The SACN (UK) raises uncertainties on  the negative impact of processed food intakes on health.

In autumn 2022, the British Department of Health and Social Care requested to the Scientific Advisory Committee on Nutrition (SACN) to take a position regarding food processing and health. The SACN raises uncertainties on the evidence related to food processing and health in a statement published on 11 July 2023.

According to the terms of reference, the SACN reviewed the existing classifications of processed foods using the following five screening criteria:

– Could the system be applied to a UK population?

– Is there a clear, “useable” definition of the system?

– Has the system been used in peer-reviewed publications by more than one research group?

– Are there data available on inter-assessor reliability when applying the system (irrespective of the degree of inter-assessor reliability reported)?

– Has the classification been used to evaluate associations between consumption and health outcomes?

Eight food processing classification systems were identified:

• A system developed by the International Agency for Research on Cancer,
• The NOVA system developed in Brazil,
• and a variation of the NOVA system,
• A system developed by the International Food Information Council (IFIC),
• A system developed by the International Food Policy Research Institute in Guatemala,
• A system developed by the Mexican National Institute of Public Health,
• The SIGA index,
• A system developed by the University of North Carolina in 2015.

NOVA was the only system to meet all 5 screening criteria. Nevertheless, the SACN pointed some limitations.

Limitations for applying NOVA to the UK National Diet and Nutritional Survey (NDNS).

• The NDNS does not include information on low or no calorie sweeteners or other additives, nor the method of food processing or packaging. There is also a risk that researchers under- or over-estimate UPF consumption as a result of oversimplified interpretation of the NDNS food groupings.
• Moreover, the categories in the NOVA system are broad and include a wide range of foods. They group together foods with different nutritional attributes. For example, all manufactured sliced breads are classified as UPF NOVA 4 with no differentiation between white and wholemeal bread.

Limitations relating to classifications of processed foods

• The classification systems for processed foods generally did not consider the nutritional content of products or known associations between specific processed foods and health such as processed meat and cancer.
• Some systems draw on subjective concepts such as “natural”, “wholesome”, “raw”, “artisanal” and “mass produced”. These concepts may be understood differently by different users leading to potential misclassification bias.
• Systems inconsistently consider in their classification some components such as refined versus whole grains; fortified foods; additives; physical and chemical changes to food resulting from processing such as integrity of food matrix or acrylamide formation.

Limitations of the evidence on association between processed food consumption and health outcomes:

• The majority of included studies used the NOVA system for processed foods. Any limitations or biases of the NOVA classification may be replicated throughout the literature review.
• The available evidence is most exclusively observational.
• Authors of the extracted publications appeared to inconsistently adjust for key confounders or covariables. Hence, although adverse health associations were reported, it is unclear whether these associations are due to or independent of the “unhealthy” contents in nutrients such as high energy density, salt, saturated fat or free sugars.
• Evidence on the impact on population subgroups (diverse social and ethnic groups) is scarce.
• Dietary collection within observational studies was mostly based on dietary collection methods unlikely to have been designed  or validated for assessing the level of food processing.
• The method for reporting UPF consumption (in grams per day or % of energy from UPF per day) and the cut offs for the quantiles used varies across studies.

Consequently, the SACN concluded that the observed associations between higher consumption of (ultra) processed foods and adverse health effects are concerning. However, the available evidence needs to be considered with caution because of limitations in NOVA classification systems, the potential confounding factors, and the possibility that the observed associations between processed foods and health are due to the high contents in  “unhealthy” nutrients that are already taken into consideration in the existing UK dietary recommendations.

You can read the SACN statement on processed foods and health here.

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