± 0.42 μm in the hair diameter of the volunteers who received collagen was measured, while a non-significant decrease was observed in the placebo group. It would be interesting for this effect of collagen to be investigated in further clinical trials, incorporating a larger number of participants.

• GANS E. H. & al. A Nutritional Supplement Formulated with Peptides, Lipids, Collagen and Hyaluronic Acid Optimizes Key Aspects of Physical Appearance in Nails, Hair and Skin. Journal of Nutrition and Food Sciences (2014).

• OESSER S. The oral intake of specific Bioactive Collagen Peptides has a positive effect on hair thickness. Nutrafoods (2020).

• LEE B. H. & al. Hair-Growth-Promoting Effects of the Fish Collagen Peptide in Human Dermal Papilla Cells and C57BL/6 Mice Modulating Wnt/β-Catenin and BMP Signaling Pathways. International Journal of Molecular Sciences (2022).

• FIORUCCI M. & al. Efficacy and tolerability of an oral supplement containing amino acids, iron, selenium, and marine hydrolyzed collagen in subjects with hair loss (androgenetic alopecia, AGA or FAGA or telogen effluvium). A prospective, randomized, 3-month, controlled, assessor-blinded study. Skin Research and Technology (2023).