Molecules in blood and urine may reveal how much energy a person consumes from ultraprocessed foods, a key step to understanding the impact of the products that make up nearly 60% of the American diet, a new study finds.
It’s the first time that scientists have identified biological markers that can indicate higher or lower intake of the foods, which are linked to a host of health problems, said Erikka Loftfield, a National Cancer Institute researcher who led the study published in the journal PLOS Medicine.
“It can potentially give us some clues as to what the underlying biology might be between an ultraprocessed food association and a health outcome,” Loftfield said.
Potato chips are displayed in pharmacy Duane Reade by Walgreens on March 25, 2021, in New York.
Ultraprocessed foods — sugary cereals, sodas, chips, frozen pizzas and more — are products created through industrial processes with ingredients such as additives, colors and preservatives not found in home kitchens. They’re ubiquitous in the U.S. and elsewhere, but studying their health impacts is hard because it’s difficult to accurately track what people eat.
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Typical nutrition studies rely on recall: asking people what they ate during a certain period. But such reports are notoriously unreliable because people don’t remember everything they ate, or they record it inaccurately.
“There’s a need for both a more objective measure and potentially also a more accurate measure,” Loftfield explained.
To create the new scores, Loftfield and her colleagues examined data from an existing study of more than 1,000 older U.S. adults who were AARP members. More than 700 of them provided blood and urine samples, as well as detailed dietary recall reports, collected over a year.
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The scientists found that hundreds of metabolites — products of digestion and other processes — corresponded to the percentage of energy a person consumed from ultraprocessed foods. From those, they devised a score of 28 blood markers and up to 33 urine markers that reliably predicted ultraprocessed food intake in people consuming typical diets.
“We found this signature that was sort of predictive of this dietary pattern that’s high in ultraprocessed food and not just a specific food item here and there,” she said.
A few of the markers, notably two amino acids and a carbohydrate, showed up at least 60 times out of 100 testing iterations. One marker showed a potential link between a diet high in ultraprocessed foods and type 2 diabetes, the study found.
To confirm the findings, Loftfield measured the scoring tool with participants in a carefully controlled 2019 National Institutes of Health study of ultraprocessed foods.
Ultraprocessed foods — sugary cereals, sodas, chips, frozen pizzas and more — are products created through industrial processes with ingredients such as additives, colors and preservatives not found in home kitchens.
In that study, 20 adults went to live for a month at an NIH center. They received diets of ultraprocessed and unprocessed foods matched for calories, sugar, fat, fiber and macronutrients for two weeks each and were told to eat as much as they liked.
Loftfield’s team found that they could use the metabolite scores to tell when the individual participants were eating a lot of ultraprocessed foods and when they weren’t eating those foods.
The results suggested the markers were “valid at the individual level,” Loftfield said.
It’s still early research, but identifying blood and urine markers to predict ultraprocessed-foods consumption is “a major scientific advance,” said Dr. Dariush Mozaffarian, director of the Food Is Medicine Institute at Tufts University, who was not involved in the study.
“With more research, these metabolic signatures can begin to untangle the biologic pathways and harms of UPF and also differences in health effects of specific UPF food groups, processing methods and additives,” he said.
Loftfield said she hopes to apply the tool to existing studies where blood and urine samples are available to track, for instance, the effect of consuming ultraprocessed foods on cancer risk.
At a time when support for government research is being cut, funding remains uncertain.
“There’s a lot of interest across the board — scientifically, public interest, political interest — in the question of: Does ultraprocessed food impact health and, if so, how?” she said. “How can we fund the studies that need to be done to answer these questions in a timely way?”
Americans love frozen meals and processed foods. We still don't fully understand what it's doing to our bodies.
Americans love frozen meals and processed foods. We still don't fully understand what it's doing to our bodies.
Over the past two decades, ultra-processed foods have grown to make up a majority of Americans' daily calorie intake, and a growing body of research suggests these cheaper eats could be costing us our lives.
analyzed resources from , , , and academic studies to break down the less savory side of the highly processed foods in grocery stores.
An early study that analyzed more than 9,000 people's diets found that in 2010, the majority of Americans' caloric intake had grown to .
Ultra-processed foods are in every aisle of the grocery store. They're in the bread aisle lurking in prepackaged baked items, in the breakfast aisle in cereals, and at the deli counter in sliced lunch meats. They also include the frozen ready-to-eat meals that have seen steady demand in recent years, prompting retailers to expand their number of aisles. Frozen french fries and onion rings, baked goods like frozen cookies, and , according to a 2023 report from the Food Institute.
The growing prevalence of processed foods in the American diet is sometimes due to reasons out of people's control. These foods appeal to our palates, but for those with limited incomes and little time for cooking, they're also affordable and tend to be convenient to prepare.
Despite the risks associated with these foods, a survey conducted by the International Food Information Council in July 2023 found that 7 in 10 Americans . It's a distinction that researchers have noted isn't often clarified in nutritional education or packaging.
The difference between processed and ultra-processed foods
Unprocessed or minimally processed foods typically include whole foods like fresh fruits, vegetables, eggs, fish, and nuts. Any time a whole food is significantly changed from its original state, at least some "processing" of that food has to occur. The processing can be chemical, in which added chemicals change the state of the food, or mechanical, whereby the food changes shape, texture, and appearance.
Experts at suggest that many minimally processed foods can be a nutritious part of our diets, including items like frozen fruits and vegetables or whole foods that have been canned. Foods fall into the "ultra-processed" category when they contain artificial flavors, colors, or additives that boost the saturated fat, sugar, and salt content well above that of the original ingredients.
Take the universally enjoyed chicken nugget, a processed food that has become a staple in children's diets. Chicken nuggets are made by deboning a chicken and grinding up the meat into a paste combined with chemicals, preservatives, and even food coloring before it's shaped into nuggets and deep-fried in oil. Other common ultra-processed foods include canned meats and deli meats, pizza, ice cream, canned soups, and potato chips.
A modern diet costing billions and contributing to chronic illness affecting millions
Studies over the past decade have suggested that the evolution of American diets to include more processed foods may have expensive and deadly ramifications.
Unhealthy eating contributed to more deaths than smoking cigarettes—around 11 million globally each year, according to a from 1990-2017 published in 2019. Other research has with the risk of premature death, diabetes, heart disease, and even dementia.
Researchers from the Tufts Institute for Global Obesity Research and other research institutions studying the dietary intake of young people suggested a link between ultra-processed diets and the in a 2021 study. The National Heart, Lung, and Blood Institute reports that . The condition can put them at increased risk for other diseases like diabetes, cancer, heart disease, and breathing problems.
Diet-related obesity and other diseases can also contribute to poor mental health outcomes linked to their condition and due, at least in part, to stigmas surrounding obesity. The potential causes of obesity can be complex and include genetic predisposition, environmental factors, and dietary intake. Studies suggest between 20%-60% of people living with obesity , including depression and anxiety, a higher percentage than the overall population.
Diets are contributing to higher health care costs in the U.S. Diet-related diseases like heart disease and diabetes in health costs, according to 2019 research from the National Institutes of Health. That cost burden is shouldered not only by taxpayers but also by patients themselves.
