Development and assessment of a short instrument for assessing dietary intakes of calcium and vitamin D.

OBJECTIVE: To validate a short food frequency screening instrument designed to assess dietary intakes of calcium and vitamin D.
DESIGN: Cross-sectional surveys and food diaries. PARTICIPANTS: Twenty-seven university employees. MAIN OUTCOME MEASURES: Calcium and vitamin D intakes of participants were assessed using three instruments: a 7-day food diary, the Block-National Cancer Institute Health Habits and History Questionnaire (HHHQ), and a short screening instrument derived from the HHHQ. The accuracy of participants' reports of calcium and vitamin D intakes on the HHHQ and short screening instrument were checked against the food diaries. The validity of the full survey and the screening instrument were judged according to their correlation with the food diaries.
RESULTS: Estimates of calcium and vitamin D intakes derived from the 7-day food diary and the short screening instrument were significantly correlated (r = 0.66 and 0.72, respectively, P < .001). The mean differences between estimates derived from the short screening instrument and those derived from the 7-day food diary were 223 mg/day for calcium and 47 IU/day for vitamin D. The positive predictive value of the short screening instrument in identifying individuals with low nutrient intakes, as assessed by the 7-day food diary, was 91.7% for calcium and 100.0% for vitamin D.
CONCLUSION: The short screening instrument provides reasonably accurate estimates of calcium and vitamin D intakes. Although it cannot replace more comprehensive nutritional assessments, the screening instrument may provide quick assessments of calcium and vitamin D intakes. Given that many individuals consume suboptimal levels of these nutrients, pharmacists may use the screening instrument to evaluate patients' needs for calcium and/or vitamin D supplements and, thus, reduce their risk for developing osteoporosis.