A high proportion of ultra-processed foods in the diet is associated with a greater risk of developing type 2 diabetes, a new study suggests.
Ultra-processed foods (UPFs) like sugary sweetened beverages and processed meats are widespread in Western diets.
Previous studies have linked their consumption to an increased risk of all-cause mortality and chronic diseases such as cancer and cardiovascular disease.
But new research published in JAMA Internal Medicine has now looked at how such diets relate to diabetes.
In an observational study of 21,800 men and 82,907 women, scientists found absolute type 2 diabetes rates in the lowest UPF consumers were 113 per 100,000-person-years compared with 166 per 100,000-person-years for those who ate the highest UPF levels.
Participants were aged 18 years or older from the French NutriNet-Sante cohort (2009-2019).
Data on dietary intake was collected using repeated 24-hour dietary records designed to register participants’ usual consumption for more than 3,500 different food items.
These were categorised according to their degree of processing by the Nova classification system, which rates foods according to the extent and purpose of food processing, rather than in terms of nutrients.
For each participant, the proportion of UPF in the total weight of food and/or drinks consumed was calculated in grams per day.
Researchers then measured what percentage of the diet comprised of UPFs and on average these made up 17.3% of the food consumed.
The research suggests that a 10% increase of ultra-processed foods in the diet was linked to a 15% higher risk of type 2 diabetes.
In a follow-up six years later, 821 participants had got type 2 diabetes.
The results held true even when other factors that might influence the results – such as obesity and exercise levels – were taken into account.
The authors, including Dr Bernard Srour of the Epidemiology and Statistics Research Centre-University of Paris, wrote: “These results suggest an association between UPF consumption and type 2 diabetes risk.
“They need to be confirmed in large prospective cohorts in other settings, and underlying mechanisms need to be explored in ad-hoc epidemiological and experimental studies.
“Beyond nutritional factors, non-nutritional dimensions of the diet may play a role in these associations, such as some additives, neoformed contaminants, and contact materials.”
Professor Kevin McConway, emeritus professor of applied statistics at The Open University, said: “The new study does not really throw much new light on how ultra-processed food consumption might possibly be a cause of changes in diabetes risk.
“The possible causal pathways from the foods to the diabetes do not apply to every food on the ultra-processed list, so it would need analysis of individual foods or groups of foods to throw clearer light on what might be going on, and despite the 100,000 participants, there isn’t really enough data for most such investigations.”
Dr Duane Mellor, a registered dietitian and senior teaching fellow, at Aston Medical School at Aston University in Birmingham, said: “The study is clear that it does not show that this link is causal, it is only an association.
“There are some confusing aspects, in that the statistics try to take out the effect of the diet quality measured using the UK Food Standard’s Agency model for foods high in fat, sugar and salt, which is the one used in the advertising ban on the Transport of London estate.
“This is problematic as the authors suggest one reason that ultra-processed foods may increase risk of type 2 diabetes is because of the fat, sugar and salt.
“This should not be shown in the statistics as it seems that it should have been accounted for in the statistical modelling.”
