Evaluation of Methods to Determine Usual Ultra-Processed Food Intake Using 24-Hour Dietary Recalls

Abstract

Ultra-processed foods (UPF), defined by their extensive industrial processing and poor nutritional quality, likely pose significant health risks and dominate modern diets. Reducing UPF consumption could lead to better health outcomes. Definitions of food processing levels in classification systems such as Nova are somewhat subjective, which could lead to inconsistencies in categorizing foods. Food misclassification could impact research findings on the relationship between processed food consumption and health. This study's objective was to evaluate an approach to determine usual UPF intake using 24-hour dietary recalls and Nutrition Data System for Research (NDSR) software. Dietary data was utilized from participants in two ongoing randomized controlled trials of UPF intake and health. Participants (n=47) completed three 24-hour recalls obtained using recommended procedures. Two raters independently categorized each food consumed according to the Nova system, consistent with published "best practices". Using dietary data for each 24-h dietary recall, we calculated each participant's intake of the four Nova groups: 1) minimally processed foods, 2) processed culinary ingredients, 3) processed foods, and 4) ultra-processed foods. The relative contribution to daily energy intake (percentage of total energy) and daily food intake in grams (% of total grams) were calculated. Inter-rater reliability for Nova classifications of foods was determined using Intra-Class Correlations (ICC). A paired sample t-test was used to evaluate the % UPF kcal and % UPF grams calculations between raters. The findings suggest that the Nova classification system can be applied with reasonable consistency by trained raters and may be a useful tool for estimating usual UPF intake in research settings. However, variability in dietary recall detail and food descriptions highlights the importance of using standardized classification procedures to ensure reliability in UPF-related dietary assessments. Continued refinement of these methods will be essential for improving accuracy in dietary research and informing public health strategies aimed at reducing UPF consumption.