Ultraprocessed foods are often linked with higher risks of chronic disease, but one of the biggest unanswered questions is why. Is it the ingredients? The overall diet pattern? The way these foods can displace more nutrient-rich options? Or something happening in the body after people eat more of them?
A large observational study published in Critical Reviews in Food Science and Nutrition offers one possible clue. Researchers analyzed data from 15,200 participants in the European Prospective Investigation into Cancer and Nutrition, known as EPIC, and found that higher ultraprocessed food intake was associated with a distinct pattern of metabolites and fatty acids in the blood. The study does not prove that ultraprocessed foods caused those changes, but it may help researchers better understand possible biological pathways connecting highly processed diets with metabolic risk.
The researchers used diet questionnaires to estimate participants’ usual food intake, then classified foods using the NOVA system, which groups foods by level of processing. They also measured metabolites, which are small molecules involved in metabolism, along with fatty acids in participants’ blood samples.
After accounting for demographic, lifestyle and other factors, higher ultraprocessed food intake was associated with 22 circulating metabolites and eight plasma fatty acids. The pattern included higher levels of some lipid-related markers associated with impaired fatty acid oxidation and mitochondrial dysfunction, along with lower levels of several lipids involved in cell membrane stability, permeability and cell signaling.
In plain language, the study suggests that people who reported eating more ultraprocessed foods also tended to show blood-marker patterns linked with less favorable lipid processing and greater metabolic stress.
“These findings have several implications. The simultaneous decline in protective FA and the increase of metabolic stress suggest that UPF consumption may contribute to health risks through nutritional displacement and inducing metabolic disruption,” said Jessica Blanco-Lopez of the International Agency for Research on Cancer and the World Health Organization.
That wording matters. The study points to an association, not proof of cause and effect. It measured participants at one point in time, which means researchers cannot say whether ultraprocessed food intake caused the metabolic differences, whether other diet or lifestyle factors helped explain them or whether the relationship works in more than one direction.
The study also does not mean every packaged food has the same effect. Ultraprocessed food is a broad category that can include sugary drinks, packaged sweets, processed meats, ready-to-eat meals, snack foods, some breakfast cereals and some plant-based alternatives. These foods can vary widely in calories, fiber, sodium, saturated fat, added sugars, protein and overall nutrient quality.
That is one reason ultraprocessed food research can be difficult to translate for everyday readers. The practical question is not whether all processing is harmful. Processing can make foods safer, more convenient, more affordable and easier to store. The more useful question is what tends to happen when ultraprocessed foods make up a large share of the overall diet.
In this study, higher ultraprocessed food intake appeared to be tied to a blood profile that may reflect both nutritional displacement and metabolic disruption. In other words, these foods may matter not only because of what they contain, but also because of what they replace, including fiber-rich foods, fruits, vegetables, beans, nuts, whole grains and other less processed options.
“Our study underscores the potential metabolic impact of UPFs and highlights the need for further research using targeted and untargeted metabolomics approaches to clarify the biological pathways linking food processing with chronic diseases and mortality,” Blanco-Lopez said.
The researchers also reported that the results were consistent across several analytical approaches, which strengthened their confidence in the findings.
“What was particularly reassuring was that, despite these different approaches, the results remained remarkably consistent. This gave us greater confidence in the robustness and reliability of the findings,” Blanco-Lopez said.
Still, blood markers are not the same as health outcomes. This study did not show that participants developed type 2 diabetes, heart disease, cancer or another chronic condition because of these metabolic patterns. Instead, it adds to the evidence that higher ultraprocessed food intake may be linked with measurable differences in the body.
This research was supported by World Cancer Research Fund International, Institut National du Cancer and multiple European public health, cancer research, university and government research organizations connected with the EPIC study. Coordination of EPIC-Europe is funded by the International Agency for Research on Cancer and Imperial College London, with additional infrastructure support from the UK National Institute for Health and Care Research Imperial Biomedical Research Center.