Are ultra-processed foods a public health hazard?

Short answer: Very likely yes—but with important caveats about causation and mechanism

The evidence is substantial and growing, but scientists are still debating why ultra-processed foods (UPFs) are harmful, not whether the associations are real.

What counts as a UPF

UPFs are classified using the NOVA system, which groups foods by processing extent rather than nutrient content. Ultra-processed foods and drinks belong to the fourth NOVA category, characterized by industrial formulations with five or more ingredients. They are defined as industrial formulations made by deconstructing whole foods into food-derived substances (e.g., fats, sugars, starch, protein isolate), altering them, and recombining them with additives, like colors, flavors, and emulsifiers into products. Typical examples are soft drinks, fast foods, chicken nuggets, instant soups, fruit drinks, and flavored yogurts.

The evidence for harm is strong and consistent

A major 2024 umbrella review of 45 meta-analyses covering roughly 10 million participants found "convincing" evidence that a diet high in ultra-processed foods increases the risk of death from cardiovascular disease by 50% and the risk of anxiety by 48%. It also found "highly suggestive" evidence that greater consumption of these foods increases the risk of death from heart disease by 66%, the risk of obesity by 55%, sleep disorders by 41%, Type 2 diabetes by 40%, early death from any cause by 21% and depression by 20%.

More recent 2025 reviews have reinforced these findings: additional umbrella reviews from 2025 found similar results, reinforcing associations between UPFs and all-cause mortality, cardiovascular disease incidence and mortality, Type 2 diabetes incidence and colorectal cancer. A 2025 meta-analysis specifically found a 13% higher diabetes risk for each 10% increase in UPF consumption.

Crucially, randomized controlled trials now show causation, not just correlation

This is the biggest recent development. A 2025 RCT demonstrated harmful effects of UPFs on weight gain and metabolic and reproductive health, regardless of excessive caloric intake. More broadly, controlled trials show UPF-rich diets increase energy intake and weight gain, with mechanisms including high energy density, disrupted food matrices, faster eating rates, additives affecting gut, and hyper-palatable formulations.

Emerging 2025 research has also linked UPF consumption to cognitive decline, stroke, and early signs of Parkinson's disease, based on large cohort studies tracking tens of thousands of adults.

Where evidence is weaker

Not every claimed harm holds up equally well. The 2024 umbrella review found weak to no evidence for many site-specific cancers, including breast, central nervous system, chronic lymphocytic leukemia, pancreatic and prostate cancer, as well as for conditions such as hypertriglyceridemia, low HDL cholesterol, Crohn's disease, ulcerative colitis, hyperglycemia, metabolic syndrome and non-alcoholic fatty liver disease. Cancer risk overall remains generally site-specific and less consistent than those reported for cardiometabolic outcomes.

The scientific debate: Is it processing itself, or just bad nutrition?

This is where real controversy exists. Critics argue the NOVA classification is flawed: many aspects of food processing can affect health outcomes, but conflating them into ultra-processing is unnecessary because the main determinants of chronic disease risk are already captured by existing nutrient profiling systems—and Nova classification characterizes several healthy, nutrient-dense foods as unhealthy. This camp argues effects are better explained by conventional factors—grain refinement, low fiber content, high glycemic index, and high energy density—rather than processing per se.

On the other side, a 2025 American Heart Association advisory took a middle position, suggesting these associations largely reflect high intake of nutritionally poor UPFs that overlap with foods rich in unhealthy fats, added sugars, and sodium, while noting the need for further research to disentangle the potential roles of additives and food matrix alterations.

However, some evidence pushes back against the "it's just bad nutrition" explanation: a large review of 37 cohort studies suggests that the observed negative association between UPFs and health outcomes cannot be explained by poor diet quality alone.

Bottom line

UPFs are increasingly recognized as a genuine public health concern—the scale of evidence (observational and now experimental/RCT data) is large and remarkably consistent across cardiovascular disease, type 2 diabetes, obesity, mental health, and all-cause mortality. Global consumption is rising rapidly, with UPFs now contributing over half of total calorie intake in the U.S. The main scientific uncertainty isn't whether high UPF diets are harmful, but which specific mechanisms—nutrient profile, additives, food matrix disruption, hyper-palatability driving overeating, or some combination—are driving the harm. This matters for policy: if it's mainly about sugar/salt/fat content, nutrient-based regulations may suffice; if processing itself (additives, matrix changes) is independently harmful, broader restrictions on industrial formulation may be needed.