What You Need to Know About Ultra-Processed Foods

Traditional food processes like cooking, fermenting, and preserving have been a part of our culture and evolution as a human species. But a new category known as ‘ultra-processed’ foods (UPFs) has recently gained significant attention for all the wrong reasons.

When examining food labels in the supermarket, you may notice ingredients such as emulsifiers, preservatives, sweeteners, and artificial flavours—components typically found in ultra-processed foods; not in your home kitchen.

These ingredients are found in an array of different foods. Many breakfast cereals, flavoured yogurt, soft drinks, sausages, and mass-produced packaged whole grain bread are all typical examples of UPFs. These foods may help to understand why in Europe the proportion of diets consisting of UPFs ranges from 13% to 43%, with some estimates reaching as high as 60%. But, despite being associated with various health problems, food companies argue that their products are nutritionally complete and can support a healthy diet.^1,2

So, what are ultra-processed foods, why is everyone talking about them, and should we be concerned?

What are ultra-processed foods?

To understand where the concept of ‘ultra-processed’ foods began, we need to take a short trip back in time to mid-1990s Brazil. Here, a Brazilian nutritional epidemiologist named Carlos Monteiro observed a concerning trend in his country: childhood obesity rates were climbing at an alarming rate.³

Monteiro and his team at the University of São Paulo dug into data on Brazilian household food purchases to uncover shifts in dietary habits. Their analysis revealed a significant decrease in the consumption of traditional ingredients like rice, beans, cooking oils, salt and sugar alongside a marked increase in the intake of highly processed foods such as sodas, sausages, instant noodles, packaged breads, and biscuits.⁴

To describe the rise in processed food consumption, Monteiro and his colleagues coined the term "ultra-processed foods" and defined them as “formulations of ingredients, mostly for industrial use, made through a series of complex processes, often requiring advanced equipment and technology.”

The NOVA food classification system

Understanding the effects of food processing on health requires detailed analysis with clear definitions and distinctions. To help in this, Monteiro and his team developed the ‘NOVA food classification system’, which categorises foods into four groups based on their level of processing.^4,5

Group 1: Unprocessed or minimally processed foods

These are the edible parts of plants and animals, such as fruits, vegetables, eggs, and milk. These foods might have undergone very basic processing that you could easily do at home, like drying herbs, grinding coffee, chopping carrots or pickling vegetables. This category also includes foods like dried or fresh pasta and white rice, which undergoes milling to remove the husk, bran, and germ.⁶

Group 2: Processed culinary ingredients

These food items, sometimes sourced from Group 1, have undergone further industrial processes that you likely wouldn't do at home, such as centrifuging, refining, or extracting. Foods in this category include oils, syrups, sugars, and cornstarch. These ingredients are generally used to prepare, add flavour to, and cook foods from Group 1.

Group 3: Processed foods

These foods are usually a combination of Group 1 and Group 2, processed into simple or traditional foods that are ready to eat. Examples include cheese, traditional sourdough bread, cured meats and fish, salted nuts, and fruit in syrups. Between Groups 1, 2, and 3, you can create most of your typical home-cooked meals.

Group 4: Ultra-processed foods

This food group is made up of snacks, drinks, ready meals and many other product types formulated mostly or entirely from substances extracted from foods or derived from food constituents. Ultra-processed foods use various additives to mimic or enhance the taste, texture, or appearance of natural foods. They contain ingredients such as hydrogenated fats, high fructose corn syrup, and protein isolates, not commonly found in your home kitchen. Examples include packaged snacks, many breakfast cereals, energy drinks, sliced meats like ham and salami, microwave meals, chicken nuggets, ready-made pasta and pizza dishes, and many instant, 'slimming,' or low-fat products, margarine and mass-produced bread with refined flours.

The science behind ultra-processed foods

After their pioneering work on UPFs, Carlos Monteiro and his team linked these foods to weight gain among both children and adults in Brazil. Since then, research has associated UPFs with a variety of health issues, including heart disease, type 2 diabetes, obesity, gastrointestinal disorders, depression, and even premature death.⁷

But what underpins these studies, and can we make sweeping statements about all UPFs? For example, mass-produced or packaged wholemeal bread is considered ultra-processed, but does that mean we should avoid it altogether?

