It's clear that they are linked to bad health.
Scientists are just now starting to figure out why, though.
In the middle of the 1990s, Carlos Monteiro, a nutritional epidemiologist in Brazil, made a startling discovery: the prevalence of obesity among youngsters in his nation was fast increasing.
In an effort to gain a better understanding of the reason for this, he and his colleagues at the University of São Paulo conducted a thorough examination of the data pertaining to the purchasing habits of Brazilian families over the last several years. According to the study's findings, individuals were shopping for more processed goods such as sodas, sausages, instant noodles, packaged breads, and cookies while purchasing less sugar, salt, cooking oils, and basic foods such as grains and beans that they had previously purchased.
Dr. Monteiro said that in order to provide a description of the second type of food, the group brought a new word into the scientific literature, which they referred to as ultraprocessed foods, or UPFs, and defined it. Later on, they would establish a connection between UPFs and weight gain in Brazilian children and adults.
Since that time, researchers have discovered connections between UPFs and a wide variety of health issues, such as coronary heart disease, type 2 diabetes, obesity, gastrointestinal illnesses, and depression, in addition to an earlier mortality rate.
The fact that ultraprocessed foods have become such a significant component of people's diets all across the globe is a cause for worry, according to experts. For example, they are responsible for 67 percent of the calories that children and adolescents in the United States ingest, respectively.
Still, there are a lot of questions. What exactly are the foods that have been ultraprocessed? In addition, how convincing is the evidence that they contribute to harm? In addition to these questions, we asked specialists for answers.
What are the foods that have been ultraprocessed?
Dr. Monteiro and his colleagues established the Nova food categorization system to conduct research on foods based on their processing methods. This system's name comes from the Portuguese and Latin words for "new." Since then, individuals doing studies all across the globe have begun to use it.
There are four categories that the Nova system uses to classify foods:
items such as fresh or frozen fruits and vegetables, beans, lentils, meat, chicken, fish, eggs, milk, plain yogurt, rice, pasta, maize meal, flour, coffee, tea, herbs and spices, and so on, that are either unprocessed or have undergone minimal processing.
Cooking oils, butter, sugar, honey, vinegar, and salt are examples of processed ingredients.
Processed foods are those that combine ingredients from Category 1 with those from Category 2, then preserve or alter them through relatively simple processes like canning, bottling, fermentation, and baking. This category includes freshly made bread, the majority of cheeses, canned vegetables, beans, and fish. These foods may contain preservatives, which extends their shelf life.
Ultraprocessed foods are those that are manufactured using industrial processes and components that are not typically found in grocery shops. These components include high-fructose corn syrup, hydrogenated oils, and concentrated proteins such as soy isolate. It is common for them to include additives such as flavorings, colorings, or emulsifiers in order to make them seem more appealing to the palate. Consider foods such as sodas and energy drinks, chips, sweets, flavored yogurts, margarine, chicken nuggets, hot dogs, sausages, lunch meats, boxed macaroni and cheese, baby formulas, the majority of packaged breads, plant milks, meat replacements, and morning cereals.
"If you look at the ingredient list and you see things that you wouldn't use in home cooking, then that's probably an ultraprocessed food," said Brenda Davy, a nutrition professor at Virginia Tech. "If you see things that you wouldn't use in home cooking, then that's probably an ultraprocessed food."
It is important to note that the Nova system does not categorize meals according to certain nutrients, such as fat, fiber, vitamins, or minerals. According to Maya Vadiveloo, an assistant nutrition professor at the University of Rhode Island, it remains "agnostic to nutrition."
According to Dr. Vadiveloo, this has resulted in a disagreement among nutrition professionals over whether or not it is effective for characterizing the healthfulness of a product. This is in part because many UPFs, such as whole grain breads, flavored yogurts, and newborn formulae, may deliver vital nutrients.
Are foods that have been ultraprocessed harmful?
The majority of data concluding that UPFs are associated with poor health is derived from observational studies. In these studies, researchers interview individuals about their diets and then monitor their health over a period of various years. With the most solid evidence for heart disease-related fatalities, Type 2 diabetes, and common mental health disorders including anxiety and depression, experts claimed that drinking UPFs was connected with 32 health problems in a thorough review of research that was released in 2024. Scientists conducted and published the review in 2024.
Such studies are valuable because they can look at large groups of people—tthe 2024 review included results from nearly 10 million—oover the many years it can take for chronic health conditions to develop, said Josiemer Mattei, an associate professor of nutrition at the Harvard T.H. Chan School of Public Health. She went on to say that the fact that the connection between UPFs and health problems was consistent boosted her belief that there was a genuine concern with the meals.
