Why Ultra-Processed Foods Are So Bad for You

Most people recognize that a nutritious diet promotes a healthy life, but navigating the wide range of options at your grocery store isn’t always straightforward—especially when so many foods are advertised as healthy (but aren’t).

A growing number of recent studies have raised health concerns about a certain type of food that most Americans eat: ultra-processed foods. One such study, published in November 2022 in the American Journal of Preventive Medicine, concluded that these foods likely contributed to about 10% of deaths among people 30 to 69 years old in Brazil in 2019. Other studies—including one published in Neurology in July 2022 finding that a 10% increase in ultra-processed food consumption raises the risk of dementia—have linked the food category to severe health outcomes.

Unlike minimally processed food or unprocessed foods—like eggs, for example, which travel from the farm to your kitchen looking pretty much the same—ultra-processed foods have been radically changed by manufacturers. By the time they hit your grocery shelf, they’ve likely been heated, pressed, and enhanced by additives designed to make them last longer, taste better, and appear more attractive, often to the detriment of your health. Here’s what you need to know about ultra-processed foods.

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What are ultra-processed foods?

Ultra-processed foods are “made mostly or entirely from substances derived from foods and additives,” write the authors of a 2017 commentary published in the journal Public Health Nutrition. These additives are ingredients not usually used in home cooking, like preservatives, dyes, and non-sugar sweeteners.

This definition covers a wide range of foods in your local grocery store—from instant soup to packaged snacks to certain meat products, including sausages, burgers, and hot dogs. Such foods tend to have telltale signs, says Tim Spector, a professor in genetic epidemiology at King’s College London and author of Food for Life: The New Science of Eating Well. Typically, he says, they have a very long shelf life and 10 or more ingredients, which often include “products that you wouldn’t find in your kitchen or you can’t understand.”

They’re distinct from how some nutrition researchers define processed or minimally processed foods. These foods tend to contain just two or three ingredients— usually a whole food plus salt, oil, or sugar—and have often been preserved, cooked, or fermented. Some of these foods include canned fish, fruit in syrup, cheese, and fresh bread.

But not all ultra-processed foods are equally unhealthy. Fang Fang Zhang, chair of the division of nutrition epidemiology and data science at Tufts University, notes that whole grain, ultra-processed foods—like some packaged breads—are an important source of fiber for many people. “Even with ultra-processed food…whole grains are a better choice than refined grain,” says Zhang.

Researchers at Northeastern University have also created a tool for comparing packaged foods in the same category in order to choose the one with the least amount of processing. For instance, in the yogurt category, one plain organic yogurt scored a 4/100 (a favorable score indicating a low amount of processing), while Oui Petite by Yoplait received a maximally processed score of 100.

Why are ultra-processed foods so harmful?

Longitudinal studies in the Americas and Europe have linked eating more ultra-processed food to a number of health risks, including increases in obesity, high blood pressure, Type 2 diabetes, and even dementia. Other research, including a pair of studies in the BMJ by researchers in Spain and France, has linked consuming ultra-processed foods to an increased risk of early death.

Ultra-processed foods tend to be junk food: low in fiber and high in sugar and calories, says Zhang. But because ultra-processed foods are defined by the types of ingredients they contain, not by their nutrition content, this category can also include foods with beneficial nutrients, like breads high in fiber.

Scientists who research ultra-processed foods say that there seems to be something about the processing itself—not just the nutrition content—that makes them unhealthy. In one 2019 study that supports this idea, researchers split 20 people into two groups and controlled what they ate for two weeks. Each group ate meals with identical quantities of calories, sugar, fat, fiber, and micronutrients, but one group ate a diet of ultra-processed food, while the other ate unprocessed food. In the end, the people who ate ultra-processed food gained weight, while those who ate unprocessed food lost weight.

Researchers have raised several theories to explain this. One, says Eduardo A.F. Nilson, a researcher at the Center for Epidemiological Research in Nutrition and Public Health at the University of São Paulo who co-authored the Brazilian study, is that eating ultra-processed foods changes the way people eat overall: replacing homemade food with ready-to-eat, energy-dense foods that are easier to overeat. “They are made, by design, for overconsumption,” says Nilson. “They have hyper-palatability. We say they have ‘hyper-flavors’—they will be very sweet, very salty…and because they are ready to eat, they will replace traditional diets.”

Another idea, says Spector, is that ultra-processed food spurs people to eat too quickly. Spector and other scientists are also investigating whether the problems start after ultra-processed food reaches your gut. Spector says that in his research, he’s found that some of the chemicals in ultra-processed foods—especially emulsifiers, which are added to food to help mix substances—disrupt gut microbes, which scientists theorize send signals to the brain when you’ve had enough to eat. “Either it sends signals to the brain or to the gut microbes to eat more, or it’s simply that the food is so easy to eat that it gets into the system so fast that you don’t have time to get your fullness signals in the brain,” says Spector.

Not everyone agrees that all ultra-processed foods are dangerous

Critics, including Gibney, argue that the ultra-processed food category is too broad to be useful as a scientific concept. In Gibney’s view, the category of ultra-processed food incorporates too many different kinds of food, and villainizes too large a range of ingredients—including food additives, like preservatives, that public-health authorities have deemed to be safe. He argues that these problems undermine nutrition research, because it’s difficult to standardize which foods are included in studies.

Another problem, says Gibney, is that the concept of ultra-processed food discounts the importance of reformulating food, such as by making it whole grain or lower in sugar, which he says has helped to make processed food healthier. For many people, he adds, eliminating processed food just isn’t realistic, as it makes up too much of their diet, and they don’t have the time or money to cook every meal. “Ultra-processed food as a concept is providing a simple, popular answer to what is a very complex question,” says Gibney.

How do I cut back on ultra-processed foods?

Experts agree that reducing consumption of ultra-processed foods shouldn’t be the public’s responsibility alone. Many people don’t live in communities with access to healthy, minimally processed food, which tends to be more expensive than ultra-processed food, says Nilson. To reduce ultra-processed food, Nilson argues that the government will need to implement policies to expand access to healthy food, such as by limiting the availability of ultra-processed food in schools.

Another important policy, says Nilson, is for the government to warn the public about the dangers of ultra-processed food and to implement clear labeling. Some countries have already started to warn the public about ultra-processed foods. In 2022, for instance, Canada announced new labeling requirements for pre-packaged food, including labels when such products are high in sodium, sugars, or saturated fat, and Health Canada incorporated warnings about highly processed food into its online healthy food choices guide.

If you want to make your own diet healthier, Spector says a mindset change is key. “We just need to get people thinking about food not in a calorie way, and think about the quality,” he says. If you want to reduce the number of ultra-processed foods you eat, Spector suggests opting for other foods that are cheap and don’t take much preparation, like beans, lentils, and eggs. For snacks, he suggests nuts, seeds, and whole fruit. “Try going off [ultra-processed food] for a week,” he says, “and see what happens.”