What are ultra-processed foods and why are they bad for you?

These days, it seems like there is no end to things that can harm you: vaping, social media, sitting for long periods of time, too much sun, too little sun. Now, a growing body of research suggests that the majority of foods Americans eat every day may be linked to a huge range of diseases and disorders.
I’m talking about ultra-processed food.
We’ve known for a few decades that something about modern, prepackaged foods leads to negative health impacts. In the 1980s, as breakneck globalization ushered in a new world where mass production reached more people than ever before, diets around the world changed, too. In the early 2000s, nutritional epidemiologist Carlos Augusto Monteiro was studying dietary habits of fellow Brazilians. He and his team studied associations between breastfeeding and obesity and the impact of income and education on fruit and vegetable consumption. Importantly, Monteiro was also tracking changes in both the prevalence of chronic diseases and changes in Brazilian diets.
One study, in which Monteiro and his colleagues studied data on dietary habits from 1987 to 2003, found that the consumption of traditional foods such as rice and beans had declined while the consumption of processed food items such as store-bought cookies and soda had increased, in some cases by more than 200 percent. Monteiro and his team had captured, in real time, a trend that has taken place in nearly every developed country in the world: a huge increase in the consumption of what Monteiro later termed “ultra-processed foods” alongside a parallel rise in obesity and chronic diseases.
Ultra-processed foods, or UPFs for short, are those prepackaged foods that can be forgotten in your pantry seemingly forever and still taste great when you happen upon them. UPFs are your sodas, potato chips, granola bars, protein bars, protein powders, instant noodles, candy, and even most types of store-bought bread. These foods are already innately familiar to anyone who has ever stepped foot into a grocery store, a gas station mini-mart, or a fast food restaurant.
Today, the average American consumes some 60 percent of their calories from ultra-processed foods; some studies found that number to be higher among children. UPFs tend to be calorie-dense, high in fat and sugar, and easy to overconsume, so it’s not surprising that eating more of these foods has long been linked with increasing prevalence of obesity, diabetes, and high blood pressure.
But emerging research has also linked UPF consumption to other diseases and disorders, including depression, anxiety, inflammatory bowel disease, and autoimmune disorders. Studying the impacts of nutrition on human health is notoriously tricky given how so many factors — such as race, income, genetics, and the like — can play a role. However, according to researchers and epidemiologists, when you look across all the available research together, there is an overwhelming sense that UPFs negatively affect human health.
To be clear, almost all of the food we eat is processed in one way or another, but there is a sliding scale of food processing. We cook meat; pasteurize milk and eggs to kill harmful bacteria; can vegetables to store and preserve them. Processing not only makes food safer to eat, it allows us to spend less time and energy feeding ourselves each day.
When you cook, pickle, or cure foods, they largely retain their original identity — steamed broccoli still looks nearly identical to raw broccoli. Ultra-processed foods, however, are made of ingredients that are extracted from whole foods through a series of industrial processing steps and then recombined with additives to give you this whole new food that’s shelf-stable.
It seems that somewhere in all this food processing, food can become harmful. But the jury — or science, rather — is still out on exactly how that happens. Despite the still-emerging scientific evidence, it seems that reducing UPF consumption could improve your health. But, to make things more complicated, we live in a food environment where UPFs are not only aggressively marketed to us from a young age, but also are often the only affordable and accessible option for millions of people.
Though we refer to UPFs as “foods,” common definitions imply that they are more akin to chemical concoctions that happen to be edible. In September 2016, the Global Panel on Agriculture and Food Systems for Nutrition defined UPFs as industrialized formulations, depleted in crucial nutrients like fiber and protein.
Not all processed foods are made equally, though. A number of different classification systems describe different levels of food processing. Per one system, the NOVA classification, which Monteiro devised, there are four categories. Here’s the breakdown:
Let’s walk through an example of how an unprocessed food transforms into a UPF.
Take, for example, corn. Through a series of industrial processing steps, corn can be broken down into corn protein, corn fiber, corn fat, and cornstarch, explained Chris van Tulleken, an infectious diseases physician and author of the book Ultra-Processed People. Additional processing can transform these ingredients into others. Cornstarch, for instance, can be heated with hydrochloric acid to make corn syrup. These ingredients are then combined piecemeal with varying amounts of sugar, oil, and flour to make everything from Twinkies and spreadable cheese to certain types of peanut butter, hot dogs, and Doritos.
When ingredients are processed, some of the natural fibers, vitamins, and minerals they contained are lost. This means that these piecemeal ingredients also require a whole slew of additives to keep them together or to make them more palatable. Additives are artificial colors and flavors; foaming and anti-foaming agents; bulking ingredients; and emulsifiers. Vitamins and minerals are also sometimes added back during processing.
These additives are a hallmark of UPF and an easy way to determine if what you are eating is ultra-processed or not. “The main way of telling is if the food contains an additive, which you don’t normally find in a domestic kitchen,” van Tulleken explained. Unless you work at a Michelin-starred restaurant or have some niche interest in gastronomy, you probably don’t have maltodextrin or tartrazine sitting in your cupboards at home.
The hard thing about nutrition science is that it’s notoriously difficult to untangle all the different things that impact health on top of understanding why people make the food decisions they do. Where you grew up, how much money you make, and genetics can all factor into health and nutrition. Because of this complexity, researchers cannot design experiments where they manipulate each of these factors one by one and see what effect that has on health. Instead, scientists rely on observational studies, collecting demographic data and information about the dietary habits of participants including their UPF consumption.
