Ultra-Processed Foods Now Linked to Risk of Type 2 Diabetes

Nancy A. Melville

December 16, 2019

High consumption of so-called ultra-processed foods is associated with an increased risk of type 2 diabetes, independent of other risk factors including weight and nutritional quality of the diet, a new study indicates. The results suggest a possible modifiable target for prevention of diabetes, say the authors.

"To our knowledge, although ultra-processed foods consumption was previously found to be associated with increased risks of cancer, cardiovascular diseases, mortality, depressive symptoms, and metabolic disorders, no prior prospective epidemiological study had evaluated their association with type 2 diabetes risk," write Bernard Srour, PharmD, MPH, PhD, and colleagues in their article published online today in JAMA Internal Medicine.

The study involved 104,707 participants in the ongoing, web-based NutriNet-Santé study in France, the majority of whom were women (79.2% vs 20.8%).

Participants, who were a mean baseline age of 42 years, provided repeated 24-hour dietary records on their consumption of more than 3500 food items. They also reported on major health events, including type 2 diabetes; the findings were further confirmed using medication reimbursement data.

Rates of type 2 diabetes among the lowest and highest ultra-processed foods consumers were 113 and 166 per 100,000 person-years, respectively.

Over a median follow-up of 6 years, the consumption of ultra-processed foods was found to be associated with a significantly higher risk of type 2 diabetes, with a hazard ratio (HR) of 1.15 for each 10% increase of ultra-processed foods in the diet.

The study was supported by the French Ministry of Health, Public Health France, National Institute of Health and Medical Research (INSERM), National Institute for Agricultural Research (INRA), National Conservatory of Arts and Trades (CNAM), and the University of Paris.

Highly Processed Foods Association With Diabetes, Not Just Weight Gain

The results remained significant after adjusting for factors including nutritional quality of the diet, other metabolic comorbidities (HR, 1.13), and importantly, weight change (HR, 1.13).

A recent National Institutes of Health study, also reported by Medscape Medical News, linked consumption of highly processed foods to overeating and weight gain, but these latest findings suggest effects independent of weight gain linking this type of food to diabetes risk, say the French researchers.

"Even if participants did not gain weight during follow-up, they were at risk of developing diabetes if their ultra-processed [food] consumption was higher," Srour, of the Nutritional Epidemiology Research Team, INSERM, INRA, University of Paris, France, told Medscape Medical News.

The absolute amount of ultra-processed foods consumption, in terms of grams per day, was further associated with type 2 diabetes risk, even after adjusting for the intake of unprocessed or minimally processed foods (HR, 1.05 for a 100 g/day increase).

"Even though the consumption of un- or minimally processed foods is associated with a lower type 2 diabetes risk, the association between ultra-processed foods and a higher risk of type 2 diabetes is not fully due to a lower simultaneous consumption of un/minimally processed food," Srour noted.

As also recently reported by Medscape Medical News, Srour and colleagues published work, also from the NutriNet-Santé study, showing a 10% higher intake of ultra-processed foods and beverages was associated with about a 12% increased risk of cardiovascular disease, coronary heart disease, and cerebrovascular disease over approximately 5 years.

The team has also reported links between ultra-processed foods and an increased risk of cancer, mortality, depressive symptoms, and inflammatory bowel syndrome.

Proposed Mechanisms Range From Poor Nutrition to Chemical Additives

Srour and colleagues propose a variety of mechanisms that might explain the link between higher consumption of ultra-processed foods and risk of type 2 diabetes.

In terms of nutrition, processed foods are known to have poorer quality, containing higher levels of sodium, energy, fat, and sugar, and they are lower in fiber, while also commonly having a higher glycemic index, the authors note.

Other mechanisms, however, may include alteration of gut microbiota and endocrine disruption because of the food production process and packaging.  

Processed food products, for instance, often have longer shelf-lives because of the use of preservatives, and therefore have longer exposure to harmful chemicals such as endocrine-disrupting phthalates and bisphenol A, the latter of which was associated with type 2 diabetes risk in a recent meta-analysis.

Other physical and chemical processes, such as high-temperature heating, are associated with the production of contaminants posing health risks, such as acrylamide, found mainly in fried potatoes, biscuits, cakes, and coffee, which have been associated with insulin resistance.

"Ultra-processed foods usually go through several physical and chemical processes such as extruding, molding, pre-frying, (or) hydrogenation, possibly leading to the production of new compounds with potential cardiometabolic disruption properties," the authors write.

"They also typically contain food substances of no or rare culinary use (eg, some varieties of refined sugars, hydrogenated oils) and various types of cosmetic additives (eg, emulsifiers, sweeteners, thickening agents, colorants), with cardiometabolic effects postulated for some," they continue.

Highly Processed Foods: "We Continue to Eat Them"

Leading ultra-processed food culprits include sugary and artificially sweetened sodas, energy drinks, industrial dairy desserts and milkshakes, fats and sauces, sugary products, such as candies and chocolate, and processed meat, a well-known risk factor for type 2 diabetes, Srour noted.

And even putting aside mechanisms for their role in disease, one thing appears clear from a recent small, but intriguing, study: ultra-processed foods are designed to make us want more, and so far manufacturers are succeeding in their aim to increase consumption.

As discussed in a recent Medscape commentary, the study involved volunteers who were given ultra-processed diets for 2 weeks and diets with unprocessed foods for a separate 2 weeks, with equally abundant portions of food in each arm.

Remarkably, when on the ultra-processed foods diet, participants consumed an average of 500 calories/day more than on the unprocessed diet and gained about a kilogram along the way, while they lost about a kilogram during the unprocessed foods period.

The study underscores that "through feats of science and engineering, corporations have created foods that smack us right in the pleasure centers of the brain, and we continue to eat them even after we shouldn't," noted F. Perry Wilson, MD, an assistant professor in the Department of Medicine, Yale School of Medicine, New Haven, Connecticut, the author of a commentary.

"Maybe this is one of those things that if we simply acknowledge, we can avoid," Wilson concluded.

JAMA Internal Medicine. Published online December 16, 2019. Abstract

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