Junk food, a blood or urine test reveals how much you eat. The danger of toxic molecule

Pre-processed foods, pre-cooked foods: processed, refined, flavored, softened and spiced. And also colorful and fragrant. What impact do they have on our body? It is the question that many do not ask themselves, because they do not know, or do not want to know, that these foods attack our health every day, even seriously. A study published in Plos Medicine has addressed the problem, a study that has identified a new way to find out how much junk food we eat every day. In practice, it is the molecules, in the blood and urine, that can reveal the amount of ultra-processed food that we insert into our body. Therefore, a blood or urine test will be enough to find out.

Junk food consumption on the rise

Both the availability and consumption of ultra-processed foods (UPF) are increasing. What are they? They are defined as "edible products, ready to eat or ready to heat, that come off industrial lines and are made primarily or entirely from ingredients extracted from whole foods, and often contain food substances of little or no culinary use and/or cosmetic additives". This is also explained by the team of researchers from the National Cancer Institute, engaged in this latest work, a group led by Erikka Loftfie , clarifying that "they represent more than 50% of the calories consumed by children and adults, and raise concerns about the potential impact on human health".

Epidemiological studies have linked UPF consumption to risk factors for chronic diseases, such as weight gain and obesity, as well as to the risk of cardiometabolic diseases and some types of cancer.

The classification

Most epidemiological studies on the consumption of ultra-processed foods have used the Nova system to classify foods based on their level of processing. “But accurate classification according to Nova requires detailed information about food sources, processing methods, ingredients, and their purposes,” the researchers explain. “However, dietary assessment tools and databases capture this information to varying degrees. As a result, it may be difficult to apply it accurately, raising concerns about misclassification, exposure, and comparability of results.” They add: “Currently, nutritional metabolomics research in population-based studies using validated assessment tools and serial blood and urine sampling to generate metabolomic data is lacking.”

Why the study was born

Therefore, the authors set as their primary objectives “to identify blood and urine metabolites associated with mean 12-month intake of ultra-processed foods (assessed using multiple 24-hour dietary recalls), and also to develop blood and urine polymetabolite scores predictive of intake of these foods.” Patients thus participated in the Interactive diet and activity tracking in AARP (IDATA) study.

But there was also a secondary objective: “To test whether these polymetabolite scores could, in the context of the randomized trial, distinguish within each person between diets containing 80% and 0% energy from processed foods.”

How the work was carried out

To do this, the researchers analyzed blood and urine samples from 718 older adults, along with detailed dietary recalls, to identify chemical fingerprints, called polymetabolite scores, that are linked to the intake of ultra-processed foods.

The study found that hundreds of metabolites in blood and urine were associated with the percentage of energy consumed from the foods in question. “We created a polymetabolite score corresponding to UPF intake, using 28 metabolites in blood or 33 in urine,” the authors note. “This score was predictive of ultra-processed food intake among participants using self-reported dietary data.” The researchers then validated the scores in a controlled dietary study, confirming that they could distinguish between high- and no-junk diets in the people they studied. (The latter hypothesis involved 20 patients admitted to the NIH Clinical Center who were subjected to high- and no-junk diets.)

“These findings could serve as objective measures of ultra-processed food intake in large population studies, to supplement or reduce reliance on dietary data,” the U.S. scientists conclude. “They could also provide new insights into their role in human health.”

The Four Processed Food Groups

The point on the foods that are the subject of the study, foods that come out of the industries super-processed and ready for consumption, is made by Dr. Raffaella Cancello , nutritionist researcher of the Department of Medical and Rehabilitation Sciences with an endocrine-metabolic focus, Laboratory of Research in Nutrition and Obesity of the Irccs - Istituto Auxologico italiano of Milan. Who explains: "The Nova classification divides foods into four groups based on their degree of industrial transformation:

1 - Unprocessed or minimally processed foods (fruits, vegetables, milk, etc.).

2 - Processed culinary ingredients (sugar, oil, salt, etc.), used for cooking.

3 - Processed foods (cheeses, hams, preserves, artisanal bread, etc.), obtained by combining foods from group 1 with ingredients from group 2.

4 - Ultra-processed foods (packaged snacks, snack foods, sugary drinks, ready meals, etc.), characterized by the presence of additives, preservatives and a low nutritional value, and whose consumption is increasingly associated with serious health risks”.

The expert continues: “Numerous scientific evidence links frequent (daily) consumption of ultra-processed foods (group 4) to as many as 32 pathologies, including obesity, diabetes and cardiovascular diseases. It is also important to underline that these products may contain carcinogenic substances or contaminants from packaging materials”.

"The positive effects of research"

Raffaella Cancello then talks about the new US study. “In this context, it represents a significant step forward in understanding the effects of ultra-processed foods on health,” she says. “The researchers have identified hundreds of metabolites present in the blood and urine that are correlated with the intake of these foods. And based on these correlations, 'scores' or polymetabolic scores have been developed that can objectively predict the consumption of ultra-processed foods.”

“This study used a large collection of dietary data, which lasted for 12 months, and the analysis of over 1,000 metabolites in a large cohort of participants,” the expert continues. “In particular, three metabolites, namely N6-carboxymethyllysine, S-methylcysteine ​​sulfoxide, and pentoic acid, were confirmed as stable and significant markers of ultra-processed food intake.”

Toxic substances from packaging to blood

There is then an aspect that Cancello defines as “particularly interesting” that emerged from the research: “It is the detection of levoglucosan in urine, a substance widely used in packaging materials derived from cellulose - he highlights -. This metabolite, used as a biopolymer in food packaging, suggests that the consumption of pre-packaged foods could expose consumers to substances deriving from packaging materials, an element often underestimated in dietary assessment”.

"The presence of a toxic molecule in urine is evidence of partial exposure and absorption - Cancello concludes -. It does not say everything about the level of risk, but it is a signal that should not be overlooked, especially if the substance is known to have long-term effects even at low doses. In the future, it will be crucial to validate these promising biomarkers in order to improve the prediction of the risk of developing chronic diseases in the case of habitual consumption of ultra-processed foods.