Sun exposure and 25-hydroxyvitamin D 3 levels in a community sample: Quantifying the association with electronic dosimeters

There is uncertainty about the amount of sun exposure required to increase low blood 25-hydroxyvitamin d (25(oh)d3) levels, a possible disease risk factor. the study aimed to quantify the association between sun exposure and serum 25(oh)d3 concentrations in a multiethnic community sample (n=502) living in auckland (37°s) and dunedin (46°s), new zealand, aged 18–85 years. they wore electronic ultraviolet dosimeters between march and november (autumn, winter and spring) for 8 weeks to record their sun exposure. this was converted to standard erythemal doses (seds), corrected for clothing to generate equivalent full-body exposures, sedefb. blood samples were collected at the end of weeks 4 and 8 to measure 25(oh)d3. median weekly sedefb was 0.33 during weeks 1–4 and 0.34 during weeks 5–8. weekly exposures <0.5 sedefb during weeks 5–8 were associated with decreasing 25(oh)d3 concentrations at the end of week 8. there was a non-linear association between sun exposure and 25(oh)d3, with most of the increase in 25(oh)d3 being at exposures <2 sedefb per week. this finding suggests that vitamin d status is increased by regular small sun exposures (<2 sedefb per week), and that greater exposures result in only small additional increases in 25(oh)d3.