Themed collection Vitamin D update

The editors introduce the collection of papers updating several issues of vitamin D and health.

Vitamin D is made in the skin under the same wavelength of light (UVB) that induces skin cancer. Evidence that vitamin D production may counter the carcinogenic effects of UVB in the skin is reviewed.

There are only a few natural foods that contain nutritionally significant quantities of vitamin D.

Clinical pharmacologists at Karolinska Institutet describe that seasonal changes in sunlight and vitamin D have an impact on the enzymes that are responsible for detoxification reactions, and that this contributes to variable exposure to therapeutic drugs.

Here we discuss the converging and diverging immunoregulatory pathways of ultraviolet radiation and vitamin D, and potential in vivo approaches to determine if vitamin D mediates the immunosuppressive effects of UVR.

The solar irradiances for the initiation of vitamin D synthesis (UV_D3) have been measured concurrently with the amount of cloud cover to investigate the influence of high cloud cover fraction.

A mid-winter 8-week sub-erythemal tanning course raised vitamin D levels to high summer levels, as did an 8-week course of vitamin D supplementation @ 1000 IU per day. But neither lowered the incidence of colds significantly.

Photoprotection by 1,25(OH)₂D₃ against UV-induced cyclobutane pyrimidine dimers, 8-oxo-7,8-dihydro-2′-deoxyguanosine and abasic sites in skin is demonstrated by comet assay with site specific DNA repair enzymes and by immunohistochemistry. Possible mechanisms for these protective effects are discussed.

We found that patients with polymorphic light eruption have low serum 25-hydroxyvitamin-D₃ levels. 311 nm UVB phototherapy increased those levels. This boosting of vitamin D levels may be important in ameliorating polymorphic light eruption.

Here we show that a low-calcaemic vitamin D analogue, QW, is photoprotective in vitro and in vivo. Like the active vitamin D hormone, 1,25-dihydroxyvitamin D3, QW protects against ultraviolet radiation-induced cell loss, DNA damage and immunosuppression.

Solar-UVR exposure of hands and face did not increase 25(OH)D significantly and was less effective in increasing 25(OH)D compared to artificial UVB by a factor of at least 8.