‘Uncertainties’ over studies linking ultra-processed food to poor health

Previous research has linked ultra-processed foods such as ice cream, ham, crisps, mass-produced bread and breakfast cereal to a number of poor health outcomes, including an increased risk of some cancers, weight gain and heart disease.

But experts on the Government’s Scientific Advisory Committee on Nutrition (SACN) said there are “uncertainties around the quality of evidence available”.

The academics said the observed associations are “concerning” but called for more studies to thoroughly investigate the link.

Part of the issue is it is tricky to define what counts as an ultra-processed food, they said.

This could mean that when studies are conducted, researchers might have different definitions of what an ultra-processed food is and may not come to the same conclusions as someone using a different classification.

While some have tried to come up with classification systems, experts said there are “concerns around practical application in the UK” about the most widely used system, known as Nova.

As a result, the experts called for a food classification system that can be used to assess whether or not foods consumed in the UK are ultra-processed.

This could also help future research looking into the links between ultra-processed food and poor health outcomes.

The committee concluded: “The systematic reviews identified have consistently reported that increased consumption of (ultra-)processed foods was associated with increased risks of adverse health outcomes.

“However, there are uncertainties around the quality of evidence available.

“Studies are almost exclusively observational and confounding factors or key variables such as energy intake, body mass index, smoking and socioeconomic status may not be adequately accounted for.”

It said consumption of ultra-processed foods “may be an indicator” of other unhealthy dietary habits and lifestyle behaviours.

It added: “The observed associations between higher consumption of ultra-processed foods and adverse health outcomes are concerning – 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 committee called for more studies into the topic and the “development of an ultra-processed foods classification system that can reliably be applied to estimate consumption of processed foods in the UK”.

Commenting on the SACN update, Dr Ian Johnson, nutrition researcher and emeritus fellow at the Quadram Institute, said: “This careful review comes from a highly reputable advisory group using rigorous methods to analyse the current literature on the relationship between consumption of ultra-processed foods and health.

“It confirms that dietary patterns defined in this way are often associated with higher risks of non-communicable diseases, but it also illustrates the many uncertainties that arise because the concept of ultra-processed food (UPF) is very broad and poorly defined.

“This makes it extremely difficult to identify and quantify the mechanisms linking UPF diets and poor health outcomes. The subject requires further research and refinement.”

Gunter Kuhnle, professor of nutrition and food science at the University of Reading, said: “The statement makes it clear that processed and ultra-processed foods are a much more complex issue than previous reports suggest – and clearly not as dangerous as often implied.

“The evidence base for adverse effects is based on a small number of observational studies that have known limitations: ultra-processed foods might be an indicator of an overall unhealthy lifestyle.

“The SACN statement highlights a number of limitations when assessing intake of ultra-processed foods: a lot of the information needed to identify a food as ultra-processed are not generally collected. For example, in most studies it is impossible to distinguish between home-made, artisanal or mass-produced breads, although only the latter is considered ‘ultra-processed’.

“This SACN statement puts many of the often-outrageous claims about ultra-processed foods into context.”

Dr Duane Mellor, registered dietitian and senior lecturer at Aston Medical School, said: “It is good to see this report from SACN which highlights that although there are consistent findings of associations between consuming of ultra-processed foods with poor health including risk of cardiovascular disease, it clearly also states there are limitations with what is meant by an ultra-processed food.

“It is also good to see that the SACN report acknowledges that in the research they looked at, often individuals who are said to consume more ultra-processed foods would be eating a diet that would be consider to be generally less healthy – which could simply mean that it might be overall nutritional quality of the diet that is the issue, rather than the processing of the food itself.”

A Department of Health and Social Care spokesperson said: “We have noted the Scientific Advisory Committee on Nutrition’s position statement on processed foods and health, which aligns with the firm action we are taking against foods high in saturated fats, salt or sugar.”