Solar UV doses of young Americans and vitamin D 3 production

摘要

Background: Sunlight contains ultraviolet B (UVB) radiation (290-315 nm) that affects human health in both detrimental (skin cancers) and beneficial (vitamin D 3) ways. Serum 25-hydroxyvitamin D concentrations from young Americans (≤ 19 years) show that many have deficient ( 50 nmol/L, 20 ng/mL) or insufficient ( 75 nmol/L, 30 ng/mL) vitamin D levels, indicating that they are not getting enough sun exposure. Those findings are in conflict with some calculated, published values that suggest people make "ample" vitamin D 3 (~ 1,000 IU/day) from their "casual," or everyday, outdoor exposures even if they diligently use sunscreens with sun protection factor (SPF) 15. Objective: We estimated how much vitamin D 3 young Americans (n = ~ 2,000) produce from their everyday outdoor ultraviolet doses in the North (45°N) and South (35°N) each season of the year with and without vacationing. Methods: For these vitamin D 3 calculations, we used geometric conversion factors that change planar to whole-body doses, which previous calculations did not incorporate. Results: Our estimates suggest that American children may not be getting adequate outdoor UVB exposures to satisfy their vitamin D 3 needs all year, except some Caucasians during the summer if they do not diligently wear sunscreens except during beach vacations. Conclusion: These estimates suggest that most American children may not be going outside enough to meet their minimal (~ 600 IU/day) or optimal (≥ 1,200 IU/day) vitamin D requirements.