Researchers Develop Guiding Principles for Scientifically Rigorous Food Processing Classification
The Institute for the Advancement of Food and Nutrition Sciences (IAFNS) has published a set of governing principles for food formulation and processing classification systems. The principles are intended to guide researchers and decision-makers in navigating controversy and confusion surrounding food processing and formulation.
Steps considered “processing” can include cooling, heating, freezing, mixing, extruding, filtering, cooking, fermenting, drying, and forming. These processes can have positive, negative, or neutral impacts on a food’s physical, biological, or chemical characteristics. However, some food classification schemes imply that processing is inherently harmful.
Contributing to the current conversation around food processing, IAFNS formed a working group comprising government, industry, and academic scientists. This group in turn charged a separate, six-member independent writing team of public sector researchers to generate guiding principles around food processing research and classification. The principles were then vetted at an in-person, cross-sector stakeholder meeting.
Classifying Processed Foods While Keeping Science at the Forefront
The new principles call for classification systems to be transparent, reproducible, biologically plausible, and linked to health outcomes (i.e., nutrition) to distinguish processing from formulation and evolve with advancing science. They call for realism by emphasizing the need for controlled human trials instead of basing decisions on observed correlations between certain foods and health impacts. The authors note that correlation studies alone are limited in their ability to establish causation.
Specifically, IAFNS’ nine guiding principles for food formulation and processing classification systems, which are explained in a paper published in Advances in Nutrition, are:
- Documentation and definitions that allow for reproducibility, rigor, and transparency should be provided
- Properties for which there is evidence of a biological link with a health-related endpoint should be used to differentiate foods
- Associations without robust causal evidence should be considered preliminary
- The impact that processing steps have on the final composition and structure of the food in terms of a putative effect on a health-related endpoint should be considered
- The impact of formulation on the final composition and structure of the food in terms of a putative effect on a health-related endpoint should be considered
- Systems should evolve over time to reflect advancements in science and changes in the food supply, with previous versions of a system being distinguishable from updated versions
- Current scientific evaluations from scientific bodies with relevant expertise should be consulted for each iteration
- The context(s) in which a system was validated should be considered in its application
- The probative value of a research question or proposed classification system should be considered before engaging in analysis or development.
The paper also identifies research priorities and areas for investment while providing guidance on cautionary action in the absence of complete data.
Drawbacks of Popular Classifications like “Ultra-Processed Foods”
Additionally, the principles are intended to provide a shared foundation and standardized approach to help researchers advance food processing knowledge without endorsing or advocating for the creation or use of any single classification scheme. Some schemes have been criticized due to inconsistencies, ambiguities, limited evidence, misalignment with dietary guidance, and the potential for overgeneralization. A common critique of the term “ultra-processed foods,” typically referring to the NOVA classification scheme, is that it lacks clarity and is not rigorously defined.
Through their research, the authors found that some ways foods are classified are not aligned with other public health nutrition concepts. For example, in some food classification schemes, foods with added fibers fall into the category of the highest level of processing, implying they should be avoided. However, avoiding these foods may incur negative health outcomes, as fiber intake is one of the largest and most consistent nutrient gaps in the U.S. population.
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Designing Classification Schemes that are Fit-for-Purpose
Given the resource-intensive nature of developing, analyzing, or applying food classification schemes, researchers should prioritize efforts with the greatest potential for meaningful impact, the authors found.
The principles are targeted primarily to researchers who are applying classification schemes or interpreting existing science. Other audiences include users of research—such as policy professionals and other decision-makers—and developers of food classification schemes. The principles are intended to serve as a foundation to support impactful research on food classification schemes, and subsequently, public health policy.
The authors posit that food classification schemes can be developed and applied for a wide range of use cases, and they may be helpful for those implementing interventions or health policies. In this context, the principles offer a framework for assessing whether the research behind such schemes is fit-for-purpose.
