Updated Feb. 28 to include study limitations.

Increased consumption of ultra-processed foods is associated with higher risk of all-cause mortality, according to the results of a study published earlier this month in JAMA Internal Medicine.

The authors analyzed dietary records and other data from the French NutriNet-Santé Study, an ongoing cohort study investigating the relationship between nutrition and health. The subjects of the current analysis were nearly 45,000 French adults 45 years or older. Almost three-quarters were women and the average age at baseline was 56.7 years.

Ultra-processed foods were defined according to the NOVA food classification system, which categorizes foods based on “the extent and purpose of food processing, rather than in terms of nutrients.” In this system, ultra-processed foods are industrial formulations that typically have five or more ingredients, as well as ingredients not commonly used in culinary preparations. The category includes everything from carbonated drinks to margarine, cookies, hot dogs, breakfast cereals, and many ready-to-heat products.

For the subjects in the study, ultra-processed foods made up an average of about 14% of total food consumed by weight and 29% of total energy intake. Subjects who ate more ultra-processed foods tended to be younger, less educated, less active, and living alone, as well as have a lower income and a higher body mass index.

After adjusting for confounding factors, the researchers found that a 10% increase in the proportion of ultra-processed food consumption was linked to a 14% higher risk of all-cause mortality.

They concluded that “an increase in ultra-processed foods consumption appears to be associated with an overall higher mortality risk among this adult population,” and recommended “further prospective studies…to confirm these findings and to disentangle the various mechanisms by which ultra-processed foods may affect health.”

The study’s conclusions are startling, especially because ultra-processed food consumption in the United States is almost 60%, much higher than for the subjects in the study. And while it does add to growing evidence that some ultra-processed foods are associated with negative health consequences, it also has several significant limitations. Here they are, as identified by the International Food Information Council (IFIC) Foundation:

  • The “ultra-processed” category included “a wide variety of foods with varying nutritional profiles,” some of which have desirable benefits. Lumping them together makes it impossible to determine which foods or ingredients are associated with mortality risk.
  • The sample group isn’t representative of the population as a whole.
  • The authors acknowledge the possibility that foods were mis-categorized.
  • The diseases assessed take decades to develop, but the participants were tracked for only 7 years, so it’s impossible to know whether the health outcomes were related to intake during the study or over the course of participants’ lifetimes.
  • Observational studies can’t establish cause-and-effect relationships.