Unpacking the health impacts of ultra-processed foods

A recent study, which made headlines worldwide, linked UPFs to 32 harmful health effects. This "umbrella review" analysed numerous studies involving nearly 10 million people, making it the most comprehensive examination of UPFs' health impacts to date. The results varied, with some studies showing weak correlations, likely because UPFs encompass a wide range of foods.⁷

These studies typically involve large groups of people who report their regular eating habits and health status. Researchers then adjust the data for factors like age, gender, and lifestyle, which might influence the results. However, these studies can only show a relationship between diet and health; they don’t explain how or why certain foods cause health issues. To truly understand the effects of UPFs, more detailed research is needed.

This is where controlled studies come in, often providing more compelling evidence. Kevin Hall, a researcher at the National Institutes of Health (NIH), conducted a four-week study with 20 healthy adults, assigning them to an ultra-processed and minimally processed diet for two weeks each.⁸ The ultra-processed diet included meals like canned ravioli and hot dogs, while the minimally processed diet featured fruits, vegetables, and unprocessed meats. Both diets were nutritionally matched, and participants could eat as much as they wanted. Surprisingly, during the ultra-processed diet, people consumed about 500 more calories daily and gained weight, while they ate less on the unprocessed diet and lost weight.⁹

Other studies have examined health and nutrition data over extended periods, often finding a correlation between ultra-processed food consumption and diseases like cancer or Alzheimer's.^10,11 These studies suggest that the higher the percentage of UPFs consumed, the higher the risk for poor health in the future.

Negative effects are suspected, but hard to prove

However, many of these studies only show correlations and don't actually prove that UPFs directly cause these health issues. As a result, there are still many strong opinions on why UPFs are considered unhealthy, but little rigorous science explaining the specific biological mechanisms involved.¹² For example, data from the European Food Safety Authority found no connection between increased ultra-processed food consumption and increased BMI.² Similarly, emulsifiers, common ingredients in UPFs, have been linked to gut microbiome disruption and an increased risk of cardiovascular disease.¹³ However, conclusive evidence showing how these ingredients cause these effects has not been published.

Defining UPFs as a separate food category

One of the biggest criticisms of the ultra-processed food category is that some foods classified as ultra-processed are also considered healthy. Foods like wholemeal bread, low-fat (unflavoured) yoghurt, and wholegrain breakfast cereals often fall into the ultra-processed category, yet are widely regarded as common staples in a healthy diet. On the other hand, many foods high in fat, salt, and sugar, which should generally be limited, also fall into the ultra-processed category.¹⁴

While the research isn’t clear on the causes of health impacts associated with UPFs, there is no ambiguity about the fact that not all UPFs are equally detrimental to our health. Unlike wholemeal bread or yoghurt, certain categories, like sugary drinks and processed meats, have well-documented negative health impacts. This suggests that the key is not to demonise all UPFs but to discern which specific types are harmful.

Importantly, a high-quality diet—rich in fruits, vegetables, whole grains, and healthy fats—can mitigate the potential risks associated with UPFs. Therefore, sweeping advice to avoid all UPFs could disproportionately affect low-income individuals who rely on affordable and convenient foods like supermarket wholemeal bread, which also contribute essential nutrients such as fibre.¹⁵

Conclusion

In 2014, Dr. Monteiro co-authored Brazil's dietary guidelines, advising people to avoid ultra-processed foods when possible. Similarly, countries such as Mexico, Israel, and Canada have recommended limiting or avoiding UPFs. In the United States, current dietary guidelines do not address ultra-processed foods, but an advisory committee is investigating their impact on weight gain, which may affect the 2025 guidelines.⁴

The sensationalism surrounding UPFs can obscure the need for targeted government regulations to curb the marketing and sales of genuinely unhealthy foods high in sugar, salt, saturated fats, and calories, and to help those in poverty access and afford healthy food.

Research on UPFs also highlights the importance of pinpointing harmful components within these foods so manufacturers can reformulate products, much like they did with trans fats and artificial colours.¹⁶

While future research might further clarify which processing methods are most harmful, the current evidence suggests a more nuanced approach. Instead of fixating on the UPF label, it is more practical to focus on consuming a variety of whole foods, such as fresh produce, legumes, lean meats, and whole grains. This balanced perspective can help avoid unnecessary fear while promoting better overall dietary habits.¹⁵

Read more about the unequal access to healthy food in: Food Deserts | Why Do They Exist