Vitamin D insufficiency in southern Arizona

Background: Vitamin D deficiency or insufficiency has been observed among populations in the northern United States. However, data on the prevalence of vitamin D deficiency in areas of high sun exposure, such as Arizona, are limited. Objective: The purpose of this study was to analyze serum 25-hydroxyvitamin D [25(OH)D] concentrations in residents of southern Arizona and to evaluate predictors of 25(OH)D in this population. Design: Cross-sectional analyses of serum from participants in a colorectal adenoma prevention study were conducted to determine rates of vitamin D deficiency. Participants were categorized into 4 groups on the basis of serum 25(OH)D concentrations: < 10.0 ng/ mL, >= 10.0 ng/mL and < 20.0 ng/mL, >= 20.0 ng/mL and < 30.0 ng/mL, and >= 30.0 ng/mL. Results: The mean serum 25(OH)D concentration for the total population was 26.1 +/- 9.1 ng/mL. Of 637 participants, 22.3% had 25(OH)D concentrations > 30 ng/mL, 25.4% had concentrations < 20 ng/mL, and 2.0% had concentrations < 10 ng/mL. Blacks (55.5%) and Hispanics (37.6%) were more likely to have deficient 25(OH)D concentrations (< 20 ng/mL) than were non-Hispanic whites (22.7%). Sun exposure had a greater effect on 25(OH)D in whites than in blacks and Hispanics, whereas BMI appeared to be more important in the latter groups. Conclusion: Despite residing in a region with high chronic sun exposure, adults in southern Arizona are commonly deficient in vitamin D deficiency, particularly blacks and Hispanics.