The studies, published in the BMJ, acknowledge that a direct link remains to be established, but they still call for policies that promote consumption of fresh or minimally processed foods over their highly processed counterparts.
Ultra-processed foods are thought to account for around 25% to 60% of daily energy intake in many countries. Previous studies have linked them to higher risks of obesity, high blood pressure, high cholesterol and some cancers, but the firm evidence is still scarce.
The first study of over 105,000 French adults showed that a 10% increase in the proportion of ultra-processed food in the diet is associated with significantly higher rates of the diseases.
In contrast, the researchers found a significant association between unprocessed or minimally processed foods and lower risks of all reported diseases.
In the second study, Spanish researchers evaluated possible associations between ultra-processed food intake and risk of death from any cause using nearly 20,000 subjects.
Its results linked the consumption of more than four servings per day of ultra-processed foods with a 62% increased risk of mortality from all causes. For each additional daily serving of ultra-processed food, mortality risk increased relatively by 18%.
The Australian reviewers said future research should explore associations between ultra-processed food and adverse health in different populations around the world, and examine how harm occurs. They also call on future government health policy to reflect the results.
“Policymakers should shift their priorities away from food reformulation—which risks positioning ultra-processed food as a solution to dietary problems—towards a greater emphasis on promoting the availability, affordability, and accessibility of unprocessed or minimally processed foods,” wrote Professor Mark Lawrence and Dr Phillip Baker, of Deakin University’s Institute for Physical Activity and Nutrition, in the BMJ.
Critics of the ultra-processed food concept argue on three points: that the definition has varied over time, that in modern societies it is unrealistic to advise people to avoid ultra-processed foods, and that reformulating the nutrient composition of processed foods is a more effective way to reduce exposure to 'risk' nutrients such as saturated fat.
Although adjustments to the definition have occurred, these were often a necessary response to an evolving evidence base on food and health and a changing food supply, the wrote.
They also argued that the view that it is better to reformulate ultra-processed foods than avoid them altogether “underplays the complexity of potential harm”. These foods deliver risk nutrients into the body, displace nutritious foods from the diet, and as the products of industrial processing they can have peculiar physical structures or chemical compositions that are also risk factors for adverse health outcomes, they said.
The findings also have implications for front-of-pack labelling, food taxation and restrictions on food marketing, which require an evidence-informed metric to determine the “healthiness” of individual food products. Currently, decisions about individual products are based on either dietary recommendations or nutrient profiling “scores,” both of which have limitations for this purpose.
“These findings add to growing evidence of an association between ultra-processed food and adverse health outcomes that has important implications for dietary advice and food policies. The dietary advice is relatively straightforward: eat less ultra-processed food and more unprocessed or minimally processed food,” the researchers added.