Sugary drinks, packaged snacks, and ready-made meals all count as ultra-processed foods — that is, foods that contain a higher number of additives and last longer because of the added preservatives. New research suggests that these foods also raise the risk of type 2 diabetes.
These foods are prevalent in Western diets, and the Western world has also seen a surge in the incidence of diabetes in recent decades. Are ultra-processed foods and type 2 diabetes linked? And if so, how?
Bernard Srour, Ph.D., of the Epidemiology and Statistics Research Center–University of Paris in France, and his team of researchers set out to answer this question.
They did so by examining the dietary habits of more than 100,000 people.
The results of their analysis appear in the journal JAMA Internal Medicine.
Srour and team carried out a population-based prospective cohort study in which they included 104,707 adult participants who had participated in the French NutriNet-Santé study. Of these participants, 21,800 were men, and 82,907 were women.
The NutriNet-Santé study spanned a decade, running from 2009 to 2019. The researchers collected data on the dietary intake of the participants using repeated 24 hour dietary records that asked them about their consumption of about 3,500 different foods.
Using the NOVA classification system, the researchers classified the 3,500 food items according to their degree of processing. There were four categories: unprocessed/minimally processed foods, culinary ingredients, processed foods, and ultra-processed foods.
The researchers used multivariable Cox proportional hazard models, which they adjusted for the known risk factors for type 2 diabetes, such as sociodemographic background, lifestyle, and medical history.
Srour and colleagues found a consistent association between the absolute amount of ultra-processed food consumption, which they measured in grams per day, and the risk of type 2 diabetes.
“In this large observational prospective study, a higher proportion of [ultra-processed foods] in the diet was associated with a higher risk of [type 2 diabetes],” conclude the authors. Srour and colleagues add:
“Even though these results need to be confirmed in other populations and settings, they provide evidence to support efforts by public health authorities to recommend limiting [ultra-processed food] consumption.”
The researchers say that ultra-processed foods are a modifiable risk factor for type 2 diabetes.
They also point to countries such as France and Brazil, whose public health authorities have already started encouraging the population to eat minimally processed foods and avoid ultra-processed ones as a precautionary measure.
The researchers did not single out one type of food or ingredient but instead looked at the cumulative effect of ultra-processed foods on type 2 diabetes risk.
The authors recommend caution in interpreting the associations that they found. Most of the additives in ultra-processed foods “are likely to be neutral for long-term health, and some may even be beneficial,” they write, giving antioxidants as an example.
However, there are other compounds that recent studies in mice and in vitro have suggested may be harmful.
For instance, “carrageenan, a thickening and stabilizing agent, […] might contribute to the development of diabetes by impairing glucose tolerance, increasing insulin resistance, and inhibiting insulin signaling,” write the authors.
Nonetheless, they caution that more research in humans is necessary before drawing conclusions about the harms of such compounds.
Chemicals such as phthalates and bisphenol A (BPA), which are often present in plastic packaging, may contaminate many ultra-processed foods.
BPA and phthalates may disrupt endocrine function, and the authors note that some recent meta-analyses have shown that high concentrations of these compounds are associated with a higher risk of type 2 diabetes.
Furthermore, research has associated metabolites that form as a result of high-temperature cooking — such as acrylamide and acrolein metabolites — with insulin resistance.
“Finally, industrial partial oil hydrogenation may lead to the creation of trans unsaturated fatty acids in products containing hydrogenated oils,” mention the authors. “Although still debated, trans fats were linked to increased risks of heart disease and [type 2 diabetes],” they note.
Nevertheless, Srour and team conclude:
“Additional research is needed to understand the biological mechanisms underlying the present observations.”