(05-10-11) Solar UV Doses of Young Americans and Vitamin D3 Production.

Godar DE, Pope SJ, Grant WB, Holick MF.
Source
Food and Drug Administration.
Abstract
Background: Sunlight contains UVB radiation (290-315 nm) that affects human health in both detrimental (skin cancers) and beneficial (vitamin D3) ways. Serum 25-hydroxyvitamin D concentrations of young Americans (??19 yr) show many have deficient (<50 nmol/L, 20 ng/ml) or insufficient (<75 nmol/L, 30 ng/ml) vitamin D levels, indicating they are not getting enough sun exposure. Those findings are in conflict with some calculated, published values that suggest people make "ample" vitamin D3 (~1,000 IU/day) from their "casual," or everyday, outdoor exposures even if they diligently use sunscreens with sun protection factor 15. Objective: We estimated how much vitamin D3 young Americans (~2,000) produce from their everyday outdoor UV doses in the north (45??N) and south (35??N) each season of the year with and without vacationing. Methods: To do these vitamin D3 calculations properly, 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 D3 needs all year, except some Caucasians during the summer if they do not diligently wear sunscreens except during beach vacations. Conclusion: These estimates suggest 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.

Source: Environ Health Perspect. 2011 Aug 18.

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