Relative Validity and Repeatability of a Zinc-FFQ for Estimating Intakes of Iron, Copper and Selenium in Saudi Adults

Background: In Saudi Arabia, few studies have addressed iron, selenium and copper intake and status. Most studies on iron have focused on iron deficiency anemia rather than the intake of iron. Objective: To assess the relative validity and repeatability of a Zinc-food Frequency Questionnaire (FFQ) for estimating the intakes of iron, copper and selenium in Saudi adults. Methods: Ninety-seven Saudi adults participated in this study. All participants completed the FFQ1 and a three-days (3d) Food Record (FR) to assess validity. After one month, the FFQ was administered again (FFQ2) to assess the repeatability. Results: Mean intakes of iron, copper and selenium estimated by FFQ1 were significantly higher than those from the 3d FR. Estimated intakes of iron and selenium by both methods were significantly correlated. The Bland-Altman analysis showed that the difference in iron intakes, as measured by the two methods, was similar across the range of intakes while the difference in copper and selenium intakes increased with an increase in the mean intake. No detectable differences were observed between FFQ1 and FFQ2 in estimating iron, copper and selenium intakes. For all nutrients, the intakes from both FFQs were highly correlated. Conclusion: The Zinc-FFQ showed reasonable relative validity and repeatability for estimating other micronutrients, such as iron, copper and selenium.