Vitamin C May Help Slow Thinning Skin With Age

Vitamin C, a nutrient abundant in fresh fruit and vegetables, may help slow a visible aspect of ageing: thinning skin.

New research has shown that supplying vitamin C to laboratory-grown models of human skin increases epidermal thickness by switching genes associated with cell growth back on. Importantly, the levels of vitamin C that normally reach skin through the bloodstream appear sufficient to produce a measurable result.

Research led by pharmaceutical scientist Yasunori Sato of Hokuriku University in Japan suggests that vitamin C could help ward off at least some of ageing’s effects on the body’s largest organ.

Vitamin C and thinning skin

"Vitamin C seems to influence the structure and function of epidermis, especially by controlling the growth of epidermal cells," explains biologist Akihito Ishigami of the Tokyo Metropolitan Institute for Geriatrics and Gerontology.

"We investigated whether it promotes cell proliferation and differentiation via epigenetic changes."

Healthy human skin contains substantial levels of vitamin C, indicating that it is actively accumulated. Levels are lower, however, in skin affected by age or UV damage. The vitamin is already known to support skin health by increasing collagen production, reducing UV damage and offering antioxidant protection.

Vitamin C is also involved in DNA demethylation, the removal of methyl groups – a process important for genetic stability and gene expression.

Adding or removing methyl groups works rather like a molecular switch, enabling gene activity to be turned on or off without altering the genomic sequence.

Until now, though, the part played by demethylation in the differentiation of keratinocytes – skin cells – had not been clear.

How vitamin C affects the epidermis

Keratinocytes make up most of the human epidermis. They are formed in its lowest layer, then gradually travel upwards through the skin’s several layers as they mature. Eventually, they become the dead cells of the uppermost skin layer, the stratum corneum.

Made entirely of dead cells, the stratum corneum protects the living skin cells below. Dead cells are shed from this layer and replaced by keratinocytes moving upwards from beneath.

To examine vitamin C’s part in skin health, the team cultured human keratinocytes in Petri dishes. Their upper surface was exposed to air while a nutrient solution fed them from below, replicating the behaviour of skin in living people.

The scientists added vitamin C to the nutrient solution at concentrations matching those supplied by the circulatory system. They also cultured a separate set of cells without vitamin C as a control.

After one week, the vitamin C-fed models had a thicker layer of living epidermal cells than the control models, although the stratum corneum was unaffected. By day 14, the epidermal cell layer had thickened further and the stratum corneum had become thinner, indicating that vitamin C was encouraging cell proliferation.

DNA demethylation and cell growth

The researchers sequenced DNA and RNA from the samples, linking the growth in cell numbers to demethylation apparently driven by vitamin C maintaining the activity of enzymes that control gene activity.

These enzymes require a particular form of iron to continue their demethylation work, and vitamin C helps restore that iron form. In turn, this reactivates genes connected with cell proliferation.

In samples exposed to vitamin C, expression of 12 important proliferation genes increased, with some rising by as much as 75 times.

When the researchers used an inhibitor against the enzyme, the effect was reversed, confirming that vitamin C acts through this particular route. The findings indicate that the vitamin could be useful in developing treatments to counter the effects of age.

"We found that vitamin C helps thicken the skin by encouraging keratinocyte proliferation through DNA demethylation," Ishigami says, "making it a promising treatment for thinning skin, especially in older adults."

The study was published in the Journal of Investigative Dermatology.