Vitamin D and ultraviolet radiation exposure – a photodermatologist’s viewpoint

Vitamin D is essential for bone health and possibly various other health outcomes. It is available following ultraviolet (UV)-B (280-315nm) irradiation of skin, or oral ingestion. Careful sunscreen use of sun protection factors (SPFs) 18-19 during such exposure reduces blood level increases on sunny holidays by up to about 50%, but these increases remain significant. Further, the maintenance of such levels requires unprotected exposures of only a fraction of the sunburn dose over small body areas. Finally, skin colour, whether fair or dark, has no effect on these levels. Unprotected UVB exposure induces potentially precancerous skin thymine dimers and is not advocated to maintain vitamin D status, but rather protected exposure or else oral supplementation. Minimal skin UVB exposure seems an innate requirement for not only vitamin D production, but also contact dermatitis and polymorphic light eruption avoidance, and anti-bacterial defensin induction.