Scientists have discovered unique patterns in blood and urine that can reveal how much ultra-processed food (UPF) a person eats, offering a more accurate way to track diet and its impact on health.
The study, published in *PLOS Medicine*, found that certain chemical compounds—called metabolites—can serve as biological markers for UPF consumption. These findings may help researchers and health officials better assess dietary habits and the risks linked to highly processed foods, which now make up more than half of the daily calorie intake for many Americans.
What Are Ultra-Processed Foods?
Ultra-processed foods include items like packaged snacks, sugary drinks, and frozen meals. These products are mostly made from refined ingredients and artificial additives. They have been linked to obesity, diabetes, heart disease, and some cancers.
Tracking how much UPF people eat has been difficult. Most studies rely on food surveys, which depend on memory and self-reporting. These methods can be unreliable. Also, food classification systems like Nova, which sorts foods by processing level, require detailed data that’s not always available.
To solve this problem, scientists are turning to metabolomics—the study of small molecules in the body created by digestion and metabolism. These molecules can act as clues to what people actually eat.
The Study
Researchers analyzed data from the IDATA Study, which included over 1,000 U.S. adults aged 50 to 74. For this analysis, they focused on 718 participants who provided both diet records and biological samples.
Participants completed up to six online food diaries over a year. Foods were classified by processing level using the Nova system. At the same time, researchers collected blood and two types of urine samples—one from the first morning and another from a full 24-hour period.
Using advanced testing methods, the team examined more than 1,000 compounds in these samples, covering lipids, amino acids, carbohydrates, and vitamins. They then looked for patterns that matched UPF consumption while adjusting for age, gender, race, body mass index, and smoking.
To confirm their results, they compared the data with another small feeding study. In that trial, 20 adults followed two strict diets—one with 80% UPF and one with none. Blood and urine samples from this controlled setting helped test whether the identified markers could detect real-time changes in food intake.
Key Findings
The study revealed clear differences in metabolite levels between people who ate high vs. low amounts of ultra-processed food. In total, researchers identified 191 markers in blood and 293 in urine that correlated with UPF intake.
Some compounds, like β-cryptoxanthin—a marker linked to fruit and vegetable consumption—were lower in those who ate more UPFs. Others, like N6-carboxymethyllysine, which is tied to harmful compounds called advanced glycation end-products, were higher.
Four metabolites appeared consistently in both blood and urine and may serve as strong indicators of UPF intake.
The study also found that UPF-heavy diets may introduce foreign substances, likely from food additives or packaging, and reduce intake of helpful nutrients from whole foods.
When tested in the controlled feeding trial, the new metabolite scores could distinguish between the high- and no-UPF diets with moderate accuracy. This suggests the scores could work in real-world and lab settings, though they still need refinement.
Limitations and Next Steps
The study mainly involved older, White U.S. adults, so the findings may not apply to all groups. Also, food records and sample collection weren’t always done at the same time, which could affect results. The controlled trial also had a small sample size and didn’t look at disease outcomes.
Still, researchers say these metabolite scores could become powerful tools for public health. They offer a way to measure UPF intake objectively and could help link diet to disease more clearly in future studies.
Conclusion
This research is a step forward in nutrition science. By using blood and urine markers, scientists may soon be able to track how much ultra-processed food people eat—without relying on self-reported diets. While more testing is needed in younger and more diverse populations, these findings open the door to better tools for studying diet and health.
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