U.S. Food and Drug Administration, Center for Devices and Radiological Health, 10903 New Hampshire Ave., Silver Spring, MD 20993-0002, USA.
Environ Health Perspect. 2012 Jan;120(1):139-43. doi: 10.1289/ehp.1003195. Epub 2011 Aug 18.
Sunlight contains ultraviolet B (UVB) radiation (290-315 nm) that affects human health in both detrimental (skin cancers) and beneficial (vitamin D3) 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 D3 (~ 1,000 IU/day) from their "casual," or everyday, outdoor exposures even if they diligently use sunscreens with sun protection factor (SPF) 15.
We estimated how much vitamin D3 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.
For these vitamin D3 calculations, we used geometric conversion factors that change planar to whole-body doses, which previous calculations did not incorporate.
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.
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.
阳光包含紫外线 B（UVB）辐射（290-315nm），对人类健康既有不利影响（皮肤癌）也有有益影响（维生素 D3）。年轻美国人（≤ 19 岁）的血清 25-羟基维生素 D 浓度表明，许多人维生素 D 水平不足（<50nmol/L，20ng/mL）或不足（<75nmol/L，30ng/mL），这表明他们没有得到足够的阳光照射。这些发现与一些计算出来的、已发表的数值相矛盾，这些数值表明，即使人们每天勤奋地使用防晒系数（SPF）为 15 的防晒霜，他们也可以从日常户外活动中获得足够的维生素 D3（~1000IU/天），即使他们每天都在户外活动，即使他们每天都在户外活动。
我们估计了年轻的美国人（n = ~2000）在每年的北（45°N）和南（35°N）每个季节，在没有度假和有度假的情况下，从日常户外活动中的紫外线剂量中产生了多少维生素 D3。
对于这些维生素 D3 的计算，我们使用了几何转换因子，将平面剂量转换为全身剂量，而之前的计算并没有包含这些因子。
我们的估计表明，除非一些高加索人在夏天不戴防晒霜，只在海滩度假时戴防晒霜，否则美国儿童可能全年都无法获得足够的户外 UVB 暴露来满足他们的维生素 D3 需求。
这些估计表明，大多数美国儿童可能没有足够的户外活动来满足他们的最低（~600IU/天）或最佳（≥1200IU/天）维生素 D 需求。