But even collecting data on dietary habits is challenging. “In nutrition, what makes it even harder is that diet is so extremely complex,” explained Filippa Juul, a nutritional epidemiologist at New York University.
“If we think about what any given person eats in a day, they eat a variety of foods, they eat them in different combinations, they eat them in different amounts, at different times of the day,” Juul said. “We may have eaten differently in different stages of our lives, or we’ve been exposed to something for a longer time or shorter time. It is very hard to tease apart all of those things in a research study.”
With all this complexity, researchers look to see whether, over many studies, there is a general trend that UPF consumption is linked to poor health irrespective of age, gender, education, or other factors. And for a lot of health conditions, the evidence overwhelmingly indicates that UPFs are bad for health. “The evidence around UPF is incredibly robust,” van Tulleken said. “We’ve got strong associations, and they’re very consistent, found by multiple research groups around the world.”
The strongest data shows that increased UPF consumption is associated with a higher risk of developing cardiovascular disease, type 2 diabetes, depression, and anxiety.
Some studies have even identified a possible link between UPF consumption and cancer. One study published last year that followed nearly 200,000 British adults for up to 12 years found that every 10 percent increase in UPF consumption was associated with a 6 percent increased risk of mortality from any type of cancer, including a 16 percent increase of dying from breast cancer and a 30 percent risk of dying from ovarian cancer.
Given this overwhelming evidence linking UPF to a myriad of diseases and ills, one big question looms: What exactly do ultra-processed foods do to the body to make it susceptible to all these diseases? In short, scientists don’t yet know. But they have some plausible theories.
One is that UPFs are intentionally made to be addictive. Specific combinations of salt, sugar, fat, and carbohydrates are considered “hyperpalatable,” and trigger the brain’s reward system in the same way that addictive drugs do. UPFs are also low in satiating nutrients such as protein and fiber, again making it easy to overeat these foods. When you consume a lot of UPF, you are consuming a lot of sodium, saturated fats, and sugar, which may then lead to high blood pressure, type 2 diabetes, and obesity.
UPFs may also cause hormonal changes or alter the gut microbiome. “At this stage, we’re awash in plausible mechanisms,” said Kevin Hall, the section chief of integrative physiology at the National Institute of Diabetes and Digestive and Kidney Diseases. “I don’t think we know all the different mechanisms by which ultra-processed foods might exert on poor health outcomes.”
One other unknown is the impact of specific types of foods. Are some UPFs worse than others? What about plant-based meat alternatives, such as the Beyond Burger or the Impossible Hot Dog, which some experts categorize as UPFs? In most studies, researchers lump all UPFs together, so it isn’t clear if certain UPFs are driving the association between their consumption and poor health. You might recall a few headlines back in June saying that plant-based proteins are linked to heart disease; the study the headlines were based on looked at a large population group and only had 0.2 percent of calories stemming from plant-based meats. By grouping plant-based meats with breads, pastries, and the like, we’re not getting a clear picture of the actual relationship between meat alternatives and health. That’s one area where research can improve, especially since other studies suggest that because plant-based meat is lower in calories, saturated fat, and cholesterol, it may be better for health than unprocessed meats.
Despite the need for more research, van Tulleken doesn’t necessarily think we need to parse out every single detail before deciding that there needs to be a big shift in what foods most people consume.
To make things even more complicated, we live in a food environment where eating healthy, unprocessed foods is challenging. UPFs are aggressively and constantly advertised to us, and especially to children. UPFs are convenient and sometimes more readily available than fresh foods.
Cutting UPFs from your diet is certainly one way to go about preventing any potential harms to your health. But for many people, particularly low-income individuals or those living in food deserts where UPF is the only affordable food option around, this may not be realistic. UPF tends to be much cheaper than fresh produce and meat. One study found that, on average, UPFs cost 55 cents per 100 calories whereas unprocessed or minimally processed foods cost $1.45 per 100 calories. That can add up. Here is a back-of-the-envelope calculation: If you’re feeding a household of two adults at roughly 2,000 calories per day, a diet composed entirely of UPF would cost about $154 per week while a diet of minimally processed or unprocessed foods would cost $406 per week.
Ultimately, nutritionists, physicians, and other public health researchers advocate for a broader sea change in our food environment. For one, we need to ensure that everyone has reliable access to affordable fresh, unprocessed foods. Eliminating poverty and socioeconomic inequality would accomplish this, but since that often seems like a far-off target, there are other, more viable approaches. One way to do this might be to strengthen local food production systems so that stores don’t have to rely on food shipped into communities from far away or even foreign countries, racking up transportation and storage costs along the way.
Changes in policy and regulation could also help. Federal and state governments can start by overhauling school lunch programs which often feature a huge array of UPF, such as Lunchables. Another high-priority target is advertising. One hallmark of UPF is that it is aggressively marketed with all sorts of false and misleading health and nutrition claims. Mandating that UPF products are clearly labeled with accurate descriptions of their health benefits and harms is a starting place.
In short, if we are serious about improving the health of everyone and not just the select few, solid scientific evidence is just the beginning. Societal-wide solutions will require action from everyone including corporations, consumers, and politicians.
“My interest is in creating an environment where everyone can eat like rich people do. At the moment, we live in a food apartheid,” van Tulleken said. “Everyone should be able to afford good, healthy food. And if you then choose to drink a can of phosphoric acid and non-nutritive sweeteners, well, good for you. It should just have some warning labels.”