Ultra-processed foods (UPFs) have become a large share of the modern diet, especially in the United States, where they make up more than half of the daily calorie intake. These ready-to-eat or ready-to-heat products comprise packaged snacks, sugary drinks, instant meals, and a great number of fast foods. Usually, they are made by industrial methods and contain ingredients that are hardly found in a normal kitchen, such as emulsifiers, flavour enhancers, and refined sugars. Studies have repeatedly shown that a high intake of UPFs is associated with weight gain, obesity, cardiovascular diseases, and some types of cancer. Nevertheless, it has been a long-standing problem in nutrition science to find a precise way to determine the amount of ultra-processed food in people’s diets.A study published by the US National Institute of Health shows how your blood and urine can reveal your junk intake.
Metabolites in blood and urine can reveal your junk intake
To conquer such issues, the research community has been progressively inclined to the study of metabolomics. Metabolites are minor compounds generated during the degradation of food in the body and its conversion into energy. Their amounts in the blood and urine are representations of both the most recent and the usual dietary intake, thus providing a biological picture of the person’s diet. It was the scientists’ idea that particular metabolite fingerprints might be used as a measure to monitor the intake of highly processed food objectively.
Why measuring ultra-processed food intake is difficult
Most of the big diet studies are based on self-reported food questionnaires. Although these instruments are convenient, they have significant shortcomings. Individuals may not remember what they ate, may give smaller estimates of their portion sizes, and may also wrongly classify foods. What is more, dietary surveys are frequently very lacking in details which are required to establish how the foods were processed and the industrial ingredients they contain. Hence, it becomes a challenge to accurately measure the consumption of ultra-processed foods, which, in turn, weakens the associations between diet and the risk of diseases.
Linking metabolites to ultra-processed foods
Researchers first determined the percentage of calories that each participant got from ultra-processed foods during the study period based on the dietary data. After that, they compared these numbers with metabolite levels of blood and urine samples. The study found that UPF consumption was correlated with hundreds of metabolites, including lipids, amino acids, carbohydrates, and vitamins, to a large extent. To translate the results into everyday language, the group employed a machine learning algorithm to pinpoint the most informative metabolites and then combined them into “poly-metabolite scores”. There were 28 metabolites chosen for blood samples and 33 for urine samples. A few metabolites were inversely correlated with UPF consumption and were related to foods like vegetables. In contrast, some metabolites were directly correlated and consisted of compounds produced during sugar–protein reactions that have been associated with diabetes and cardiometabolic disease risk.
Testing the accuracy of poly-metabolite scores
The researchers confirmed their method with the information from a controlled feeding trial at the NIH Clinical Center. The study involved 20 participants who were on either an ultra-processed or a minimally processed diet for two weeks and then changed to the other diet. Poly-metabolite scores from blood and urine samples after each phase were able to differentiate readily between high and low ultra-processed food diets, even within the same individual.
Why this research matters
This method based on metabolites is a strong new instrument for nutrition research. The main benefit is that it lessens the dependence on self-reported dietary data and the associated biases by giving an objective measure of ultra-processed food intake. Moreover, it allows to comprehend the effect of UPFs on metabolism and overall health much better.
Limitations and future research
While the findings are encouraging, the research is limited. A majority of the participants were elderly and Caucasian; thus, the poly-metabolite scores require validation in different populations. Subsequent studies will refine these markers and evaluate their application in various age groups, ethnicities, and dietary patterns.Ultra-processed foods are a major factor leading to poor diet quality and increased risk of chronic diseases. The use of metabolites in blood and urine as an objective measure of UPF intake is a major step forward in nutritional science. Eventually, this method can be a source of improvement for dietary guidelines, a tool for public health research, and a means to elucidate the real health effects of ultra-processed foods.
