Validation of a New Food Frequency Questionnaire for Assessment of Calcium and Vitamin D Intake in Korean Women

BACKGROUND Validated simple calcium questionnaires are available to assess the intake of calcium and vitamin D in western countries, but they are not appropriate for Koreans since dairy products are not the major source of calcium and vitamin D in Korea. Thus, the objective of the present study was to develop and validate a simple and easy food frequency questionnaire (FFQ) of calcium and vitamin D for Korean. METHODS Two hundred and fifty-six women were asked to complete the validated FFQ used by the Korean National Health and Nutrition Examination Survey (KNHANES) and a newly developed FFQ, the Korean Calcium Assessment Tool (KCAT), which contain the 7 food groups with 24 categories of 45 food items that are consumed frequently by Koreans. RESULTS Calcium intake was not significantly different between the two methods; Pearson's correlation coefficient of 0.98 indicated a positive correlation, and Cohen's kappa coefficient of 0.78 indicated the subjects were correctly classified. Bland-Altman plot also showed that the mean differences of the calcium intake as assessed by the two methods were in high agreement. However, the vitamin D intake assessed by KCAT was significantly higher than that assessed by the FFQ used in KNHANES. The vitamin D intakes as assessed by the two methods were positively correlated but the two methods were in moderate agreement. CONCLUSIONS The results suggested that the newly developed KCAT was a valid tool for assessing the calcium intake in Korean women, but it might overestimate the vitamin D intake.