According to Lauren O'Connor, a nutrition scientist and epidemiologist who previously worked at the Department of Agriculture and the National Institutes of Health, observational studies, on the other hand, have certain drawbacks. She said that while it is true that there is an association between certain foods and chronic illnesses, this does not necessarily suggest that UPFs are directly responsible for an individual's bad health.
Dr. O'Connor questioned whether it is beneficial to classify meals that are so "starkly different" into a single category. Examples of such items include morning cereals and Twinkies. Consuming some kinds of ultraprocessed meals, such as drinks and processed meats, is obviously more hazardous than consuming other kinds of foods. On the other hand, studies have linked the consumption of unprocessed foods (UPFs) like flavored yogurts and whole grain breads to a lower risk of acquiring type 2 diabetes.
According to Dr. O'Connor, clinical studies are required in order to determine whether or not UPFs directly cause health concerns. According to her, there has only been one research project of this kind, and it was a somewhat small one with certain restrictions.
For the purpose of that 2019 study, twenty individuals of varying body proportions resided at a research hospital at the National Institutes of Health for four weeks. They ate mostly unprocessed or slightly processed meals for a period of two weeks, and then for another two weeks, they consumed primarily unprocessed whole foods. Each meal allowed the participants to consume as much food as they desired, while the diets maintained comparable levels of calories and nutrients.
Participants gained an average of two pounds and consumed around 500 more calories per day when following the ultraprocessed diet than they did while following the unprocessed diet. This occurred over the course of the study's two weeks. They lost approximately two pounds while following the raw diet.
This result may help explain the connection between UPFs, obesity, and other metabolic problems, according to Kevin Hall, a researcher at the National Institutes of Health who specializes in nutrition and metabolism and was in charge of the investigation. However, Dr. Hall is currently striving to replicate the research.
It is possible that UPFs are detrimental
According to Dr. Hall, there are a vast number of "strong opinions" on the reasons why ultraprocessed foods are harmful. He continued by saying, "However, there is actually not a great deal of rigorous science" about the systems in question.
According to Dr. Hall, consumer packaged foods (UPFs) are likely replacing better foods in our diets because they are often inexpensive, convenient, and easily available.
Nevertheless, he and other experts believe that the meals could have more direct impacts on health than previously thought. They may be easy to overeat due to the fact that they include mixtures of carbs, sugars, fats, and salt that are difficult to resist, that they are rich in calories, and that they are simple to chew. There is also the possibility that the spikes in blood sugar that occur might cause damage to the arteries or an increase in inflammation. Additionally, it is conceivable that some dietary additives or chemicals could interfere with hormones, induce a "leaky" bowel, or change the flora of the gut.
Researchers like Dr. Hall and Dr. Davy are now testing a number of these hypotheses by initiating preliminary clinical operations. According to Dr. Hall, such research has the potential to assist in determining which UPFs are the most dangerous and perhaps provide tips on how they might be made healthier.
However, the majority of studies believe that there are a variety of ways in which foods are harmful. Dr. Vadiveloo said that it is quite uncommon in nutrition to find a single component that completely explains the connection between meals and a certain health consequence.
Regarding foods that have been ultraprocessed, what should we do?
In 2014, Dr. Monteiro was a contributor to the formulation of new dietary recommendations for Brazil, which recommended that individuals steer clear of foods that were highly processed.
There have been specific recommendations made by other nations, including Mexico, Israel, and Canada, to avoid or restrict the use of ultra-processed foods (UPFs), or "highly processed foods." The United States does not include any such recommendations in its dietary guidelines, but an advisory council is currently researching the potential impact of UPFs on weight gain, potentially influencing the 2025 guidelines.
According to Dr. Hall, it is difficult to know what to do about ultraprocessed foods (UPFs) in the United States since so much food is already ultraprocessed, and individuals with lower means might be particularly reliant on products that belong to this category.
Dr. Mattei further stated, "At the end of the day, they are an important source of food, and food is food." "It is not possible for us to smear anyone," she said.
Expert viewpoints on how individuals should handle UPFs are divergent, despite the fact that the study is still ongoing. According to Dr. Monteiro, the most prudent course of action is to steer clear of them entirely. For instance, you may replace flavored yogurt with plain yogurt that contains fruit, or you could purchase a fresh loaf of bread from a local bakery rather than purchasing packaged bread, provided you have the financial means to do so.
Dr. Vadiveloo proposed a more reasonable technique. This plan would concentrate on reducing the consumption of UPFs that do not deliver important nutrients, such as soda and cookies. Furthermore, she recommended augmenting your intake of fruits, vegetables, legumes, nuts, seeds, and whole grains, irrespective of their ultraprocessing status.
Dr. Davy advises cooking as much as possible at home using minimally processed foods. "At this point, we are unable to express a great deal of information beyond that."
