Description and performance evaluation of two diet quality scores based on the Nova classification system

Background and objectivesThe consumption of unprocessed or minimally processed whole plant foods and of ultra-processed foods, as defined by the Nova food classification system, are associated in opposite ways with diet quality and risk of diseases. However, it can be difficult to evaluate and monitor the consumption of these foods in some contexts due to lack of resources and time constraints for data collection. This study aimed to describe two simple and easily derived diet quality scores and evaluate their performance in reflecting the dietary share of unprocessed or minimally processed whole plant foods and ultra-processed foods. MethodsA total of 812 adults (18 years old or older) answered the Nova24h screener, a 2-minute self-administered questionnaire that measures the consumption of a set of foods on the day before the interview. Food items included in this tool belong to two main groups of Nova classification: unprocessed or minimally processed whole plant foods (WPF, 33 food items) and ultra-processed foods (UPF, 23 food items). Two scores are obtained from this tool by summing the number of items checked - the Nova-WPF and the Nova-UPF. We compared the Nova-WPF and the Nova-UPF scores with the dietary intake (% of total energy) of all unprocessed or minimally processed whole plant foods and all ultra-processed foods, respectively, obtained through a full self-administered web-based 24-hour recall, applied on the same day. We evaluated the relationship between the approximate quintiles or intervals of each score and the corresponding % of energy intake by linear regression, and the agreement between the intervals of each score with the intervals of the corresponding % of energy intake, using the Prevalence-Adjusted and Bias-Adjusted Kappa (PABAK). ResultsApproximate quintiles of each score presented a direct and linear relationship with the corresponding % of energy intake (p-value for linear trend <0.001). We found a substantial agreement between the intervals of each score and of the corresponding % of energy intake (PABAK 0.72, 95% CI 0.64-0.81 for the Nova-WPF score and PABAK 0.79, 95% CI 0.69-0.88, for the Nova-UPF score). ConclusionsThese two scores performed well against the dietary share of unprocessed or minimally processed whole plant foods and ultra-processed foods in Brazil and can thus be used to evaluate and monitor diet quality.