ORIGINAL PAPER Prevalence of Vitamin D 3 Deficiency in Orange County Residents Moiz Horani • Azriel Dror • Dustin Holland • Fred Caporaso • Ken D. Sumida • Frank Frisch Published online: 13 February 2011 Ó Springer Science+Business Media, LLC 2011 Abstract With the prevalence of sunlight exposure in Orange County, California, one would expect it to be rare and unusual to find high incidence of Vitamin D defi- ciencies among its residents. This study evaluated the concentration of Vitamin D3 as part of a larger study to evaluate bone health in Orange County residents. Our preliminary data shows that 19.2% of the 151 subjects evaluated had low Vitamin D3 ( \ 30 pg/ml) and illumi- nates a growing problem in the United States. We speculate that the widespread sensitivity to skin cancer and sun exposure, the increased use of sun-screens and the filtering of UV waves in automobile glass has put the public at risk for low Vitamin D. Keywords Vitamin D Á Osteoporosis Á Orange County Á Bone health Introduction Physicians throughout Orange County, California are reporting an increase in Vitamin D 3 deficiencies. With an escalating number of Vitamin D 3 deficient patients, there is a growing need for research that provides a more definite and responsible survey of Orange County residents. We already know of several sources that can lead to Vitamin D 3 deficiency including inadequate sun exposure, dietary malabsorption, abnormal metabolism, and resistance to Vitamin D 3 . Vitamin D 3 deficiency is a key player in the onset of several diseases including rickets, osteomalacia, and possibly osteoporosis. Since Vitamin D 3 is a critical hormone in calcium (Ca) and bone metabolism, the reasons behind Vitamin D 3 defi- ciencies may also be factors in the increasing rate of low bone mineral densities (BMD) in the same populations. The following article is a communication on the findings of our study to test whether on the low Vitamin D levels among Orange County residents is significant despite the significant amount of sunshine that is received in South- ern California and the significant amount of Vitamin D fortified foods that are readily available. Furthermore, the impact of Vitamin D 3 on bone health and the corre- sponding predicament facing Orange County resident is discussed. Vitamin D 3 Synthesis Vitamin D 3 is a secosteroid prohormone that is transported throughout the body by Vitamin D 3 binding protein [1]. Although dietary Vitamin D 3 can be beneficial in cases of severe deficiency, the majority of Vitamin D 3 intake requires exposure to sunlight’s ultraviolet (UV-B, 290–315 nm) radiation, which is plentiful in Southern California with a mean of 186 clear days per year [2, 3]. In the plasma of certain epidermal cells, 7-dehydrocho- lesterol absorbs UVB radiation and is converted to cho- lecalciferol. Cholecalciferol (inactive Vitamin D 3 ) is transported to the liver, where it is converted to 25-hydroxycholecalciferol [25(OH)D or calcidiol] [4]. Calcidiol is the main circulating Vitamin D 3 metabolite M. Horani Á A. Dror Á D. Holland Á K. D. Sumida Á F. Frisch (&) Department of Biological Sciences, Chapman University, Orange, CA 92866, USA e-mail: frisch@chapman.edu F. Caporaso Department of Food Science, Chapman University, Orange, CA 92866, USA 123 J Community Health (2011) 36:760–764 DOI 10.1007/s10900-011-9372-8