Vitamin D serves as a keratinization regulator, which helps to enhance skin feel and firmness over time. It may have antioxidant and skin-soothing properties, among other benefits. According to research, vitamin D plays a significant role in epidermal cell turnover. It is commonly found in conjunction with vitamin A, and this combination tends to aid epithelial development and promote healthy skin pigmentation.

See also:
Vitamin A
UVA
UVB