Low dose ultraviolet B irradiation at 308 nm with light-emitting diode device effectively increases serum levels of 25(OH)D.

This animal study aimed to elucidate the relationship of low-dose, narrow-band UVB at 308 nm with vitamin D synthesis. C57BL/6 female mice, at 3 weeks-of-age, were randomly divided into the following six groups (n = 6 at each time point of vitamin D measurement), which were: (1) normal diet without UVB irradiation; (2) VDd diet without UVB irradiation; and (3)-(6) VDd diet with 308 nm-UVB irradiation of 12.5, 25, 50, and 100 μω/cm2, respectively. All of the groups needing UVB irradiation received an exposure of 10 min per day, five days per week, and a duration of 3-5 weeks. The mice recovering from severe VDd (plasma total 25-hydroxyvitamin D level increasing from approximately 3 to over 30 ng/mL) only occurred in groups with a UVB irradiation dosage of either 50 or 100 μω/cm2. The optimal, estimated dosage for mice to recover from severe VDd was 355 mJ/cm2 within 3 weeks. Low-dose, narrow-band UVB irradiation at 308 nm is effective in improving VDd in mice. The results obtained, in addition to the especially small side effects of the above UVB irradiation formula, could be further translated to treating VDd-related disorders.