Vitamin B12 and Sunlight: Good or Bad Idea?

Some molecules used in cosmetic formulation, such as vitamin A or AHAs, do not interact well with sunlight. By increasing the skin's sensitivity to UV rays, they can exacerbate the skin risks associated with sun exposure (sunburn, dehydration...). Depending on the molecules, the mechanisms involved vary slightly, involving or not reactive oxygen species (ROS), produced in excess in situations of oxidative stress. Generally, a photosensitising substance reacts under the effect of the sun to transform into a molecule deteriorating the skin structures and weakening the epidermal barrier, making the skin more sensitive.

Vitamin B12 is compatible with sun exposure.

Also known as cobalamin, vitamin B12 is a cosmetic active ingredient that can be incorporated into various formulations. It has an interesting feature, derived from its chemical structure, presented below, and its central cobalt atom: it gives cosmetics a slight pink color. The structure of vitamin B12 is also partly responsible for its photoprotective character. Indeed, thanks to its double bonds, this compound can stabilize free radicals and thus reduce oxidative stress in skin cells. Moreover, in vitro studies have demonstrated the ability of vitamin B12 to activate glutathione, which plays a role in maintaining the redox potential of cells. This active ingredient thus protects the skin from photoaging, a phenomenon that manifests as premature sagging of skin structures and the appearance of sun spots.

Following sun exposure, the skin requires cooling and the restoration of its weakened protective barrier. Indeed, the sun tends to destabilise the skin's water balance and disorganise the stratum corneum, which increases water loss. Moreover, UV rays stimulate the skin's inflammatory mechanisms. The free radicals they produce can activate certain nuclear factors such as the AP-1 transcription factor, involved in the release of cytokines, molecules that promote erythema and oedema.

The vitamin B12 can soothe inflammations caused by sun exposure by reducing the release of pro-inflammatory cytokines. Furthermore, it has an inhibitory effect on the synthesis of nitric oxide (NO), a vasodilating compound. Indeed, NO stimulates the production of cyclic guanosine monophosphate (cGMP), a nucleotide that leads to a reduction in the tone of smooth muscles and an increase in the diameter of blood vessels, which promotes the redness and swelling observed after sun exposure. It should be noted that the anti-inflammatory properties of vitamin B12, first observed in vitro, were subsequently demonstrated in clinical trials.

The key takeaway : Combining vitamin B12 and sunlight is a good idea, due to the antioxidant and soothing properties of this active ingredient.