A blood test of more than 6,000 British adults revealed two contrasting chemical patterns: one linked to ultra-processed diets, and another tied to diets built around minimally processed foods. The patterns may help explain why the way food is made, not only its sugar, salt and fat content, could matter for long-term health.
Researchers from University College London and Imperial College London studied participants in the Whitehall II project, a group of British civil servants recruited in the 1980s. Participants provided blood samples and answered questions about their diets. Their health was followed for up to 20 years. The findings were published in BMC Medicine.
The team measured 233 metabolites, tiny molecules produced as the body processes food and carries out other chemical reactions. Using machine learning, they identified 34 metabolites most closely linked to an ultra-processed diet and 50 linked to a minimally processed diet. Eight appeared in both patterns.
The ultra-processed pattern included lower levels of omega-3 fatty acids and HDL, often called “good” cholesterol, and higher levels of triglycerides carried by very-low-density lipoproteins. When these blood fats are present in excess, they can contribute to clogged arteries. The pattern linked to minimally processed foods showed the opposite trend, with more healthy fats and fewer unhealthy ones.
These molecular signatures accounted for 43% to 51% of the relationship between diet and the risk of cardiovascular disease and type 2 diabetes. The link remained even after researchers accounted for the higher sugar, fat and salt levels in the ultra-processed diets they studied. That does not prove that processing causes disease, but it suggests that nutrition labels may not tell the whole story.
The long-term health results also pointed in different directions. Over two decades, people in the highest third for ultra-processed food intake had a 17% higher risk of cardiovascular disease than people in the lowest third. Those in the highest third for minimally processed food intake had a 19% lower risk of cardiovascular disease and a 40% lower risk of type 2 diabetes, compared with the lowest third.
Lead author Dr. Eunice Wang, who did the research as a Ph.D. student at UCL, said the findings hint that processing itself may play a role, while stressing that more research is needed. The study tracked real-world diets rather than testing a specific food in an experiment, so it cannot show that processing alone caused the different risks.
The results come as the U.K.’s Scientific Advisory Committee on Nutrition reviews evidence on ultra-processed foods. Current U.K. dietary guidance focuses on limiting foods high in sugar, salt and saturated fat, rather than treating processing as a separate risk. Senior author Professor Clare Llewellyn said the study adds evidence for future policy discussions about whether processing should be considered alongside a food’s nutritional content. For now, the blood signatures offer researchers a new way to investigate what sits between the foods people eat and their health over time.