Background: Ultraviolet (UV) radiation of human skin causes DNA damage, mainly cyclobutane pyrimidine dimers (CPDs), but also have the beneficial effect of vitamin D3 synthesis. The production of vitamin D is dependent on wavelength and can be described by weighting functions called action spectra. Current public health advice on optimal vitamin D status maintenance is partly based on the CIE pre-vitamin D actions spectrum, but this is under debate.
Aim: To simultaneously determine quantitative action spectra of vitamin D3 and CPD in human skin, obtained under identical exposure regime.
Materials and Methods: We have obtained excess waistband skin from 3 persons just after it was surgically removed. From each person’s skin tissue 82 biopsies were prepared: 80 irradiated with one of 10 UV-LEDs with wavelengths from 280 to 335 nm and 2 non-irradiated controls. Half the biopsies were quantified for vitamin D3 by UHPLC-MS/MS, the other half were quantified for CPDs in the skin by HPLC-MS/MS. For each wavelength, 4 doses with linear increments were given and a linear dose response was calculated. The regression slopes are presented as action spectra.
Results: Both vitamin D3 and CPD action spectra have the maximal peak at 290 nm with a decrease towards higher wavelengths. In the interval 295-310nm the normalized action spectra of vitamin D3 are 1.4 to 1.7 times higher than the CPD action spectra otherwise the CPD action spectra are 1.3-10 times higher. From 300 to 315 nm vitamin D3 production is relatively lower than the CIE pre-vitamin D3 action spectrum.
Conclusions: We find that that the CIE pre-vitamin D actions spectrum overestimates the vitamin D production after UVB exposure, which is in accordance with part of the literature debates.