Proposal and Validation of a Quick Question to Rate the Influence of Diet in Geriatric Epidemiological Studies on Vitamin D

Background: Diet is a major exogenous source of vitamin D. The objective of this analysis was to determine whether the yes/no answer to a simple question exploring diet (Do you eat fatty fish at least once a week and/or eggs several times per week?) could be associated with serum 25-hydroxyvitamin D status among 261 older in- and outpatients (mean +/- standard deviation, 83.5 +/- 8.1 years). Methods: Two groups were distinguished based on the binary yes/no answer. Hypovitaminosis D was defined as serum 25-hydroxyvitamin D <= 75 nmol/L. Results: More participants with hypovitaminosis D answered No to the question on diet compared to their counterparts (p = 0.002). Answering No was associated with hypovitaminosis D (OR = 3.22, p = 0.001) after adjustment for potential confounders, with a positive predictive value = 79 %. Conclusion: A simple dietary question may identify older patients with hypovitaminosis D who should receive vitamin D supplements.