Combining a Food Frequency Questionnaire With 24-Hour Recalls to Increase the Precision of Estimating Usual Dietary Intakes – Evidence From the Validation Studies Pooling Project

Abstract

Improving estimates of individuals' dietary intakes is key to obtaining more reliable evidence for diet-health relationships from nutritional cohort studies. One approach to improvement is combining information from different self-report instruments. Previous work evaluated the gains obtained from combining information from a food frequency questionnaire (FFQ) and multiple 24-hour recalls (24HRs), based on assuming that 24HRs provide unbiased measures of individual intakes. Here, we evaluate the same approach of combining instruments, but based on the better assumption that recovery biomarkers provide unbiased measures of individual intakes. Our analysis uses data from the five large validation studies included in the Validation Studies Pooling Project: the Observing Protein and Energy study (1999–2000), Automated Multiple Pass Method validation study (2002–4), Energetics study (2006–9), Nutrition Biomarker Study (2004–5) and Nutrition and Physical Activity Assessment Study (2007–9). The data include intakes of energy, protein, potassium, and sodium. Under a time-varying usual intake model analysis, combining a FFQ with 4 24HRs improved correlations with true intake for predicted intakes of protein density, potassium density and sodium density (range 0.39–0.61), over a single FFQ (range 0.35–0.51). Absolute increases in correlation ranged from 0.02 to 0.26, depending on nutrient and sex, with an average increase of 0.14. Based on unbiased recovery biomarker evaluation for these nutrients, we confirm that combining a FFQ with multiple 24HRs modestly improves the accuracy of estimates of individual intakes.