Vitamin D assessment in population-based studies: a review of the issues.
In the past decade, research on the relation between vitamin D exposure and disease in population-based studies has increased exponentially. These studies have involved measurement of vitamin D exposure by means of several methods: blood assays, self-reported dietary and supplemental intakes, and sunlight exposure questionnaires or diaries. As with all exposure measurements, researchers must consider the validity of their assessment tools for capturing vitamin D exposure. The purpose of this article is to summarize our current understanding of the various approaches to measuring vitamin D status within populations as reviewed at the 2007 Experimental Biology symposium, "Assessment of Vitamin D in Population-Based Studies." In summary, serum 25-hydroxyvitamin D is the accepted biomarker for short-term vitamin D status, but estimates of long-term dietary and supplemental intakes of vitamin D and long-term sunlight exposure may be the most logistically feasible indicators of lifetime vitamin D exposure in population-based studies. Also discussed are issues investigators should consider when analyzing relations between vitamin D exposure and disease outcomes in population-based studies as well as research avenues that need further exploration. The best method for assessing vitamin D status in population-based studies will depend primarily on the research question asked and the critical window of vitamin D exposure hypothesized to be most important.
Millen
Amy E
AE
University at Buffalo, School of Public Health and Health Professions, Department of Social and Preventive Medicine, Buffalo, NY 14214-8001, USA. aemillen@buffalo.edu
Bodnar
Lisa M
LM
D015415:Biomarkers / Q000097:blood; D050071:Bone Density Conservation Agents / Q000097:blood; D004032:Diet; D019587:Dietary Supplements; D006801:Humans; D015596:Nutrition Assessment; D009752:Nutritional Status; D013472:Sunlight; D014807:Vitamin D / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000097:blood* / Q000502:physiology; D014808:Vitamin D Deficiency / Q000175:diagnosis / Q000517:prevention & control
D015415:Biomarkers; D050071:Bone Density Conservation Agents; D014807:Vitamin D; C104450:25-hydroxyvitamin D