Trailblazer Lecture: Why Are Processed Foods So Controversial?

Representations of Ultra-Processed Foods: A Global Analysis of How Dietary Guidelines Refer to Levels of Food Processing

BACKGROUND

As evidence grows about negative health impacts of ultra-processed foods (UPFs), nutrient-centred advice is contested, and food-based dietary guidelines are increasingly utilised. Previous analyses of dietary guidelines evaluated their potential impact on health and sustainability, but little research has been conducted to examine how the concept of UPFs is reflected in dietary advice for consumers. This paper systematically analyses whether and how UPFs are represented in dietary guidelines internationally.

METHODS

Based on a systematic online search, the consumer-targeted key messages of 106 dietary guidelines were identified and a qualitative content analysis was conducted. A coding framework was developed to classify messages as 'eat more' or 'eat less' according to the language used (eg, 'choose' vs 'avoid') and to differentiate between a focus on nutrients or food processing. Specific foods mentioned in 'eat less' guidelines were classified according to their level of processing using the NOVA framework.

RESULTS

99% of guidelines utilised some type of nutrient-based message, either promoting 'positive' nutrients (eg, vitamins) or discouraging the consumption of 'negative' nutrients (mainly salt, sugar and fat). Explicit references to food processing were present in 45% of 'eat less' guidelines and 5% of 'eat more' guidelines. Implicit references (eg, promoting 'raw' or discouraging 'packaged' foods) were found in 43% of 'eat less' and 75% of 'eat more' guidelines. 53% of the specific foods referred to in 'eat less' advice were UPFs.

CONCLUSION

Overall, nutrient-based messages were more common than messages about processing levels. The majority of discouraged foods were UPFs, however some minimally processed foods were discouraged, which points to tensions and contradictions between nutrient- and processing-based dietary advice. As dietary guidelines begin to include advice about food processing, it is important to consider both consumer understanding of the terms used and their capacity to act on the advice.

Robustness of Food Processing Classification Systems

Discrepancies exist among food processing classification systems and in the relationship between processed food intake and dietary quality of children. This study compared inter-rater reliability, food processing category, and the relationship between processing category and nutrient concentration among three systems (Nova, International Food Information Council (IFIC), and University of North Carolina at Chapel Hill (UNC)). Processing categories for the top 100 most commonly consumed foods children consume (NHANES 2013-2014) were independently coded and compared using Spearman's rank correlation coefficient. Relative ability of nutrient concentration to predict processing category was investigated using linear discriminant analysis and multinomial logistic regression and compared between systems using Cohen's kappa coefficient. UNC had the highest inter-rater reliability (ρ = 0.97), followed by IFIC (ρ = 0.78) and Nova (ρ = 0.76). UNC and Nova had the highest agreement (80%). Lower potassium was predictive of IFIC's classification of foods as moderately compared to minimally processed (p = 0.01); lower vitamin D was predictive of UNC's classification of foods as highly compared to minimally processed (p = 0.04). Sodium and added sugars were predictive of all systems' classification of highly compared to minimally processed foods (p < 0.05). Current classification systems may not sufficiently identify foods with high nutrient quality commonly consumed by children in the U.S.