The term "ultra-processed food" has become shorthand for unhealthy eating, but scientists are increasingly questioning whether this catch-all category actually tells us anything meaningful about nutrition. A major classification system designed to sort foods by how much industrial processing they undergo is now at the center of a heated scientific debate, with researchers arguing that it lumps together foods with wildly different health profiles and may oversimplify what makes certain foods risky.

What Exactly Is an Ultra-Processed Food?

In 2016, researchers at the University of São Paulo created the NOVA classification system to organize foods based on the extent and purpose of industrial processing. The system divides all foods into four categories:

• Unprocessed or Minimally Processed Foods: Plant or animal parts taken directly from nature or altered only minimally, with no added salt, sugar, oil, or fat.
• Processed Culinary Ingredients: Substances used mainly to prepare meals, such as oil, sugar, and salt.
• Processed Foods: Group-one foods with culinary ingredients added to extend shelf life or change flavor.
• Ultra-Processed Foods (UPF): Industrial formulations, typically with five or more ingredients, built from substances rarely used in home cooking and additives meant to alter flavor, texture, and appearance, designed to replace minimally processed foods.

The headline evidence supporting concerns about ultra-processed foods looks compelling. A 2025 meta-analysis pooling data from 18 prospective cohorts with over a million participants and roughly 173,000 deaths found that high ultra-processed food consumers faced a 15% higher risk of all-cause mortality, with each 10% rise in ultra-processed food share adding a 10% increase in mortality risk. However, every study was observational, leaving room for socioeconomic status and other lifestyle factors to confound the relationship even after adjustment.

Why Is the Definition So Problematic?

The deeper issue is that "ultra-processed" isn't a uniform category, so any association depends heavily on a changing definition. This inconsistency is the crux of the entire debate. Nutrition scientist Kevin Klatt has pointed out that NOVA doesn't always track actual industrial transformation. Consider these examples: edamame pasta, made through pulverization and extrusion, could still count as "minimally processed" simply because edamame is its only listed ingredient. A sugar-free gelatin sits in the same NOVA group as a cookie loaded with sugar and saturated fat. Homemade bread with butter and sugar might escape the label, while industrial bread with a trace of emulsifier might not.

The classification system strains particularly in food markets outside Latin America, where it was originally developed. A critical review in Proceedings of the Nutrition Society argues that NOVA works reasonably well in the relatively homogeneous Latin American food systems where it was built, but struggles in other markets, especially with products combining heavy processing and solid nutrition. Australian cereals rich in whole grains get filed as ultra-processed largely because of extrusion. Two popcorns with nearly identical nutrition can land in different categories over natural flavorings alone. Gluten, obtained by simply washing starch out of wheat dough, is treated as having no independent culinary use despite serving as a protein source in several traditions.

What Does the Research Actually Show When You Look Closer?

When researchers split ultra-processed foods into subcategories, the picture becomes much more complicated. A 2024 meta-analysis in Advances in Nutrition confirmed associations between total ultra-processed food intake and diabetes, hypertension, and obesity, but the size of each association varied depending on how diet was measured. A US cohort of more than 206,000 people found that sugary drinks and processed meat were associated with clear cardiovascular risk. At the same time, cereals, baked goods, and yogurt showed neutral or protective associations. A prospective cohort analysis of the European Prospective Investigation into Cancer and Nutrition (EPIC) found the same pattern for diabetes.

This divergence within the ultra-processed food category suggests that processing alone may not explain the health patterns researchers keep finding. Early microbiome research points in the same direction. Different ultra-processed food subtypes may affect gut bacteria in different ways, meaning membership in the ultra-processed category does not guarantee a shared biological mechanism.

There is also a media bias to reckon with. An umbrella review linking ultra-processed foods to 32 health outcomes drew heavy press attention, but the authors judged only four associations convincing: type 2 diabetes, cardiovascular mortality, common mental disorders, and anxiety. Even Kevin Hall's celebrated 2019 trial, often cited as the strongest experimental proof, used diets that differed in fiber, texture, and palatability, not just processing. It shows the diets produced different outcomes, but not which feature caused them.

How Should You Think About Food Processing?

The policy stakes are real and immediate. Ultra-processed foods supply much of the US's dietary fiber, so blanket avoidance could raise diet costs for lower-income households and potentially worsen nutritional outcomes for vulnerable populations. That tension between legitimate scientific criticism and criticism serving industry interests has become personal in the nutrition research community.

A different framing asks not whether NOVA is perfect, but whether its remaining uncertainty is large enough to overturn the conclusions the evidence already supports. Nutrition science is rarely airtight. The UK's Scientific Advisory Committee on Nutrition acknowledges fuzziness around "dietary fiber," yet that concept remains useful. NOVA was never built to measure nutritional quality. Instead, it targets a broader pattern of industrial formulation, using proxies like cosmetic additives because researchers rarely have direct access to manufacturing data. The takeaway is that NOVA and the traditional nutrient-based approach should be treated as complementary rather than competing frameworks.

The real lesson for consumers is that the presence of industrial processing alone doesn't determine whether a food is healthy or unhealthy. A whole-grain cereal with an emulsifier may be more nutritious than a homemade cookie loaded with butter and sugar. Yogurt with added ingredients may support better health outcomes than a sugary drink, even if both are technically ultra-processed. Rather than fixating on processing as the enemy, paying attention to specific ingredients, added sugars, sodium content, and overall dietary patterns remains the more reliable guide to healthy eating.