Some ultra-processed foods (UPFs) – not including shop-bought bread and cereal – increase the risk of people suffering a combination of diseases such as cancer and diabetes, research suggests.
A new study found no link between ultra-processed breads and cereals, ready meals, plant-based substitutes, sweets, desserts and savoury snacks and an increased risk of suffering a combination of diseases.
But experts did find an increased risk of poorer health if people consumed lots of artificially sweetened or sugary drinks, or animal-based UPFs such as processed meat.
Researchers involved in the study included several from the International Agency for Research on Cancer, the specialised cancer agency of the World Health Organisation.
UPFs are foods that usually contain ingredients that people would not add when they were cooking homemade food.
These additions may include chemicals, colourings, sweeteners and preservatives that extend shelf life.
The most commonly eaten UPFs in Ireland are mass-produced bread, ready meals, breakfast cereals, reconstituted meat products such as ham, sweets, and shop-bought biscuits, buns and cakes.
Official guidance says not all processed food is bad, adding that some foods need processing to make them safe, such as milk, which needs to be pasteurised to remove bacteria.
The aim of the latest study was to investigate the link between UPFs and the risk of people suffering at least two chronic diseases at once from a list of cancer, cardiovascular disease and type 2 diabetes.
Experts included consideration of the Nova food classification system containing more than 11,000 food items.
The study included 266,666 people from seven European countries, 60 per cent of whom were women.
Those in the study had a 12-month food intake assessed through food frequency questionnaires, with the results showing the mean average UPF intake for men and women was 413g/day and 326g/day respectively.
This equated to 34 per cent of a man’s daily calories coming from UPFs and 32 per cent of a woman’s.
After a typical follow-up of 11.2 years, a total of 4,461 people had developed both cancer and cardiovascular disease or diabetes.
Analysis showed that those people who consumed higher amounts of UPFs had a 9% increased risk of suffering two illnesses.
But when researchers looked at subgroups of UPFs, they said the link was most notable for animal-based UPFs and artificially and sugar-sweetened beverages.
“Other subgroups such as ultra-processed breads and cereals or plant-based alternatives were not associated with risk,” they said.
The researchers said their study “provides evidence of a differential relationship of subgroups of ultra-processed foods”, adding: “Artificially and sugar-sweetened beverages, animal-based products and sauces, spreads and condiments, but not other subgroups, were associated with increased risk, suggesting that more nuanced subgroup analyses of ultra-processed foods are warranted.”
Statistical analysis even indicated there may be a reduced risk for people eating bread and cereal, which the researchers suggested could be down to their fibre content.
Lead researcher Reynalda Cordova said that for each 260g increased intake in UPF, the risk of suffering two diseases – comorbidity – rose by 9 per cent.
“With each average portion of UPF per day, the risk increases by 9 per cent,” she said.
“The risk is higher for a person who eats many portions of UPFs daily than for a person who eats very little.”
Heinz Freisling, co-author, and study lead at IARC, said the study “emphasises that it is not necessary to completely avoid ultra-processed foods; rather, their consumption should be limited, and preference be given to fresh or minimally processed foods.”
Dr Helen Croker, assistant director of research and policy at the World Cancer Research Fund, which helped fund the study, said: “What is particularly significant in this large study is that eating more ultra-processed foods, in particular animal products and sweetened beverages, was linked to an increased risk of developing cancer along with another disease such as a stroke or diabetes.
“Our cancer prevention recommendations include limiting processed foods high in fat, starches or sugars, avoiding processed meat and eating plenty of wholegrains, vegetables, pulses and fruits.”
Dr Ian Johnson, nutrition researcher and emeritus fellow at the Quadram Institute, a centre for food and health research, said the researchers recognised “that the definition of UPF covers a very broad and diverse range of foods”.
“They therefore broke the classification of UPF down into subdivisions and explored the contributions of the various different food types to the risk of developing multimorbidity,” he said.
“The ultra-processed foods most strongly associated with risk were found to be artificially sweetened and sugar-sweetened beverages, processed animal products, and sauces and condiments.
“However, a very wide range of other products, including ready-to-eat dishes, savoury snacks, and sweets and desserts were not shown to be associated with increased risk.
“Importantly, ultra-processed bread and cereal products showed an association with a reduction in risk.
“These observations do suggest a role for some UPF in the onset of multiple chronic disease, but they also show that the common assumption that all UPF foods are linked to adverse health effects is probably wrong.
“Furthermore, ultra-processed cereal products may be beneficial to health, perhaps because some provide convenient and palatable sources of dietary fibre.”
Kevin McConway, emeritus professor of applied statistics at the Open University, said the absolute level of risk of disease was not much higher in people who reported eating more UPFs.
He said: “About 17 in a group of 1,000 people like those in the study would have a diagnosis of at least two of the three conditions involved (cancer, type 2 diabetes, cardiovascular disease) during the average 11-year follow-up.
“That 17-in-1,000 figure would go up to about 18 in 1,000 (for higher UPF intake). So we’re not talking about a large increase in risk.”
