What are the benefits of resveratrol for the skin?

In normal and non-stressed cells, there is a constant production of reactive oxygen and nitrogen species at the mitochondrial level, which is balanced by the combined operation of non-enzymatic bioactive substances (vitamins C and E, β-carotene, lycopene, etc.) and antioxidant enzymes (Zn/Cu and Mn superoxide dismutase, glutathione peroxidases and catalase). However, when a cell is subjected to stress, this balance is disrupted and reactive oxygen species accumulate, leading to a change in cell behaviour.

The skin, which is constantly exposed to pro-oxidant internal and external influences from various sources (atmospheric pollutants, sunlight, chemical oxidants, stress, etc.), can experience alterations in its condition and physiological functioning. The free radicals produced in large quantities then cause skin damage, ranging from brown spots to premature ageing and inflammation.

However, it has been demonstrated that resveratrol possesses an inherent antioxidant capacity, with both preventive and therapeutic effects, by modulating the oxidative imbalances that occur during chronic ageing. Indeed, it is capable of neutralising free radicals and inducing the expression of a number of antioxidant enzymes so that the skin can better defend and repair itself.

It has been observed that resveratrol acts as a superior free radical scavenger compared to vitamins C and E.

Resveratrol also forms complex molecules with certain metallic ions, neutralising their ability to form free radicals, which enhances cellular function and supports fibroblasts, as well as the creation of healthy collagen. Other studies in vitro have shown that resveratrol also protects human fibroblasts from the harmful effects of hydrogen peroxide.

This combination of data highlights that resveratrol is effective in the battle against the harmful effects of free radicals.

Resveratrol would interfere with inflammation by regulating numerous intracellular signalling cascades that converge towards the activation of NF-kB. These pathways act independently or in combination to control the expression of target genes, such as TNF-α, IL-1β and metalloproteinases.

In vivo experiments on mice have demonstrated a reduction in TNF-α in splenic cells following a 2 to 4 week resveratrol treatment, thereby blocking the early stage of the inflammatory process.

Similarly, a study demonstrated the ability of a combination of antioxidants (resveratrol, green tea polyphenols and caffeine) to reduce facial redness in 13 out of 16 subjects (81%) after 6 weeks of application (twice daily). Conditions such as eczema and psoriasis also showed improvement with the use of resveratrol, according to a 2020 study.

Hyperkeratosis, characterised by a significant increase in keratinisation, is at the root of certain dermatological conditions (ichthyosis, psoriasis, acne, keratosis pilaris, etc.). However, a study in vitro has revealed that resveratrol is capable of modulating the proliferation of normal human keratinocytes even at concentrations as low as 0.25 mM of resveratrol. On the other hand, at higher concentrations (40 - 100 mmol/L), it is cytotoxic to these cells.

Another study on HaCaT cells, which are immortalised human keratinocytes, indicated the ability of resveratrol to induce the phosphorylation of the adaptive protein p66Shc to mediate a slowdown in proliferation and cellular function in the outer layer of the skin. At high doses, it leads to apoptosis, whereas under physiological conditions, it promotes senescence, that is, a slowdown in cell activity.

Resveratrol would therefore be beneficial in the treatment of skin diseases, such as acne and psoriasis.

Several studies have highlighted thebactericidal effect of resveratrol at various concentrations on several bacteria, particularly Neisseria gonorrhoeae, Neisseria meningitidis, Helicobacter pylori, Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa and Proteus mirabilis.

A study has even evaluated the capacity and effectiveness of resveratrol, at concentrations ranging from 0 to 200 mg/L, on three different strains of Propionibacterium acnes, an anaerobic bacterium that plays a role in the pathogenesis of acne. After 24 hours of treatment, the results showed that resveratrol was able to inhibit the replication of P. acnes.

In a randomised double-blind study, 30 patients were treated daily for ten weeks with a topical cream containing 1% resveratrol. A significant reduction in the number of inflammatory lesions and comedones was observed in 95% of the treated patients compared to the control subject (2%).

In 2011, the clinical evaluation of a single-blind, vehicle-controlled pilot study on 20 patients suffering from vulgar acne also demonstrated a 66.7% decrease in the density of acne lesions on the side of the face treated with a gel containing resveratrol (0.01%) for 60 days, compared to a decrease of 9.7% on the side of the face treated with the vehicle.

Resveratrol could therefore represent a potentially interesting molecule in the treatment of acne due to its ability to inhibit the proliferation of keratinocytes and the replication of P. acnes, as well as its anti-inflammatory properties.

Beyond topical application, another method of delivering resveratrol to the skin is through oral administration via diet and dietary supplements.

A small study from 2012 reported the moisturising effects of resveratrol following oral administration of dietary supplements. Compared to the placebo group (n = 25), the 25 subjects treated with dietary supplements characterised by a blend of resveratrol (8 mg), procyanidins (14.63 mg) and other phytochemical compounds (ellagic acid, anthocyanosides, flavonoids, etc.) saw their skin hydration levels improve after 60 days of treatment, associated with a decrease in wrinkle depth. Further studies are needed to better understand the mechanism by which resveratrol is able to hydrate the skin.

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