Vitamin D Assessment Using Simple Questionnaires from a College Cohort Study

Abstract

Vitamin D is important to the health of college students. Our objective was to measure vitamin D intake, sun exposure, skin pigmentation, and serum 25‐hydroxyvitamin D (25[OH]D) in a subset of students from the FLASH Longitudinal College Health Study at Cal Poly, San Luis Obispo, CA. Vitamin D intake and sun exposure were measured using two different tools. First, an online categorical (C) questionnaire administered by the FLASH Study including fish and milk intake, minutes in the sun on the weekdays and weekends. Second, a 28 day recall (R) questionnaire specific to vitamin D foods/supplements, and sun exposure with minutes outside and clothing worn to calculate a sun exposure index (SEI). Skin pigmentation was measured using a reflectance spectrophotometer. Serum 25(OH)D was measured at a local pathology lab. The different measurements for diet and sun exposure were each incorporated into a regression model along with average forehead skin reflectance (FSR) to predict 25(OH)D (Spring 2010, n=35). The average SEI from 11am–3pm (R), fish intake (C), and FSR were significant predictors (R2=0.39, p=0.0036). Weekend sun exposure (C), average monthly intake of vitamin D (R) and FSR were also significant predictors (R2=0.42, p=0.0005). Weekend sun exposure (C), fish intake (C), and FSR were the strongest predictors (R2=0.50, p=0.0001). Thus, simple questionnaires can be used to help determine vitamin D status.