Narrowband ultraviolet B course improves vitamin D balance in women in winter

Summary Background Vitamin D insufficiency is common in winter in the Nordic countries. Objectives To examine whether a short course of narrowband ultraviolet B (NB‐UVB) improves vitamin D balance. Methods Fifty‐six healthy, white women (mean age 41 years) volunteered and 53 completed the study. NB‐UVB exposures were given on seven consecutive days either on the whole body (n = 19), on the head and arms (n = 9) or on the abdomen (n = 14). Similarly, seven solar simulator exposures were given on the face and arms (n = 11). The cumulative UVB dose was 13 standard erythema doses in all regimens. Serum calcidiol (25‐hydroxyvitamin D) concentration was measured by radioimmunoassay before and after the NB‐UVB exposures. Follow‐up samples were taken from the whole‐body NB‐UVB group at 2 months. Results At onset 41 women (77%) had vitamin D insufficiency (calcidiol