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‘Uncertainties’ over quality of evidence linking ultra-processed foods to poor health

A UK government report has cast doubt on the science linking consumption of ultra-processed foods (UPFs) with increased risks of poor health, highlighting “uncertainties around the quality of evidence available”.

In its assessment, the Scientific Advisory Committee on Nutrition (SACN) concluded that previous studies were almost exclusively observational.

In addition, confounding factors, or key variables such as energy intake, body mass index, smoking, and socioeconomic status, could not be adequately accounted for.

It also identified NOVA – the most commonly used classification system for processed foods – as the only system that met the SACN’s initial screening criteria and thus potentially suitable for use in the UK, despite a limitation that identified very broad categories and a tendency to capture a wide range of foods.

SACN recognises UPF link to poor health is ‘concerning’

“The observed associations between higher consumption of (ultra-)processed foods and adverse health outcomes are concerning,” the SACN acknowledged in a position statement.

“However, the limitations in the NOVA classification system, the potential for confounding, and the possibility that the observed adverse associations with (ultra-)processed foods are covered by existing UK dietary recommendations mean that the evidence to date needs to be treated with caution.”

The SACN’s findings were met with a mixed response from the food and nutrition community.

Chair of trustees Professor Judy Buttriss and trustee Professor Christine Williams, both from the Academy of Nutrition Sciences, pointed to the lack of evidence about the mechanism(s) via which processed foods might adversely affect health.

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“[There] is a need for good-quality randomised controlled trials that may help establish potential mechanisms and establish whether they are independent of energy density or other dietary factors,” they said.

“Furthermore, as the NOVA system does not consider nutrient contribution of foods, it fails to accurately distinguish processed foods with limited nutritional attributes from processed foods with recognised nutritional properties, many of which contribute to the nutrient intakes of families living on tight budgets.”

What is the NOVA system and where has it been adopted?

The NOVA system, which was first proposed in 2009, classifies food into four groups based on the type of processing.

These are unprocessed and minimally processed foods; processed culinary ingredients; processed foods; and “ultra-processed” foods.

Countries that use the NOVA system include Brazil (updated in 2014 and currently still in use) and France, which has shaped its public health nutritional policy goals for 2018-22 to reduce consumption of group four UPFs by 20%.

But the SACN’s latest findings have enraged other commentators, who highlighted the committee's position and the conflict of interests among its members.

Particularly scathing in his response was the Soil Association’s head of food policy, Rob Percival, who initially welcomed the review, particularly the committee’s commitment to keeping the science under review.

“Some of SACN’s suggestions are entirely sensible, such as the recommendation that the National Diet and Nutrition Survey should be revised to better gather data on national intake of ultra-processed products,” he added.

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“Government should act on this recommendation and invest in further research to better understand the risks posed by ultra-processing.”

Soil Association highlights industry ties and conflicted financial interests

However, Percival said the “sticky fingers of the ultra-processed food industry” could be seen all over the position statement, highlighting industry ties, conflicted financial interests, and a “narrow framing of the science”.

He also revealed that the UK government was also promoting UPF products via its own healthy eating tool – the Food Scanner app.

In response, Gunter Kuhnle, professor of nutrition and food science at the University of Reading, said: “SACN is very transparent in their approach – which makes it easy to comment on the science.

“Clearly, there's not much to criticise, otherwise there wouldn't be so many ad hominem attacks (by people who are too scared for open discussions).”