Quantifying UV exposure, vitamin D status and their relationship in a group of high school students in an alpine environment

The relationship between personal UV exposure and vitamin D status was studied among 7 high school students from Davos, Switzerland from March to August 2013. The personal UV exposure was monitored using electronic dosimeters, while blood samples were taken at monthly intervals to determine the serum concentration of 25-hydroxyvitamin D3 (25(OH)D3). During school days students were exposed to 1.7% of the ambient UV irradiance, while 85% of the cumulative UV dose was obtained on weekends and holidays. Insufficient vitamin D levels in March (9 ng ml(-1) 25(OH)D3) rose to 25(OH)D3 concentrations of over 40 ng ml(-1), meeting sufficient levels in August. The increase in vitamin D levels among 5 high school students correlated well (r = 0.89) with their measured personal UV exposure, yielding a mean increase in serum 25(OH)D3 concentration of 0.38 ± 0.22 ng ml(-1) per 100 J m(-2) of vitamin D-weighted UV exposure, a value consistent with other studies. During certain periods of the study, increases in vitamin D status and UV doses differed from the average of the whole study, implying that other factors must influence vitamin D metabolism.