What we eat may leave clues in our blood about our long-term health. New research suggests those clues could help explain why diets high in ultraprocessed foods are associated with a greater risk of heart disease and type 2 diabetes.
In a study published in BMC Medicine, researchers examined blood samples from more than 6,000 British adults and followed their health for up to 20 years. They found that certain blood patterns associated with eating more ultraprocessed foods were also connected to a higher likelihood of developing both conditions. However, the observational study doesn't prove that food processing itself causes disease.
Previous research has identified distinctive blood patterns associated with ultraprocessed diets. This study takes that work further by examining whether those patterns are associated with disease diagnoses years later.
Researchers from University College London and Imperial College London used data from 6,010 participants in a long-running British health study. They examined participants' eating habits and measured 233 substances in their blood, including different types of fats and compounds involved in the body's everyday functions.
They identified two patterns: one associated with eating more ultraprocessed foods and another associated with eating more minimally processed foods, such as fruits, vegetables, beans and fish.
People whose blood patterns reflected higher ultraprocessed food consumption generally had lower levels of omega-3 fatty acids and less favorable cholesterol and blood-fat profiles. Those whose patterns reflected more minimally processed foods tended to show the opposite.
Over the following decades, researchers documented 1,094 cases of cardiovascular disease and 853 cases of type 2 diabetes.
Participants who ate the most ultraprocessed foods had a 23% higher relative risk of cardiovascular disease and an 18% higher relative risk of type 2 diabetes compared with those who ate the least, even after researchers accounted for several other health and lifestyle factors.
The blood patterns themselves were also associated with a greater likelihood of developing these conditions. Interestingly, those connections remained even after accounting for differences in sugar, fat, sodium and fiber intake.
That suggests the relationship between diet and chronic disease may be more complicated than simply looking at how much sugar, salt or saturated fat someone eats.
Researchers estimated that the blood patterns could statistically account for roughly 43% to 51% of the observed connections between eating patterns and later disease. But that doesn't mean they caused half the risk. The study couldn't establish cause and effect, and other dietary or lifestyle factors may also play a role.
It also remains unclear whether food processing itself contributes to these relationships. As previous research has highlighted, separating the effects of processing from the nutritional characteristics of foods is difficult.
Another interesting finding was that not all ultraprocessed foods showed the same associations.
Ultraprocessed meats and drinks were associated with higher risks of both cardiovascular disease and type 2 diabetes. Ultraprocessed breads, however, were associated with a lower risk of type 2 diabetes. Other categories showed no significant associations with either condition.
That doesn't mean ultraprocessed bread prevents diabetes. But it does reinforce that foods classified as ultraprocessed can differ considerably in their nutritional qualities and potential health effects.
The study also has limitations. Participants reported their diets during the 1990s, when food products and eating habits were different from today. Most were middle-aged British civil servants, and the majority were White men, meaning the findings may not apply equally to everyone.
The results add to growing evidence that dietary patterns are associated with differences in metabolic health, but researchers still have work to do to understand what's driving those connections. The findings also suggest that when evaluating ultraprocessed foods, looking at what's in them and how they fit into the overall diet remains important.
The Whitehall II study received funding from the UK Medical Research Council and the Wellcome Trust.